The Utilization in Sculpture of Ceramic Shell Piece Molds for Specific Nonexpendable Materials

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THE UTILIZATION IN SCULPTURE OF CERAMIC SHELL PIECE MOLDS FOR SPECIFIC NONEXPENDABLE MATERIALS

DISSERTATION

Presented to the Graduate Council of the North Texas State University in Partial Fulfillment of the Requirements

For the Degree of

DOCTOR OF PHILOSOPHY

Ronnie J. Garcia, B. A., I. M. A.

Denton, Texas May, 1977

WNW, 0 1977

RONNIE JOSEPH GARCIA

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Garcia, Ronnie J., The Utilization in Sculpture of Ceramic Shell Piece Molds for Specific Nonexpendable Ma terials. Doctor of Philosophy (Art), May, 1977, 106 pp., 59 illustrations, bibliography, 43 titles.

This investigation was concerned with developing a procedure for using nonexpendable pattern materials in ce ramic shell piece molds. Literature relating -to this study indicated that nonexpendable materials, used in whole ceramic shell molds, had been limited to frozen mercury. Furthermore, ceramic shell piece molds designed specifically to accomodate nonexpendable materials had not been described. Nonexpendable materials in ceramic shell piece molds would provide the sculptor with additional pattern material for ceramic shell investment, and greater flexibility in manip ulating surface textures.

Development of this procedure was related to other considerations. Among these were the identification of non expendable materials that could be removed from ceramic shell molds without damaging the mold inner face, effective dewaxing time and temperature for ceramic shell piece molds, surface quality of metal casts resulting from the use of nonexpendable patterns, and the functional role of the ce ramic shell piece mold in metal casting. The two nonexpend able materials identified in this study were acrylic polymer

MRWill paint and aluminum.

The investigation was divided into the pilot study and the principal experiment. The pilot study pointed out that aluminum and the ten tested acrylic polymer paints left

excessive debris in the mold after flash dewaxing. Ceramic

shell piece molds were designed and used to accomodate the

identified nonexpendable materials and to facilitate debris removal after dewaxing. The principal experiment tested acrylic polymer paint and aluminum, combined with wax in

two different piece mold configurations. These config urations were designed for flat patterns, and hollow cyl indrical patterns, and varied significantly in size, weight, design, and metal carrying capacity. Patterns were molded in ceramic shell, flash dewaxed, and cast in silicon bronze. Metal casts of each pattern were examined for accurate re production of original detail. A procedure of utilizing ceramic shell piece molds for nonexpendable materials was developed by this investigation.

Wax shim lines are first incorporated into each pattern.

These patterns, combined with aluminum and/or acrylic poly mer paint, are molded in ceramic shell. The mold border over the wax shim is then crushed or cut to expose the edge of the wax shim line. Nichrome wires are pushed into the wax shim line. The mold is then wrapped loosely with ni chrome wire, and placed in a dewaxing furnace maintained at temperatures for normal dewaxing. Dewaxing causes the mold to split in half at the shim line. After dewaxing, the

molds are opened, cleaned with a stiff brush, and rejoined with thickened ceramic shell slurry. Woven fiberglass rov

ing is applied for reinforcement. The mold is preheated and cast in the same manner as conventional ceramic shell molds.

Casts exhibiting very good reproduction of the original pat

tern are produced when the procedure described is followed. Results of the investigation recommend that larger and

more complex three dimensional forms be used with the ce ramic shell piece mold, additional nonexpendable materials

be studied, other rejoining methods be explored, and expense of the process be reduced. It is also recommended that a

bank of information on the ceramic shell process be estab lished by universities for student use, and that the ceramic

shell process be included in undergraduate sculpture courses. Finally, it is recommended that research on ceramic shell begin on the graduate level.

The report is organized into five chapters including

the introduction, review of related literature, pilot study, principal experiment, and summary, conclusions, and recom mendations. TABLE OF CONTENTS

Page LIST OF ILLUSTRATIONS v Chapter

I. INTRODUCTION...... I Statement of the Problem Scope and Delimitations Significance of the Study Definition of Terms

II. A REVIEW OF RELATED LITERATURE...... * 11 The Croning Mold The Ceramic Shell Mold

III. PILOT STUDY. .**...... 23 Pilot Study Test I: Flash Dewaxing of Wax Patterns Coated with Identified Acrylic Polymer Paint Pilot Study Test II: Piece Mold Sep aration and Rejoining Pilot Study Test III: Modification of Sprue and Air Vent Systems on Wax and Aluminum Patterns Coated with Identified Acrylic Polymer Paint Synthesis of Major Findings of the Pilot Study

IV. PROCEDURAL TECHNIQUES FOR CERAMIC SHELL MOLDS . 63 Pattern Type Selection Sources of Data Procedure Analysis of Data

V. SUMMARY AND CONCLUSIONS...... 93 Conclusions Recommendations for Further Study

BIBLIOGRAPHY ...... 103

iv LIST OF ILLUSTRATIONS

FiEgure Page I. Steps in Ceramic Shell Coating Procedure . . . . 2

2. General Mold Configurations Used in Pilot Study . 25

3. Mold Fragment of Pilot I-1 ...... 30

4. Mold Fragment of Pilot I-1- . . . . - . . . 30 5. Comparison of Pilots 1-2, 1-3, and 1-4 . . . . 31 6. Completed Wax Pattern of Pilot 11-2 . . . . . 34 7. Pilot 11-3 Pattern after Straw and Paint Application ...... 36 8. Pilot 11-2 after Completion of Molding . . . . 38 Pilot 11-2 9. after Crushing of Mold -0 - - - 38 10. Metal Cast, Pilot 1-1 . . 40

11. Metal Cast of Pilot 11-2 . . 42 12. Intact Metal Cast of Pilot 11-3 . . 0 . 0 . . 42 13. Mold of Pilot 11-2 after Dewaxing ...... 44

14. Separation of Ceramic Shell Mold * . . . . . * . 44 Mold Wall 15. of Pilot 11-2 ...... , 0 S , 45 ------45 16. Mold Wall of Pilot 11-2 . . - 0 Mold 17. Wall of Pilot 11-3 ...... 46 18. Mold Wall of Pilot 11-3 . . . . 0 0 ...... 46 19. Cast of Pilotll1-2 ...... 0 0 0 . . 0 0 49 20. Cast of PilotlII-2 . . . . . 0 0 P P .0 . , 49 0-0p 50 21. Mold of Pilot 11-3 after Casting a - 0 -

V Figure Page

22. Cast of Pilot 11-3 ...... - - -0-*-0 - - . 51

23. Cast of Pilot 11-3 . . . . &-. - - - -- * . - 51 24. Diagram of the Position of the Sealed Mold During Vertical and Horizontal Pour . I .. .53

25. Pattern Design Changes ...... 0- .54

26. Pilot III-1 Ready for Molding ...... 56

27. Mold of Pilot III-1 after Casting ...... 58

28. Mold of Pilot 111-2 after Casting . . . . . 0 . .58

29. Cast of Pilot III-1 ...... - . . . - 0 0 59

30. Cast of Pilot 111-2 ...... 59

31. End View of Wax Pattern of FP...... 66

32. Top View of Wax Pattern of CP...... 66 33. FP Coated with Polymer Paint ...... 68 34. CP Coated with Polymer Paint4. .s.i . . . . . 68 35. Closeup of Paint/wax Seal of CP ...... 69 36. Front View of EP after Molding is Complete 71

37. Front View of CP after Molding is Complete . . .71 38. Crushed Edge of Mold of FP ...... 72 39. Closeup of Mold of CP ...... 72 40. Back Side of FP Mold ...... 74

41. Crushed Mold of CP ...... 74

42. Edge of Crushed Mold Border of FP ...... 75

43. Exposed Lower Wax Shim Line of CP ...... 75

44. Appearance of FP after Flash Dewaxing . . . . . 77

45. Appearance of CP after Flash Dewaxing . . . . . 77

vi Figure Page

46. Inner Mold Wall of CP ...... 79

47. Outer Mold Wall of CP ...... I . 79 48. Interior of FP Mold after Flash Dewaxing 80

. . . .I 49. Interior of CP Mold after Flash Dewaxing 80 . . . .I 50. Interior of FP Mold ...... *.*.0.0.0 81

. . . I 51. Closeup of Circular Area of CP . . 81

. . . I 52. Rejoined Mold of FP ...... 83 . . . .I 53. Rejoined Mold of CP ...... 83 . . . . 54. Intact FP after Casting ...... 85

55. Intact CP after Casting ...... 85 ."" 56. Silicon Bronze Cast of FP after CompleteIMold Removal by Sandblasting ...... 0 . .0 . 86

57. Silicon Bronze Cast of CP after Complete IMold Removal by Sandblasting ...... 86

58. Detail of Cast Surface of FP ...... 4. 87

59. Completed Sculpture of CP ...... 88

vii

f jam, miqw , 1 1 1 , CHAPTER I

INTRODUCTION

Traditionally, only expendable materials have been used for patterns molded in ceramic shell. Wax and certain plas tics, completely removed from the mold during the ceramic shell dewaxing cycle, are the expendable materials most frequently used. The question as to whether or not it is an absolute necessity to use expendable materials led to this investigation of ceramic shell piece molds designed to acc omodate nonexpendable materials.

Originally developed by industry for precision casting, the ceramic shell mold has provided the sculptor with a lightweight and strong alternative to heavy sand and plaster molds. Basically, ceramic shell is composed of finely di vided particles of silica suspended in a liquid binder. Patterns periodically dipped into this solution, or slurry as it is commonly called, are completely enveloped with a thin, viscous film. While the patterns are still wet with slurry, refractory granules are applied, and coated patterns are allowed to dry. After repeating this process a specific number of times, an enclosing shell of material is built up, as seen in Figure 1. This, then, constitutes the ceramic shell molding procedure. Specific details of this process

1 2

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* 6 * 5 0 * 0 * 6

0* 0, 6 K 61 * 6 5 *0 ':~ i

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d Fig. 1--Steps in ceramic shell coating procedure: a. wax pattern; b. dipping wax pattern in ceramic shell slurry; c. sprinkling coated pattern with refractory granules; d. coating process completed. 3 have been dealt with extensively in foundry literature (1, pp. 123-5; 3, pp. 287-90; 5, pp. 161-2; 6, pp. 11-8-17; 8, pp. 122-5). Owing to this phenomenon of total pattern encapsulation, intricately constructed patterns having complex interior passages can be molded with ease (2, p. 126; 4, p. 208). These molds require less fuel to dewax; are easily repaired; take up less room for storage; and are much less cumbersome to handle.

Because the distinctive, layered wall ceramic shell forms around a pattern is relatively thin, major interest has focused on maintaining wall integrity of the mold before, during, and after pattern removal. The pattern, then, of necessity, must be expendable. Sophistication of wax removal techniques has resulted in the production of strong, crack free ceramic shell molds.

Fracture of the ceramic shell mold has always been con sidered as obviously detrimental, and studies in ways of avoiding it have consumed enormous amounts of time and eff ort. Quite possibly however, as this study will attempt to show, mold fracture can actually be an asset. By using controlled or guided fracturing, ceramic shell molds can be designed to break apart at specific points, thereby allowing an examination of the mold interior. Since the mold inter ior can be made easily accessible, the use of nonexpendable materials in ceramic shell molds becomes a distinct possi bility. Attention in this study is directed to the use of 4

ceramic shell piece mold configurations in sculpture.

Statement of the Problem

This investigation is concerned with ceramic shell

molding material, used in piece mold configurations for re

moval of nonexpendable pattern materials in sculpture. The

choice of using the ceramic shell process combined with non expendable materials gave rise to the following questions:

l. Will the residue of specific acrylic polymer paint

and aluminum be removed from the mold interior without dam aging the mold inner face?

2. Will ceramic shell piece molds reveal any signif

icant differences on dewaxing that are not demonstrated with whole ceramic shell molds?

3. Will temperature ranges used for dewaxing of whole ceramic shell molds be effective for dewaxing piece molds containing combinations of expendable and nonexpendable patterns?

4. Will possible reactions between identified acrylic polymer paint and the ceramic shell mold inner face affect the surface quality of the metal cast?

5. Will the ceramic shell piece mold serve as a functional instrument in metal casting?

Scope and Delimitations

This study is delimited to the use of ceramic shell in sculpture in the construction of piece molds designed for 5 removal of 1) flat patterns provided with one or more perpendicular projections, and one or more circular pro jections with a central conical depression, and 2) low relief, hollow cylindrical patterns. Each pattern type will be partially coated with Liquitex naphthol crimson acrylic polymer paint on outer surfaces, and will be com posed of 1) wax, or 2) wax combined with aluminum. No attempt will be made to judge the aesthetic merits of the bronze casts produced from such patterns.

Significance of the Study The ceramic shell process has been used for precision casting because of its ability to enclose complex patterns.

Attempts at forming colloidal silica bonded ceramic shell into a mold which is not enclosed, and indeed, is designed to be opened, have not been discussed in the literature. The desirability of having such a mold becomes quite sig nificant, however, when one considers the use of nonexpend able materials as patterns in ceramic shell molds. The nonexpendable materials, in an enclosed mold, could leave large amounts of residue inside after flash dewaxing. Acrylic polymer paint, for example, can greatly complicate complete evacuation of the mold. Penland, (7, p. 62) in his work with expanded plastic patterns, found that after flash dewaxing acrylic paint coated patterns, enough residue was left in the molds to make them "unsatisfactory for burn out 6 and casting." Flash dewaxing of acrylic paint appears to leave a residue of finely divided pigment which clings te naciously to the interior mold surfaces. Metal poured into a mold containing this debris will produce an undesirable cast which has irregular surfaces and may contain inclu sions. By developing a ceramic shell mold which can be opened, these deposits of residue can be thoroughly removed, leaving a clean mold surface. This type of mold offers the sculptor additional flexibility in surface decoration, and a wider choice of materials with which to work in the ceramic shell process. To summarize, the exclusive use of expendable mate rials, coupled with a concern for producing crack-free ceramic shell molds, has imposed a limiting effect on the ceramic shell process. This investigation explores the use of nonexpendable materials in ceramic shell piece molds, and the opening of these molds by controlled fracture of the mold wall. The remainder of this report is organized to provide a survey of related literature, the pilot study, the principal study, and summary, conclusions, and recom mendations for further study.

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Definition of Terms

Acrylic polymer paint.--A synthetic resin polymer emulsion containing pigment particles-;

Air vent.--A small opening or passage in a mold to facil itate escape of gases when the mold is poured;

Block mold.--A flask containing investment which surrounds a pattern or cavity;

Ceramic shell.--Silica suspended in a binding agent, which

when used with refractory granules, forms a thin-walled

mold around patterns;

Film lift.--Separation of the acrylic paint film from the wax ground. This separation is caused by entry of

liquid into the paint film/wax ground interspace; Flash.--A thin section of metal formed at the mold joint on a cast due to the cope and drag not matching properly.

Flash can also be caused by a crack in the mold wall; Flash dewaxing.--A sudden application of heat to a shell mold to remove the wax inside;

Gate.--That portion of the runner where molten metal enters the mold cavity; Gating system.--The complete assembly of sprues, runners, gates, and individual casting cavities in the mold;

Inner face.--That part of the mold wall containing impress

ions made by the pattern; 8

Investment.--A flowable mixture of a graded refractory filler, a binder and a liquid vehicle which when poured around a pattern conforms to its shape and subsequently

sets hard to form the investment mold; Microcrystalline wax.--A synthetic wax derived from petro

leum having a molecular weight of 490 to 800; Nichrome wire.--A stainless steel wire which will not melt at flash dewaxing temperatures; Parting line.--A line on a pattern or casting corresponding

to the separation between the cope and drag portions

of a sand mold; Pattern.--A duplicate of the object to be cast;

Pattern, expendable.--A material used in a mold which can be completely removed from the mold by melting, vapor ization, combustion, or solution;

Pattern, nonexpendable.--A material used in a mold which cannot be completely removed from the mold by melting, vaporization, combustion, or solution;

Pouring cup; basin.--The enlarged mouth of the sprue into which molten metal is poured; Piece mold.--A mold constructed in two or more segments, de

signed to be removed without damaging the pattern within; Precision casting.--A casting process in which a wax or thermoplastic pattern is used. The pattern is invested in a refractory slurry; after the mold is dry, the 9

pattern is melted or burned out of the mold cavity.

Precision casting is also known as the investment cast ing process or the lost wax process;

Refractory.--A material which is capable of resisting heat;

Rovn, woven.--Bundles of long untwisted strands of glass fibers woven together; Runner.--A channel connecting the sprue to the gate;

Shim, wax.--Thin sheet wax used as a wall to separate mold segments;

Silica flour.--A finely divided powder composed of ground silica;

Sprue.--A channel connecting the pouring cup and the runner to the gate and then to the cavity proper; Slu .--Silica suspended in a binding agent.

VOOORWOWN CHAPTER BIBLIOGRAPHY

1. Collins, L. W., Jr., "Ceramic Shell Mold Boosts Invest ment Casting Weight to 100 Pounds," Machinery, 67 (October, 1960), 123-125. 2. Deakin, R. C., "Checklist for Casting Processes," Machine Design, 46 (February, 1974), 126.

3. Dunlop, A., "Ceramic Shell Moulds," Metal Industry, 96 (April, 1960), 287-290. 4. Green-Spikesley, E., "Investment Casting; The Process and the Product," Metallurgia and Metal Forming, 42 (July, 1975), 208. 5. Herrmann, R. H., "Ceramic Shell Process to Expand Invest ment Casting Market," Foundry, 88 (August, 1960), 158, 161-162. 6. Nalco Chemical Company. Investment Casting, Chicago: Nalco Chemical Company, n.d.

7. Penland, L. C., "Expanded Plastics Used as Sculptural Patterns for Burn Out in Ceramic Shell Molds," unpub lished doctoral dissertation, Department of Art, North Texas State University, Denton, Texas, 1976.

8. "Prepare and Use Ceramic Investment Shell Molds," Ceramic Industry, 76 (April, 1961), 122-125.

10 CHAPTER II

A REVIEW OF RELATED LITERATURE

This review of related literature is an attempt to provide some sort of chronological order to the development of two distinct types of thin-walled molds, and the pro cesses associated with their manufacture. These thin-walled molds are the Croning Process shell mold, and the ceramic shell mold. A chronological listing of thin-walled mold development is not available in any one place throughout the literature. This account, therefore, is pieced together from numerous sources. The development of these molds, both in Europe and in the United States, was strongly tied in with the war effort of each country. Once the war ended, the industrial technology gained from the use of these molds was applied to peacetime production. For these reasons, in formation covering the mid-1930's through 1963 came solely from articles dealing with industrial foundry procedures. Sculptors, recognizing the advantages of thin-walled molds for the production of works of art, began publishing reports on these molds in 1964. Consequently, sources referred to for the 1964 to 1976 period were textbooks on sculpture and the National Sculpture Center Proceedings.

11 12

The Croning Mold

The origin of the first of the thin-walled molds to be discussed can be traced to Germany during World War II. In

Hamburg, during the years 1937 through 1947, Johannes Croning invented and developed a shell molding method known today as the Croning Process (3, p. 99). Historically, it is signif icant for it was the first process to utilize a relatively thin structure--or shell--for metal containment. Apparently, the usefulness of this process to the German war effort was considerable, for the patent application was given classified status. As early as 1944, the Croning Process was being used in the production of eight-centimeter hand grenades (29, p. 204).

Basically, the Croning Process shell mold is constructed in two halves with a mixture of sand and a plastic binding agent. An early account (23, p. 506) indicated that sand and binding agent were applied to split metal patterns heated to approximately 375 degrees Fahrenheit. The heated patterns caused the plastic binder to soften and conform to the pat tern's contour, while simultaneously binding the sand grains together. The metal patterns, with the sand and plastic mixture still clinging, were then cured in an oven at approx imately 580 degrees Fahrenheit for two or three minutes. After curing, ejector pins designed into the metal patterns were pressed to release the finished half molds from the pat terns. The half molds were later joined together for casting. 13

Exactly how Croning mold joining is accomplished is signif icant because of similarities to joining procedures used in the present study.

After the war, William McCullough, a member of the

United States Department of Commerce, interrogated Mr. Croning (15, p. 130). In his report, designated PB-81284,

McCullough indicated that "a[Croning]mold is formed by pasting two half molds together." For reasons of economy, foundries in the United States and in Britain began to ex plore more efficient joining methods. Roast, (24, p. 71) in his appraisal of the Croning Process, noted that bolts could be used to fasten half molds together, while Katz and

Donner (14, pp. 113-15) recommended the use of thermoplastic resin glue. During 1954, Brooks (4, p. 24) reported on a British method in which pneumatically controlled clamps were used to hold mold halves in alignment during casting. Bond ing tapes, U-type clips, rivets, and speed nuts have also been used successfully for repositioning mold halves (31, p. 99). Stapling half sections together has met with only limited success (14, p. 114).

The Croning Process eventually proved to be an impor tant technical advance for United States foundries, for by 1957, an estimated 225,000 tons of castings were produced by this method (28, p. 80). The Ceramic Shell Mold

The ceramic shell mold differs from the Croning Process mold in that 1) the ceramic shell mold wall is built up by multiple, thin layering, 2) no plastic binding agent is used, and 3) patterns are made of wax or plastic. The ce ramic shell mold had its origin in United States industry. Indications are that the ceramic shell mold evolved as a refinement of the lost wax process, although the literature is unclear on this point. Lost wax, known also as the in vestment mold process and the precision casting method, had been in use by dentists and jewelers in the 1930's (18, p.

5). By 1934, an extremely hard alloy composed of cobalt, chromium, and tungsten or molybdenum, and given the trade name Vitallium, was being cast by the investment mold pro cess by Austenal Laboratories, Inc., of New York. In 1937, it was being used with increasing regularity by dentists and physicians in the construction of dental prosthetics and orthopedic fixation devices (16, p. 55). With the advent of World War II, the need for more efficient ways of casting high refractory metals for use as bucket vanes became critical with research into turbosuper chargers in military aircraft. Because of high stress en countered during turbine rotation, bucket vanes were required to have smooth finish, balance, and precise dimension. Metal alloys for these parts, being unusually hard and corrosion resistant, were consequently very difficult to machine to

w4mram'. 15 exact specifications. Traditional sand mold casting of these high strength alloys was found to be unsuitable because of the great amount of time it took to machine away rough finishes, parting line flash, and poor alignment of the cast. By 1941, Austenal Laboratories was under government contract to produce bucket vanes by the investment mold process, using Vitallium as the alloy (16, p. 56). The

investment mold produced smooth casts, free of parting line flash coupled with exceptional dimensional accuracy, thereby greatly reducing machining time and cost.

Up until 1944, wax patterns of these bucket vanes were put directly into a flask and surrounded with liquid invest ment material. An interesting change in this procedure, which quite possibly signaled the beginning of layered mold

ing, came in two reports in 1944. Albin (1, p. 52) indicated that prior to total block investment, wax patterns were

"sprayed with what amounts to a facing sand." Merrick (16, p. 54) reported that "facing material is first applied

on the wax patterns and allowed to dry, depositing refractory material in fine crystalline form." This facing application was apparently not a standard procedure, for Glaser (10, pp. 52-4) and Herb (12, pp. 149-50) made no mention of it in their reports dealing with precision casting. Birdsall (2, p. 96) however, noted that in the production of bucket

vanes at Allis-Chalmers, a process was being used whereby wax patterns were dipped first into a silica flour solution 16

and then sprayed with fine sand. After drying, the sand

coated patterns were surrounded by a thick, liquid invest

ment material which later solidified, forming a block mold.

As early as 1949, reports began to appear in the liter ature describing the use of a layered ceramic shell mold,

thin-walled in design, without block mold backing. This

layered ceramic shell mold could be supported by dry sand for static casting, or reinforced for centrifugal casting

(19, p. 97; 6, p. 56). These reports dealt with the Mercast process, invented by E. F. Kohl. In this process, a mer cury pattern frozen at -76 degrees Fahrenheit, was period ically dipped into a ceramic slurry until coated sufficiently to form a shell of investment one-eighth to one-fourth inch thick. The shell-invested pattern was then brought to room temperature, and the mercury, upon liquifying, was poured from the mold.

In the middle 1950's, the Mercast process began to decline in use because of the expense and enormous weight of large patterns. One report indicated that the ceramic shell mold, while being used only in the Mercast process, could prove most useful if wax could be utilized as pattern ma terial (22, p. B-11). The major difficulty, it appears, was that the relatively low burn-out temperature of 200 degrees Fahrenheit being used caused immediate wax expansion and subsequent cracking of the mold (11, p. 110). In 1954, an attempt to circumvent this problem was described in a 17

London report on the Investment X process. Mold fracture

was eliminated by dissolving the wax pattern in the indus

trial solvent trichloroethylene, a procedure taking up to forty-five minutes to complete (30, p. 322).

By 1955, a two-piece version of the ceramic shell mold, again backed with solid investment, was being discussed

in industrial publications. In 1956, under the name Glas cast, it was perfected into a single mold requiring no additional supporting investment, and using wax as pattern

material (20, pp. 170-1; 21, pp. 218-19; 32, pp. 92-4). Available literature indicates that the problem of finding a short, reliable method of wax removal, was ultimately

solved with research into high temperature dewaxing of these Glascast molds (11, p. 110). This was highly significant

in that it removed the last remaining obstacle preventing

widespread use of the ceramic shell process. Acceptance of the ceramic shell as a tool useful to industry was

indicated by the unveiling of four new variations of the process: Mono-Shell, in 1957 (17, p. 138); the Z-Process,

in 1959 (26, p. 144); Nalco's Ceramic Shell, in 1959 (25, p. 148); and the Arwood Corporation's Ceramic Shell Process, in 1960 (5, pp. 102-4). Industry promoted refinements and modifications of the ceramic shell process to provide more efficient and economical methods of mass production. This, in turn, led to the incorporation of automatic 18

ceramic shell molding systems, which were available as early as 1960 (9, p. 288).

During 1964, the ceramic shell process was brought to the attention of hundreds of artists attending the Third

National Sculpture Casting Conference in Kansas. In this

conference, Schnier (27, pp. 1-8) presented a paper on the use of ceramic shell molds for the casting of sculpture.

Of particular interest to this study was his mention of the use of fiberglass mat for reinforcement of ceramic shell

molds. In the Fifth National Sculpture Conference of 1968, two subjects of interest to this study were brought up by Colson (7, p. 82). He discussed the use of a hacksaw

to cut open fired ceramic shell molds for internal exam ination, and noted that after internal repair of ceramic

shell molds, the mold wall fragment which had been removed

was put back in place and "reconnected to its location with [slurry-dippedj fiberglass cloth and stainless wire." In books written by Verhelst (33, p. 32) and Irving (13, p. 108), the use of glass fibers in ceramic shell mold rein forcement is also reported.

It is of particular interest to the present study that in the literature on ceramic shell molds, removal of nonex pendable patterns from ceramic shell molds has been of little concern. Mercury patterns appear to be the only exception,

as noted. This is due, possibly, to the overwhelming con centration on problems of expendable material, centered on 19

whole mold concepts. During the 1968 National Sculpture

Conference, Walsh (8, p. 89) did indicate that some plastics

left residue in the mold after dewaxing, but that it was re moved with solvents. Irving, (13, p. 108) in discussing materials that leave ash or residue after dewaxing, recom mended the use of a draft hole in the mold wall. He stated that, after dewaxing, "a blast of compressed air through

the mold cavity will effectively clear such residue . . " In summary, two kinds of thin-walled molds have been discussed in this chapter: the Croning Process mold, and the ceramic shell mold. The Croning Process mold, which originated in Germany, is similar to the ceramic shell piece mold in the present study in that it is thin-walled and is constructed of two half molds. These half molds must be joined together before metal pour. Various methods of joining the Croning molds were noted. The ceramic shell mold, originating in the United States, is also thin-walled and is constructed of the same material used for ceramic shell piece molds developed in the present study. Opening, cleaning, and rejoining of ceramic shell molds has had some precedence in the literature, and these instances were re ported. Ceramic shell piece molds, designed to break apart at specific points to expose nonexpendable residue inside the mold, and then rejoined for metal pour, have not been discussed in the literature.

*Lt- a.-v. W-01* n mracpnrwJwinUTtr, -F, -iFnr- I------CHAPTER BIBLIOGRAPHY

1. Albin, J., "Equipment and Material for Precision Cast ing," Iron 4g., 154 (November, 1944), 52.

2. Birdsall, G. W., "Casting Supercharger Buckets at Allis-Chalmers," Steel, 116 (January, 1945), 96. 3. "British Claim Patent Rights for Shell Molding," Iron Agj, 171 (January, 1953), 99. 4. Brooks, Dennis, "Clamping Shell Moulds," Canadian Metals, 17 (January, 1954), 24.

5. "Ceramic Shells Solve Problems on Heavy Complex Castings," Iron A9gj, 186 (July, 1960), 102-104.

6. Chase, Herbert, and Leslie T. Schakenbach, "New Pre cision Casting Process Provides Better Finish, Closer Tolerances," Materials and Methods, 29 (March, 1949),56.

7. Colson, Frank A., "Problems in Ceramic Shell," Proceed ings of the Fifth National Sculpture Conference, Lawrence, Kansas, University of Kansas, 1968.

8. Colson, Frank A., and Thomas Walsh, "Problems in Ceramic Shell-Question Session," Proceedings of the Fifth Nat ional Sculpture Conference, Lawrence, Kansas, Univer sity of Kansas, 1968.

9. Dunlop, Adam, "Ceramic Shell Moulds," Metal Indu , 96 (April, 1960), 288.

10. Glaser, J. W., "Refractory Molds for Precision Casting," Iron Age, 155 (February, 1945), 52-54.

II. Grant, Nicholas J., and Philip Manganaro, "Ceramic In vestment Shells," Tool Engineer, 38 (February, 1957), 110.

12. Herb, C.0., "Ford Produces High-Speed Steel Cutters by Precision Casting," Machinery, 51 (April, 1945), 149-150.

13. Irving, Donald J., Sculpture: Material and Process, New York, Van Nostrand Reinhold Company, 1970.

20 21

14. Katz, M. L., and S. B. Donner, "Improved Closing Methods Cut Shell Casting Costs," Iron Age, 173 (June, 1954), 113-115.

15. McCullough, William W., "Precision Molding Process Em ploys Resin Binder," Foundry, 76 (October, 1948), 130. 16. Merrick, Albert W., "Precision Casting of Turbosuper charger Buckets," Iron Agj, 153 (February, 1944), 54-56.

17. "Mono-Shell Process," American Machinist, 101 (July, 1957), 138.

18. Neiman, Robert, "Precision Castings Employing Dental Technique by Investment Molding Process," American Foundryman, 6 (September, 1944), 5

19. Neimeyer, William I., "Precision Casting with Frozen Mercury Patterns," Iron Ag, 163 (March, 1949), 97.

20. "New Glass-Powder-Mold Precision Casting Process Elim inates Knockout, Investment Materials," American Mach inist, 100 (June, 1956), 170-171. 21. "New Molding Process Uses Glass Shell Molds," Foundry, 84 (August, 1956), 218-219. 22. "One Hundred Years of Metalworking; Casting," Iron Age, 175 (June, 1955), B-11.

23. "Precision Moulding," Metal Industry, 71 (December, 1947), 506.

24. Roast, Harold J., "An Appraisal of the Shell Molding Pro cess," Metal Progress, 61 (April, 1952), 71.

25. Rueter, Raymond, "Ceramic Shell Mold Experiments," Metal Progress, 75 (May, 1959), 148.

26. Scheffer, Karl, "Fundamental Aspects of Ceramic Shells in Precision Casting," Metal Progress, 75 (May, 1959), 144.

27. Schnier, Jacques, "Ceramic Shell Molding for Sculpture Casting," Proceedings of the Third National Sculpture Casting Conference, Lawrence, Kansas, University of Kansas, 1964.

28. "Shell Molding; Ten Years of Progress," Foundry, 86 (April, 1958), 80. 22

29. Tindula, Roy W., "Current Status of the Shell Molding Process," Foundry, 80 (July, 1952), 204, 206.

30. Turnbull, J. S., "Development of Lost-Wax Process of Precision. Casting, 1949-1953," Proceedin , Institution of Mechanical Engineers 169 London, England, House of the Institution, 1955 31. "Two New Ways to Fasten Shell Mold Halves," Precision Metal Formin&, 12 (April, 1954), 99.

32. Unterweiser, P. M., "Single Glass Mold Smoothes Cast ing Wrinkles," Iron 4gj, 1?7 (May, 1956), 92-94.

33, Verhelst, Wilbert, Sculpture: Tools, Materials, and Techniues, Englewood Cliffs, New Jersey, Prentice Hall, Inc., 1973. CHAPTER III

PILOT STUDY

The review of related literature in art and in industry

yielded scant information regarding the possibility of using nonexpendable patterns in ceramic shell molds. Several

reasons for this can be considered: 1) nonexpendable mater ials do not burn free of the mold cavity, leaving debris

within the mold; 2) residues in the mold cavity contribute

to poor surface finish and inclusions in the metal cast; and

3) in an enclosed mold system like ceramic shell, there is

no ready way to completely remove this debris. This pilot study was undertaken to 1) attempt to under

stand the nature of the debris left in ceramic shell molds after exposure of nonexpendable materials to flash dewaxing,

and 2) to determine if cracking, previously considered

as undesirable in ceramic shell molds, could be used pos itively by controlling fracture along designated pathways.

With these considerations in mind, the following three pilot

study tests were conducted: 1) flash dewaxing of wax pat

terns coated with identified acrylic polymer paint; 2) piece mold separation and rejoining; and 3) modification of sprue and air vent systems on wax and aluminum patterns coated with identified acrylic polymer paint. In order to present

-1*11117 24 an overall view of the pilot study, general mold config urations used in each of the three pilot study tests are shown in Figure 2, p. 25. The wax used for all pattern construction in the pilot study was Victory Brown, a microcrystalline variety manu factured by the Petrolite Corporation. Acrylic polymer paints used for coating patterns were Hyplar, made by

M. Grumbacher Inc., and Liquitex, manufactured by Permanent

Pigments, Inc. Throughout the study, Hyplar paints will be designated (HY), while Liquitex paints will be denoted as (LQ). Each pattern in the pilot study was molded with ceramic shell slurry composed of Nalcoag colloidal silica, manufactured by the Nalco Chemical Company, and fine silica flour produced by Glassrock Products, Inc. Fine G-1 fused silica sand was used for the first granule application, while coarse G-2 was used after the second, third, and fourth slurry dips. Both grades were made by Glassrock.

To minimize the possibility of acrylic film lift, the pat terns were not washed with isopropyl alcohol before dipping.

Prewetting with Nalcoag colloidal silica was done, however, before the second, third, fourth, and fifth dips in slurry. Twenty-four hours drying time was permitted between each dip in slurry to insure complete drying. After the final slurry dip, a minimum of twenty-four hours drying time was allowed before further procedure. 25

s/tar rESr I: WHOLE MOLD

/t or rcsrJX.: P/ECE MOLD

IPzor rEsr .1ZZ: P/eCE MO4L

Fir. 2--General mold configurations used in pilot study 26

Pilot Study Test I: Flash Dewaxing of Wax Patterns Coated with Identified Acrylic Polymer Paint This test was intended to determine the effectiveness

of acrylic polymer paint as a pattern material. Combina

tions of seven acrylic polymer paints were applied to four

wax models. In order to vary sculptural design, the models were not alike:

1. Pilot I-1, a flat wax plate measuring ten inches by five and one-half inches by one-eighth inch, was brush coated with the acrylic polymer paints thalo blue (HY) and titanium white (LQ) to give rough texture;

2. Pilot 1-2, a flat wax plate measuring six inches by five inches by one-eighth inch, was brush coated with cad mium orange (LQ) and titanium white (LQ) in the same manner. The gating systems of Pilot I-1 and Pilot 1-2 were applied to one edge;

3. Pilot 1-3, a rectangular box, measured two and three-fourths inches by one and three-fourths inches on a side. A hole one inch in diameter was cut through the top. Thickness of the wax was approximately one-eighth inch. The outer surfaces were brush coated with cadmium yellow light (HY), manganese blue (HY), and titanium white (LQ) in order to give a rough texture. Gating was from the base; 4. Pilot 1-4 consisted of a one-eighth thick wax cyl inder eight inches tall and two and seven-eighths inches in diameter. It was brush coated on the outside with cerulean 27

blue (LQ) and napthol ITR crimson (LQ). Gating was from the base.

The acrylic paint applied to each pattern extended out

approximately one-half inch onto the wax runners leading to the pattern. At this point, the acrylic paint/wax junction

was sealed completely with liquid wax to prevent lift-off of the acrylic paint film. Each acrylic paint coated pattern was dipped into ceramic shell slurry five times. The first dip was followed by a sprinkled application of fine fused silica granules. The second, third, and fourth dips were followed with coarse fused silica, and the fifth dip without granule application to seal loose sand grains. Twenty-four hours drying time followed each dip and granule application. Three to five slits in each mold were made with a bandsaw blade to expose small pinpoints of the pattern. This was done to help avoid mold cracking due to pattern expansion (2, p. 11-14).

Flash Dewaxing and Casting

The four molded patterns were wired to a stainless steel rack. They were then inserted into a plate steel cylindrical brick-lined furnace, measuring forty-five inches high with a diameter of thirty-six inches. This bottom loading furnace, used by Penland (5, pp. 54-5) in his work with ceramic shell molds, was fueled with natural gas through a single three inch line with air booster assist from a squirrel cage type 28

blower. Temperature at time of insertion, taken with a

T-2 Paragon pyrometer, was 1,700 degrees Fahrenheit. After a brief drop to 1,500 degrees, caused by lowering the bottom

door, the temperature stabilized at 1,600 degrees Fahrenheit.

After five minutes, all wax stopped dripping out through the central hole in the door bottom. Temperature was gradually

reduced over a thirty minute period to 1,050 degrees and then gas and air assist were turned off. The door was lowered and the molds removed.

Previously cut slits in Pilot I-1, Pilot 1-2, and Pilot 1-4 were sealed with slurry thickened slightly with addi tional silica flour, and no attempt was made to remove any residue remaining inside. Fine silica sand was poured

through the pouring cup into Pilot 1-3 and the mold shaken vigorously to loosen any residue. The sand was poured out, accompanied by numerous small particles of a packed talc

consistency. This procedure was followed three times, and after final sand removal, the mold was flushed with a stream of compressed air. No further particles fell from the mold when inverted, indicating that no free particles remained inside. The mold slits were then sealed as in Pilot I-1,

Pilot 1-2, and Pilot I-4, above. After sealed areas had dried, the molds were preheated at 1,300 degrees Fahrenheit for one hour in the dewaxing furnace described previously.

Silicon bronze, at a temperature of 2,075 degrees Fahrenheit 29

was then poured into each mold. Molds were supported in dry

sand for casting. Figures 3 and 4, p. 30, show two views of a fragment of the inner face of the mold wall of Pilot 1-1 after casting. In Figure 3, the fragment is covered with residue, while in Figure 4, the residue has been removed

with a stiff brush. Figure 5, p. 31, is a comparison of the metal surfaces of Pilot 1-2, Pilot 1-3, and Pilot 1-4 after sandblasting.

Results of Pilot Study Test I I. Molds of Pilots I-1, I-2, 1-3, and 1-4 did not show any evidence of cracking, indicating that acrylic polymer

paint coatings on wax patterns did not significantly add to the normal expansion characteristics of microcrystalline wax. 2. Silicon bronze casts of molds of Pilots I-1, I-2, and 1-4 exhibited extremely poor reproduction of the original

brushed texture, indicating that residue inside each mold

was excessive. A lack of residue inclusions in the metal

further indicated that the residue was probably adhering to

the inner face of the mold and was not breaking free into the cavity proper.

3. Examination of the bronze cast made from Pilot 1-3, which had been purged with fine sand and compressed air, ex hibited fair reproduction of the original pattern. This in dicated that if mold residue could be removed completely, a cast similar to the pattern could possibly be produced. 30

/ 'I vW ami~~f.444

~ A 414 Ali, 0

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70 it 10p.

Fig. 3--Mold fragment of Pilot I-1. Res- idue covers the surface.

'.5

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Fig. 4--Mold fragment of Pilot I-1. Res- idue has been removed. 31

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4 32

4. Casts made from Pilots 1-1, 1-2, 1-3, and 1-4, in dicated that the whole mold technique used in this pilot study test was not an effective method. While some residue could be evacuated, most remained within the mold, thereby producing casts with defective surfaces. To summarize, after flash dewaxing of molds in Pilot

Study Test I, acrylic coatings on wax patterns did not appear to contribute to mold cracking, but did leave too much res idue. Partial removal of this residue resulted in a slightly

better metal cast, but complete residue removal appeared

impossible in whole ceramic shell molds. In order to de termine whether ceramic shell molds could be opened, cleaned, and rejoined, Pilot Study Test II was initiated.

Pilot Study Test II: Piece Mold Separation and Rejoining Preparation for Dewaxing

After examining the results of Pilot Study Test I, this

test was conducted to determine if mold segments could be

rejoined, as Colson (1, p. 82) had indicated, and to test

the performance of a ceramic shell mold designed to be opened, cleaned, and resealed. Three samples were tested; Pilot II-1, Pilot 11-2, and Pilot 11-3. 1. Pilot II-1 consisted of a one-eighth inch thick

sheet of wax measuring five and one-half inches by three and three-eighths inches. The wax was bent to produce a slight curve along the long axis, and gating was from one side. 33

The wax was brush coated on one side with hansa orange (HY), cadmium red medium (HY), and titanium white (LQ), in the same manner as in Pilot Study Test I. 2. Pilot 11-2 consisted of a one-fourth inch thick wax plate measuring eight inches by twelve inches. This plate was then centered on a larger sheet of wax measuring ten inches by fourteen inches and one-eighth inch thick. The two wax sections were wax welded together along the margins of the upper, thicker plate. The purpose of the larger but thinner sheet was to function as a wax shim line during later mold buildup. Pouring cup, sprue, runners and air vents were applied for vertical pouring. The completed wax pattern is shown in Figure 6, p. 34. Nine flattened plastic drinking straws, approximately one inch in length, were placed in a parallel arrangement in the center of the thick plate. Napthol ITR crimson (LQ), was then brushed onto this surface forming horizontal bands of texture which divided the plate into approximate thirds. The upper and lower thirds were rough in texture, while the middle third, containing the plastic straws, was relatively smooth. The paint was continued down each side of the plate and extended about one fourth inch onto the thinner backing wax sheet, and onto the air vents and runners. This acrylic paint/wax junction was sealed with liquid wax as described in Pilot Study Test I. 3. Pilot 11-3, a one-fourth inch thick plate of wax, 34

Fig. 6--Completed wax pattern of Pilot 11-2 35

measured five and one-fourth inches by five and one-fourth

inches. As in Pilot 11-2, this wax plate was centered and welded onto a larger, thinner sheet of wax measuring seven

and one-fourth inches by seven and one-fourth inches. Pour

ing cup, sprue, runners, and air vents were applied for ver tical pouring. Flattened plastic drinking straws one and one-half inches long, were then placed in a fence-like pro gression horizontally across the middle third of the plate. Ends of the straws were sealed with wax. The upper third

of the wax plate was scraped with a file-like instrument to produce parallel, vertical rows of texture. The lower third was partially textured.

A mixture of manganese blue (HY) and titanium white (LQ) was then brushed onto the surface. The paint on the upper

third was applied in a thin layer, coloring the texture un derneath, and brought downward to coat the upper half of

the straw fence. The lower half of the fence was left un painted. Paint was applied to the lower third in very thick, rough portions, forming numerous undercuts., As in previous

samples, the sides of the plate were painted, with the paint film extending one-fourth inch onto the thin backing plate, the runners, and air vents. Liquid wax seal was applied at these junctions. The coated pattern is shown in Figure 7, p. 36.

Pilots 11-1, 11-2, and 11-3 were molded with ceramic shell, and slits were cut in Pilot II-1 in the manner 36

hFWrr 't~r

Fig. 7--Pilot 11-3 pattern after straw and paint application. 37 described in Pilot Study Test I. Pilots 11-2 and 11-3, however, underwent additional procedures normally not associated with the ceramic shell process. After completely drying for twenty-four hours, the outer edge of the mold covering the thinner backing wax sheet of Pilots 11-2 and 11-3 was carefully crushed with pliers, revealing the wax inside. The edge of the mold directly behind the runners was so closely integrated with the runner system, that it was cut with a bandsaw blade. Pilot 11-2, before and after crushing'and cutting, is pictured in Figures 8 and 9, p. 38. Nichrome wire was wrapped around Pilots 11-2 and 11-3, and each was secured to the stainless steel rack, pouring cup down, in preparation for flash dewaxing.

Flash Dewaxing and Casting

Pilots 11-1, 11-2, and 11-3 were placed in the dewaxing furnace, previously described in Pilot Study Test I, main tained at 1,700 degrees Fahrenheit. After dropping to 1,550 degrees, the temperature stabilized at 1,650 degrees Fahren heit. Within five minutes, wax was no longer dripping from the door escape hole, and temperature was reduced to 1,400 degrees Fahrenheit. Temperature was slowly reduced over a twenty minute span until 1,100 degrees Fahrenheit was reached. Gas and air assist were then shut down, the door lowered, and the molds withdrawn.

After Pilot II-1 had reached ambient temperature, fine silica sand was poured in through the cup. The mold was 38

Fig. 8--Pilot II-2 a ter completion of molding

ANO f

FiL:. 9--Pilot I1-2 after crushing of mold 39

shaken and inverted to remove the sand and accompanying

particles, and compressed air was injected as in Pilot 1-3 of Pilot Study Test I. Thickened slurry was applied to close the slits. After the slit closures had dried, the lower corners of Pilot II-1 were removed with a bandsaw blade.

The two triangular corner pieces each measured approximately two inches by two inches by three inches. Ceramic shell

slurry was applied to the exposed cut surfaces of both corner pieces and the mold proper, and each corner was positioned

back into place on the mold. Additional slurry, thickened with silica flour, was applied to seal the joining areas.

Mat fiberglass, dipped in slurry, was then spread over these areas for reinforcement. After twenty-four hours drying

time, the rejoined mold was dipped in slurry to seal the fiberglass strands. Care was taken not to allow slurry into the pouring cup.

After drying for twenty-four hours, the mold was pre heated to 1,300 degrees Fahrenheit for one hour in the furnace previously described. It was removed, packed in dry sand, and cast with silicon bronze at a temperature of 2,075 degrees Fahrenheit. Figure 10, p. 40, shows a closeup of the metal cast picturing one rejoined area.

After examining the cast of Pilot II-1, Pilots 11-2 and 11-3 were prepared. Each mold, previously wired shut, was opened. Residue was removed with a stiff brush. After residue removal, the individual mold halves, looking much 40

Fig. 10--Metal cast of Pilot II-i. This closeup view shows one re joined area.

I I - like flat plates, were joined together and aligned. Sealing

was accomplished by applying thickened slurry over the entire outer edges previously crushed and cut. This seal was ap plied to cover the exposed outer edges, and to overlap, to a small extent, onto the front and back sections of the aligned molds, forming a wrap-around seal. After drying for twenty-four hours, two layers of mat fiberglass, dipped in slurry, were wrapped around the outer edges of Pilot 11-2 for reinforcement.

The pouring cup of Pilot 11-3 was wrapped with slurry

dipped mat fiberglass, while the rest of the mold was com pletely enveloped in woven fiberglass roving dipped in slurry. Additional reinforcement of mat fiberglass was applied over the roving layer along the edges and bottom corners.

Pilots 11-2 and 11-3 were preheated in the furnace described, for one hour at 1,300 degrees Fahrenheit, then removed and packed in dry sand. Silicon bronze, at 2,100 degrees, was poured into each mold. Pilots 11-2 and 11-3, after mold removal and sandblasting, are depicted in Figures 11 and 12, p. 42.

Results of Pilot Study Test II

1. The mold of Pilot II-I, treated with sand and com pressed air as was Pilot 1-3, in Pilot Study Test I, produced a metal cast with fair fidelity to the detail of the orig inal, indicating that extensive residue within the mold 42

Fig. 11--Metal cast of Pilot 11-2. Large mass of protruding metal is at lower right.

'-4Lf

* ; -4WT4

IFA

Fig. 12--Intact meta L cast of Pilot 11-3. Parting line flash is alo ig periphery. 43

had been loosened somewhat.

2. The cast of Pilot II-1 indicated that rejoining of previously separated mold segments could be accomplished.

Molten metal did not break the bond formed at the junction of said segments.

3. Temperature ranges used in pattern removal were those normally used in flash dewaxing of whole ceramic shell molds. An absence of mold cracking, excessive carbon de

posits, or mold fragmentation in Pilots 11-2 and 11-3, indicated that these temperatures were effective for flash dewaxing of acrylic polymer paint coated wax patterns de

signed in these piece mold configurations. Figure 13, p. 44, depicts the condition of Pilot 11-2 after dewaxing.

4. Pilots 11-2 and 11-3, prepared for flash dewaxing after the casting of Pilot II-1, indicated that the wax shim

integrated into the wax pattern, effectively separated the mold into front and back sections, as seen in Figure 14, p. 44.

5. Debris left by napthol ITR crimson (LQ) inside the mold of Pilot 11-2 was excessive, but easily removed with

brushing. This indicated that it could perform well as a

surface coating on wax. This residue is pictured in Figure 15, p. 45.

6. Debris left by the mixture of manganese blue (HY) and titanium white (LQ) inside the mold of Pilot 11-3 was excessive. The vast majority was removed by brushing, but 44

Fig. 13--Mold of Pilot 11-2 after dewaxin-. Lijht carbon deposits can be seen at left.

Fig. 14--Separation of ceramic shell mold. Front half of the mold is at left. 45

Fig. 15--Mold wall of Pilot 11-2. Residue covers the surface.

Fig. 16--Mold wall of Pilot 11-2. Residue has been removed. 46

"mmlow 0-41.0, d.-Ap, fill, a

*a- PVM 0 0 4r

,_4

Fig. 17--Mold wall of Pilot 11-3. Residue covers the surface.

. *V_.j

Fig. 13--Mold wall of Pilot 11-3. Residue has been removed. 47 some residue still adhered to the mold inner face and could not be removed. This indicated that these two paints, in combination, did not perform well as a surface coating on wax. Debris inside Pilot 11-3 can be seen in Figure 17, p.46.

7. The inner face of the mold of Pilot 11-2, after cleaning, was intact and in good condition except for a small area measuring three-eighths inch in diameter. The etiology of this erosion was not determined. The cleaned inner face is pictured in Figure 16, p. 45. 8. The inner face of the mold of Pilot 11-3 was chipped in several places. These defects occurred on the lower third of the mold in the area where very thick paint had been applied. No defects of this kind were in evidence in either the upper or middle thirds, indicating the pos sibility that the paint thickness may have been a contrib uting factor. The lower third had also taken on a distinct red-violet color, penetrating well into the surface. Pilot

11-3, after cleaning, is shown in the closeup view in Figure 18, p. 46.

9. Casting of Pilot 11-2 broke the piece mold at the lower edge and progressed along the bottom and one vertical edge. A refill of metal was attempted, but this fractured the mold front and back. An examination of this cast in dicated that reinforcement along the edges was not strong enough to contain the metal. Good reproduction of the original pattern was seen on the lower third of the cast. 48

The complete cast and a closeup of the surface can be seen in Figures 19 and 20, p. 49.

10. During the casting of Pilot 11-3, the mold remained

intact. The cast was complete and in good condition. Ex

pected metal flash along the edges was present. The mold, remaining intact, indicated that reinforcement along the edges was sufficient to contain metal. The mold, immediately after casting, is pictured in Figure 21, p. 50. Reproduction of the original pattern was good, with the exception of those areas overlying chipped places in the mold. Figures 22 and 23, p. 51, show closeup views of the cast surface.

To summarize the results of Pilot Study Test II, it was found that 1) mold segments could be cut apart and rejoined for metal pour; 2) wax shims could be used to provide sep aration of mold halves; 3) temperature ranges for flash dewaxing of wax patterns in whole ceramic shell molds, were

effective for ceramic shell piece molds as well; 4) napthol ITR crimson (LQ) was effective for coating wax patterns, while other acrylic paints tested were not; 5) heavier fiberglass reinforcement was necessary for ceramic shell piece molds designed to contain larger amounts of metal; 6) changes in design of ceramic shell piece molds were warranted to insure protection of the mold during metal pour. In order to improve ceramic shell piece mold design for use with wax patterns containing acrylic polymer coatings and other nonexpendable material, Pilot Study Test III was begun. 49

Fig. 19--Cast of Pilot 11-2. Metal break throu-h is seen at lower left.

7VP

Fig. 20--Cast of Pilot 11-2. Closeup of lower right corner of complete cast. 50

do 4 - ; L

. -t

Fig. 21--Mold of Pilot I1-3 after casting 51

Fig. 22--Cast of Pilot II-3. Closeup of upper and middleII thirds of cast.

Fig. 23--Cast of Pilot 11-3. Closeup of lower and middle thirds of cast. 52

Pilot Study Test III: Modification of Sprue and Air Vent Systems on Wax and Aluminum Patterns Coated with Identified Acrylic Polymer Paint

Preparation for Dewig The purpose of this test was twofold: 1) to determine

if molds, made from patterns gated for horizontal pour, would perform more favorably during casting, and 2) to determine if aluminum could be used jointly with selected

acrylic polymer paint as pattern material in ceramic shell piece molds. The first part of the test, as stated above,

was suggested by the mold failure of Pilot 11-2, which broke

apart during casting. In Figure 24, p. 53, the diagram of Pilot 11-2 illustrates how metal entering the mold from

above can strike the interspace over the sealed mold border.

Weight of molten metal in this area could possibly act much like a wedge, forcing the two halves of the mold apart.

This diagram of Pilot 11-2 can be compared to the one re presenting Pilots III-1 and 111-2. Here, the diagram shows how this interspace area might be better protected. Weight

of the metal is concentrated on one side of the mold, rather than on the bonded joint.

Figure 25, p. 54, illustrates how patterns were changed for horizontal gating. In this figure, the design of Pilot 11-2 is compared to the design for Pilots III-1 and 111-2.

Basic design changes made included 1) bending of the sprues and runners approximately ninety degrees to allow for flat 53

MEALIi. E4N7Ry

II-2

A1ErA AE Ar& Y

amold wall

seal fiberglass

Fig. 24--Diagram of the position of the sealed mold border during vertical and horizontal pour. 54

C &n

pouring cup runner bsprue eair vent departure c air ventfrom runner

Fig. 25--Pattern design changes. Pattern of Pilot 11-2 is compared to patterns of Pilots III-1 and 111-2. 55

or horizontal pouring, and 2) changing air vent entry.

Sprues and runners were bent to allow the impression side

of the mold to face downward during metal pour. Slag, col

lecting in the mold during pouring, would therefore have a tendency to float upward toward the back side of the mold.

Here, slag inclusions would be of little consequence (5, p. 278). Bending of the wax sprue and runners of each mold was gradual. This produced a rounded curve of approximately

ninety degrees, rather than a sharp, cornered turn. This

rounding was designed to minimize metal turbulence (4, p. 178). Aside from these changes in design, the patterns

of Pilots III-1 and 111-2 were constructed in the same

manner as those in Pilot Study Test II.

During the wax building stage, Pilot III-1 was fitted

with three aluminum parts. Two of these were circular pro jections with central conical depressions, while the third

was shaped as a conical projection. Once the aluminum had been fitted into place and the wax modeling completed, the pattern was brush coated with napthol ITR crimson (LQ) in the manner previously described in Pilot Study Test II. Pilot III-1, with coating applied, is seen in Figure 26, p. 56.

Pilot 111-2 was equipped with one aluminum fitting similar to those of Pilot III-1. After modeling was com pleted, the pattern was brush coated with naphthol crimson (LQ). Pilots III-1 and 111-2 were molded with ceramic 56

Fir. 26--Pilot Il-i ready for molding 57

shell, and shim borders crushed and cut, in the manner

described for Pilots 11-2 and 11-3 in Pilot Study Test II. One additional procedure was carried out: nichrome wire was pushed into the exposed wax shim border. This was done in

four or five places along the border to keep the mold halves

slightly separated for residue egress during flash dewaxing.

Each piece mold was wrapped with nichrome wire, and secured to the stainless steel rack.

Flash Dewaxing and Casting Pilots III-1 and 111-2 were placed in the dewaxing

furnace maintained at 1,650 degrees Fahrenheit. After a

temporary reduction to 1,475 degrees, due to lowering the door, temperature stabilized at 1,600 degrees Fahrenheit.

After wax ceased dripping through the escape hole, tem

perature was slowly reduced over a fifteen minute period to 925 degrees Fahrenheit. Gas and air assist were turned off, the door lowered, and the molds removed.

Each mold was opened, cleaned, resealed, and dried, as described in Pilot Study Test II. They were preheated

in the dewaxing furnace at 1,300 degrees Fahrenheit for one hour, then removed and packed in dry sand. Silicon bronze, heated to 2,100 degrees Fahrenheit, was poured into each mold. Figures 27 and 28, p. 58, illustrate the position of each mold during metal pour. Casts of Pilots III-I and 111-2 are shown in Figures 29 and 30, p. 59, after mold removal and sandblasting. Smooth surfaces of the casts were polished. 52

Fig. 27--Mold of Pilot 117-1 after cast ing. Mold is completely intact.

r C

Fig. 28--Mold of Pilot 11-2 after cast ing. Mold is completely intact. 59

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4r-4r $.. ~

Fig. 29--Cast of Pilot III-1. Discs have been polished for contrast.

or 'A. 1~) Fig. 30--Cast of Pilot 111-2. Disc and the five bars have been polished for contrast. 60

Results of Pilot Study Test III

1. Pilots III-1 and 111-2, prepared with wax shims,

underwent mold separation without incident during flash de waxing.

2. An absence of mold cracking, carbon deposits, or mold fragmentation in Pilots III-1 and 111-2 indicated that temperatures used in flash dewaxing, were effective for these wax and aluminum patterns coated with identified acrylic polymer paints.

3. Debris left by napthol ITR crimson (LQ) in Pilot III-1 was excessive, but easily removed with a brush. This paint performed well as a surface coating in this test.

4. In Pilot 111-2, debris left by naphthol crimson

(LQ) was similar in appearance to that of napthol ITR crim son (LQ). It too, was easily removed by brush, and per formed well as a surface coating.

5. Aluminum affixed to Pilots III-1 and 111-2 melted

during flash dewaxing and released from the mold inner face without difficulty. The acrylic polymer paint coating probably eased this release.

6. Nichrome wires pushed into the shim line effectively kept mold halves separated during flash dewaxing.

7. The mold inner face of Pilots III-1 and 111-2 was in good condition after cleaning.

8. During the casting of Pilots III-1 and 111-2 both molds remained intact, and no unusual incidents occurred. 61

This indicated that mold reinforcement was sufficient to contain metal, and that design changes to protect sealed areas offered possible advantages.

9. Metal casts of Pilots III-1 and 111-2 were in good

condition and exhibited very good reproduction of the original pattern. This indicated that mold design changes functioned as planned.

To summarize Pilot Study Test III, it was found that

1) aluminum, coated with napthol ITR crimson (LQ) or na phthol crimson (LQ) could be used as pattern material;

2) redesigned ceramic shell piece molds worked effectively;

3) increased fiberglass reinforcement around the mold kept

the mold intact during metal pour.

Synthesis of Major Findings of the Pilot Study

1. Napthol ITR crimson (LQ) and naphthol crimson (LQ) can be used as wax pattern coatings in ceramic shell.

2. Aluminum can be used as pattern material. 3. Flash dewaxing temperatures used for whole ceramic

shell molds can be used to dewax ceramic shell piece molds. 4. Ceramic shell molds, divided and then rejoined with sufficient reinforcement, can contain molten metal. 5. Wax shim lines can be used to accomplish ceramic shell mold separation along specified routes. 6. Ceramic shell piece molds can serve as functional instruments in metal casting. CHAPTER BIBLIOGRAPHY

1. Colson, Frank A., "Problems in Ceramic Shell," ings Proceed of the Fifth National Sculpture Conference, Lawrence, Kansas, University of Kansas, 1968 2. Nalco Chemical Company. Investment Casting, Chicago: Nalco Chemical Company, n.d.

3. Penland, L. C., "Expanded Plastics as Sculptural Patterns for Burn Out in Ceramic Shell Molds," doctoral unpublished dissertation, Department of Art, North Texas State University, Denton, Texas, 1976. 4. Sylvia, J. G., Cast Metals Technology, chusetts, Reading, Massa Addison-Wesley Publishing Company, 1972. 5. Taylor, H. F., M. C. Flemings, and J. Wulff, Foun Engineering, New York, John Wiley and Sons, Inc., 1959.

wg,-Wwpa*mm "'Woll, - - Wo", M CHAPTER IV

PROCEDURAL TECHNIQUES FOR CERAMIC SHELL PIECE MOLDS

Findings of the pilot study indicated that ceramic shell piece molds can be used to accomodate nonexpendable materials. Using information gained in the pilot study, the principal experiment was initiated to establish a pro cedural technique for utilization of the ceramic shell piece mold in sculpture. Two pattern types were put into production and photographed in each stage of the above procedure. These black and white photographs of each pattern type are arranged sequentially in this segment of the study.

Pattern Type Selection Two pattern types were selected for the principal ex periment. Varying significantly in shape, size, and weight, the pattern types are 1) the flat pattern type, as seen in Figure 33, p. 68, and 2) the hollow cylindrical pattern type as seen in Figure 34, p. 68. The flat pattern type was selected to determine if the results obtained on a similar pattern type in the pilot study were replicable. The cyl indrical pattern, however, was chosen to test the strength and performance of the ceramic shell piece mold when required

63 64

to contain greater amounts of metal than had been used pre viously. Weight of the metal casts from the molds in this study can provide the sculptor with a better understanding of the pattern weight range of the ceramic shell piece mold.

Sources of Data Sources of data of the principal experiment include the following: 1. Photographic documentation of each pattern, mold, and cast;

2. Written observation of the condition of each pattern, mold, and cast; 3. Data reports of time and temperature ranges used during flash dewaxing of each mold; 4. Data reports of time and temperature ranges used during preheat of each mold; 5. Data report of temperature of silicon bronze immed iately prior to pouring of each mold.

Procedure To clarify the procedural technique used, it can be divided into the following five stages: 1. Pattern construction; 2. Formation of the ceramic shell piece mold; 3. Dewaxing and separation of the ceramic shell piece mold into halves; 65

4. Rejoining of ceramic shell piece mold halves;

5. Casting of ceramic shell piece molds.

Pattern Construction

The flat pattern, hereafter referred to as FP, is seen in Figure 31, p. 66. In this first stage of development,

the pattern is composed of Victory Brown wax with one

attached aluminum insert. The incorporation of a wax shim

line into the pattern is of major importance in pattern con

struction. This wax shim line, seen in the photograph, will serve to separate the mold into front and back halves during

a later stage. Essentially, it is a thin sheet of wax, one

eighth inch thick, which has been wax welded to the back of a one-fourth inch thick wax plate. Styrofoam is used to

construct the pouring cup, while plastic drinking straws make up the air vent system. The pattern, with pouring cup facing downward, will remain in this position throughout much of the procedure.

The hollow cylindrical pattern, hereafter denoted as

CP, is seen in the first stage of production in Figure 32, p. 66. Wax used for preparation of the pattern is also Victory Brown. As in FP, wax shim lines are of major im portance in pattern construction. Placement of an upper wax shim line can be seen along the top edge of the pattern in this overhead view. It appears much like a fence and is approximately one-eighth inch thick. A lower wax shim line 66

b a I a

- - .' 1-s s .ht

-9* *( 9

-' ' - OP , -;*r

Fig. 31--End view of wax pattern of FP: a. wax shim line; b. aluminum insert.

Fig. 32--Top view of wax pattern of CP: a. wax shim line. 67

(not pictured in this view) is also in place along the bottom of the pattern. The wax shim lines will serve to separate the inner mold wall from the outer mold wall in later stages of the procedure.

The application of acrylic polymer paint to the wax pattern is also a part of pattern construction. In Figure

33, p. 68, naphthol crimson (LQ) paint has been applied to FP. This overhead view shows the pigment coating completely covering the front of the thicker wax plate. The paint coating extends out for a short distance onto the wax shim line, runners, and air vents. Liquid wax is applied with a brush to seal the paint/wax boundaries on the shim line, runners, and air vents. This is done to keep ceramic shell slurry from seeping under the paint film. In Figure 34, p. 68, naphthol crimson (LQ) paint has been applied to CP. This particular arrangement of pigment is in the shape of a sharply defined circle. A similar design, not pictured, is on the back of the wax pattern. Sealing of the paint/wax border, as seen in Figure 35, p. 69, was done with a solder ing iron. This keeps wax buildup to a minimum and allows the acrylic paint to retain its sharp, circular border. After letting the acrylic paint coating on FP and CP dry for several days, these patterns were complete and ready to undergo the second stage of the procedure. 68

- q

{, \

C-) Litii P1

*rH 69

Fig. 35--Closeup of paint/wax seal of CP. The border of acrylic paint, which can be seen at a, re mains sharply defined. 70

Formation of the Ceramic Shell Piece Mold

To begin this second stage of the procedure, FP and CP were molded in ceramic shell slurry composed of Nalcoag colloidal silica, manufactured by the Nalco Chemical Com pany, and fine silica flour produced by Glassrock Products,

Inc. Fine G-1 fused silica sand was used for the first granule application, while coarse G-2 was used after the second, third, and fourth slurry dips. Both grades were made by Glassrock. To minimize the possibility of acrylic paint film lift, the patterns were not washed with isopropyl alcohol before dipping. Prewetting with Nalcoag colloidal silica was done, however, before the second, third, fourth, and fifth dips in slurry. Twenty-four hours drying time was permitted between each dip in slurry. With the ex ception of omitting the isopropyl alcohol wash, this ce ramic shell molding procedure is identical to ceramic shell procedures used for expendable patterns. Figures 36 and 37, p. 71, show FP and CP after ceramic shell molding has been completed. The coated patterns are now entirely enclosed within the mold. Because of its large size, wax expansion slits (not pictured) were cut into the mold wall of CP. After drying for twenty-four hours, piece molding is begun. First, the edge of the ceramic shell mold which covers the wax shim lines is gently crushed with pliers. This exposes the wax inside, which is seen in Figure 38, p. 72. 71

pCr-) q

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Fig. 38--Crushed edge of mold of FP. Wax shim line is exposed.

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Fig. 39--Closeup of mold of CP. Mold was cut at a. 73

Care is taken to remove as little mold material as pos sible. In areas where the wax shim line is in close prox imity to the runner channels, the mold is cut rather than crushed. Figure 39, p. 72, and Figure 40, p. 74, show mold areas that have been cut. The lower wax shim line of CP, which was mentioned earlier, is seen in Figure 41, p.

74, after mold crushing. Once the edges of all wax shim lines have been ex posed, nichrome wires are pushed into the wax shim. These wire segments, pictured in Figures 42 and 43, p. 75, serve to keep the mold walls slightly separated during later de waxing. Separation facilitates residue egress. Four or five wires pushed into the wax shim are sufficient to accom plish this slight separation. After nichrome wires are in place, the complete mold is loosely wrapped with several long pieces of nichrome wire. This keeps the mold halves together during later dewaxing. At this point, the molds are ready for the next stage in the procedure.

Dewaxing and Separation of the Ceramic Shell Piece Mold into Halves Because of their size, FP and CP were subjected to dewaxing at different times. In order to effectively des cribe the dewaxing of each, they will be dealt with in dividually, beginning with FP.

FP was first wired to a stainless steel rack for han dling. The dewaxing furnace, described previously, was 74

a 4i; I A'

-1 --- W- _a.

Fig. 40--Back side of FP mold. Cut area is at a.

* :-..- a 1 4

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Fig. 41--Crushed mold of CP. Lower wax shim line is exposed. 75

jP I 4

Fig. 42--Edge of crushed mold border of FP. Nichrome wire is in place.

soft,

Fin. 43--Exposed lower wax shim line of CP. Nichrome wires are in place. 76 maintained at 1,700 degrees Fahrenheit for mold entry. Open ing the door for mold entry caused a temporary drop in tem perature to 1,450 degrees. Temperature soon stabilized at

1,500 degrees Fahrenheit. All traces of dripping wax at the door bottom ceased in three minutes, and in five minutes, the temperature was slowly lowered. At 1,200 degrees Fah renheit, the mold had been in the furnace for a total of twenty minutes. At this point, gas and air assist were shut down and the mold was removed. As seen in Figure 44, p. 77, light carbon deposits were present on one end of the mold, but the rest of the mold was white in appearance. The mold halves were not damaged, and nichrome wires were still present along the shim lines. CP was later wired to the same stainless rack and placed into the dewaxing furnace which was maintained at

1,700 degrees Fahrenheit. After a temporary drop in tem perature to 1,600 degrees, stabilization at 1,625 degrees Fahrenheit occurred within four minutes. At this time, there were no further traces of dripping wax. At the five minute

interval, temperature was lowered to 1,500 degrees. Through out the next fifteen minutes, temperature was slowly lowered until 1,100 degrees Fahrenheit was reached. Gas and air assist were shut down and the mold removed. As seen in Figure 45, p. 77, carbon deposits were present on three runners, and to some extent, the air vents. Slight amounts

of carbon were present above several wax expansion slits on 77

CH 0

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sam(D 78 the body of the mold. The remainder of the mold was white, and mold damage was not apparent. Nichrome wires were still in place in the shim line area. This ends the discussion of individual dewaxing. Comparisons of FP and CP can now be resumed.

After FP and CP had reached ambient temperature, they were removed from the stainless rack and opened. FP parted easily into front and back sections. The inner mold wall of CP was lifted up and out from the surrounding outer mold wall. The outer mold wall could then be examined. For additional clarity on this point, both the inner mold wall and the outer mold wall are pictured in Figures 46 and 47, p. 79.

The interiors of FP and CP are seen in Figures 48 and 49, p. 80. Close examination of these interiors revealed the gray, powder-like residue left from naphthol crimson (LQ) paint. This residue completely covered detail of the mold inner face. Those areas of the interior not coming into contact with the paint, were clean and white. In addition, the aluminum making up part of the pattern of FP, had melted free from the mold wall. The small, melted mass of aluminum was lifted out, and naphthol crimson (LQ) residue was removed with a brush. This was followed by a directed stream of compressed air to remove loose dust. The appearance of FP and CP after cleaning is pictured in Figures 50 and 51, p.

81. At this point, the next stage in procedure can begin. 79

Fig. 46--Inner mold wall of CP. This half of the mold contains metal feeding channels.

Fig. 47--Outer mold wall of CP. Wax ex pansion slits can be seen on the right side. 80

I. N,) i /

I '/ *~,;** *, A ) f.

p Nt J

N 9' ~LI~ J'i

Fig. 48--Interior of FP mold after flash dewaxing. Aluminum insert is at a.

Fig. 49--Interior of CP mold after flash deviaxing. Residue covers circular areas. 31

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;-~ ;mq~,' ' I * ..~ it~ ~ I 4 'I *

Fig. 50--Interior of FP mold. Residue has been removed.

Fig. 51--Closeup of circular area of CP. Residue has been removed. 82

Rejoining of Ceramic Shell Piece Mold Halves

The rejoining of ceramic shell piece mold halves is a relatively simple operation. First, the mold halves of FP and CP were aligned to approximate their original position before dewaxing. Slurry, thickened somewhat with additional silica flour, was applied to those areas which had been crushed or cut during mold preparation. This, in effect, replaced the mold sections that had covered the edges of the wax shim lines. The application of thickened slurry was allowed to dry for twenty-four hours. Woven fiberglass roving, dipped in slurry, was then applied to cover the complete mold, as seen in Figures 52 and 53, p. 83. The woven fiberglass provides reinforcement to the mold during later metal pour. Once the applied fiberglass has dried, the last stage in procedure can be initiated.

Casting of Ceramic Shell Piece Molds

The procedures involved in the casting of ceramic shell piece molds are identical to casting procedures of whole ceramic shell molds. Prior to metal pour, both FP and CP were preheated separately in the dewaxing furnace described.

FP was preheated at 1,300 degrees Fahrenheit for one hour, while CP was preheated for one hour at 1,350 degrees. At the end of the preheat cycle, each mold was removed from the furnace and placed on dry sand. FP was placed with the impression side facing downward, while CP remained vertical. 83

III! PI-

A, - 1 4~2iI I I I.. ~ ill ~ ~.:-j~ ~ I

Fig. 52--Rejoined mold of FP. Fiberglass roving has been applied.

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Fig. 53--Rejoined mold of CP. Fiberglass roving has been applied. 84

Sand was then packed around each mold. Silicon bronze, at a temperature of 2,100 degrees Fahrenheit, was poured into

FP, while CP received silicon bronze heated to 2,050 degrees

Fahrenheit. The condition of both molds after metal pour can be seen in Figures 54 and 55, p. 85. In these figures, the molds are represented in the position they were in during metal pour. It can be seen that both molds remained intact during metal pour, with no evidence of metal pen etration through the mold wall.

The metal casts of FP and CP can be seen in Figures

56 and 57, p. 86. All ceramic shell molding material was removed by sandblasting. The metal cast of FP, shown in

Figure 56, p. 86, exhibited very good reproduction of orig inal pattern detail. A small hot tear, three-fourths inch in length, occurred along the inside of the projection nearest the left side of the photograph. Metal flash, indicating the parting line of the mold, can be seen around the perimeter. The total weight of metal contained in the mold of FP was twelve and one-half pounds. The metal cast of CP, seen in Figure 57, p. 86, also exhibited very good reproduction of original pattern detail. No significant de fects were noticed on the cast. Metal flash was present on upper and lower shim lines. Total weight of metal contained in the mold of CP was fifty-eight pounds.

Figure 58, p. 87, is a closeup of the completed cast of FP. The pickup of detailed brushwork shows how well the 85

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Fig. 54--Intact FP after casting

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Fig. 55--Intact CP after casting 36

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Fig. 56 --Silicon bronze cast of FP after complete mold removal by sandblasting.

FiG . 57--Silicon bronze cast of CP after ocomple te mold removal by sandblasting. S7

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Fig. 58--Detail of cast surface of FP 88

Fig-. 59--Completed sculpture of CP 89 original pattern has been reproduced. Figure 59, p. 88, is a photograph of the completed sculpture of CP. The upper parabolic shape was cast in a conventional whole ceramic shell mold. It was welded to the lower section which was cast in the ceramic shell piece mold just described.

Results of Principal Experiment 1. Metal casts were produced which had very good re production of the acrylic paint coated patterns. 2. Both FP and CP separated into two halves with no apparent problems during flash dewaxing.

3. Naphthol crimson (LQ) produced a powder-like res idue during the dewaxing procedure.

4. Naphthol crimson (LQ) residue was easily removed with a stiff brush.

5. After residue removal, mold inner face showed no apparent damage. 6. During dewaxing, aluminum insert on FP melted out and away from inner face of the mold.

7. No apparent damage to mold inner face from alum inum insert was observed. 8. Normal ceramic shell dewaxing temperature range used in this experiment resulted in no apparent adverse effects on either FP or CP ceramic shell piece molds. 9. Metal cast into these molds did not break through the molds at any point. 90

10. Metal casts from each mold were free of signifi cant defects, and exhibited very good reproduction of the original pattern. The hot tear mentioned in the description of the cast of FP, is common in casts having right angle cor ners without fillet radii protection (1, p. 151; 2, p. 29).

Analysis of Data

Findings of the principal experiment involving FP and

CP confirmed the results of the pilot test, and provided answers to the questions originally posed by the study:

1. Casts with very good reproduction of the original acrylic paint coated pattern were produced. It is apparent that ceramic shell can be molded over naphthol crimson (LQ) in much the same way that it is molded over expendable wax. 2. During flash dewaxing, both FP and CP separated into two halves with no apparent problems. Separation of the mold allowed examination of the mold interior. 3. Naphthol crimson (LQ) paint produced a powder-like residue during the dewaxing procedure. This residue was easily removed, leaving a defect-free inner face. This points out that naphthol crimson (LQ) has no particularly damaging effect on ceramic shell material during flash de waxing. It can be speculated that naphthol crimson's effec tiveness as a pattern material is due either to its synthetic

organic pigment content, or, to its singular use during test ing without inorganic pigment combinations. 91

4. During dewaxing, the aluminum insert on FP, coated with naphthol crimson (LQ), melted out and away from the mold inner face, and was easily removed. No apparent damage to the ceramic shell was observed. This indicates that this particular shape and thickness of aluminum, coated with specific acrylic polymer paint, can function as part of a wax pattern in ceramic shell molds.

5. Temperature ranges used for dewaxing of molds in this experiment were within the range normally used for conventional whole ceramic shell molds. An absence of in terior or exterior defects on the experimental molds points out that this range of temperature will produce satisfactory molds.

6. Metal casts from each mold were free of significant defects, and exhibited very good detail reproduction of the original pattern. This indicates that any chemical or thermal reactions between the acrylic polymer paint coat and the mold are not significant enough to be evident on gross examination of the metal cast.

7. Metal cast into each of these molds did not break through the mold at any point. This indicates that the bond joining the mold halves together is of sufficient strength to keep the mold intact and functional.

I -w ,"; 4 . I lo -I "I - ". -- ,- CHAPTER BIBLIOGRAPHY

1. Hinkle, J. W., "An Orderly Approach to Investment-Cast ing Design," Machine Design, 39 (December, 1967), 151. 2. Sylvia, J. G., Cast Metals Technolgy, Reading, Massa chusetts, Addison-Wesley Publishing Company, 1972.

92 CHAPTER V

SUMMARY AND CONCLUSIONS

The major concern of this study was to determine the feasibility of using nonexpendable patterns in ceramic shell molds. If it were proven that these materials could be used together, to produce metal casts with good fidelity of de tail, the sculptor could be provided with an alternate to the traditional wax pattern.

The value of being able to use nonexpendable materials in ceramic shell molds can be shown by comparing the process used in this study to those procedures normally used with wax patterns. Given a specific model containing nonexpend able materials, this study proceeds directly into ceramic shell molding. In the traditional approach with whole ce ramic shell molds, other factors must be considered. First, a flexible mold of some sort must be taken from the original model. Wax must then be painted or injected into the flex ible mold to produce a wax pattern similar to the original model. Only then can ceramic shell molding be initiated. Granted, this study has been limited to flat and hollow cyl indrical patterns with nonexpendable materials located on the patterns in specific places, and therefore, does not pretend to apply to all instances in which nonexpendable

93 94 materials could be used.

Questions concerning materials, molding procedures, de waxing time, preheat, etc., are understandably of paramount

importance to the sculptor making preliminary investigations into the ceramic shell process. All too often, this infor

mation in sculpture texts is inadequate, limited or con fusing. Additionally, periodicals devoted to art appear to deny the existence of ceramic shell molding, for it is rarely

discussed. Hopefully, this study will serve to clarify at

least one method of working with ceramic shell. In Chapter I, the ceramic shell process and its advan

tages over sand and plaster molds was briefly discussed.

The possibility of using controlled fracture for removal of

nonexpendable materials from ceramic shell molds was then

introduced. Questions arising in this study were concerned with the feasibility of using nonexpendable materials in ceramic shell piece molds. The study was limited to the use of ceramic shell, in sculpture, in the construction of piece

mold configurations, designed specifically for removal of flat patterns and hollow, cylindrical patterns. These pat

terns were constructed of wax combined with aluminum and/or acrylic polymer paint. The significance of the study centered on adding spe

cific nonexpendable materials and alternate ceramic shell

molding procedures to the list of expendable materials in

use with conventional ceramic shell process. Alternative 95 methods of manipulating surface texture and design of metal casts are thereby offered to the sculptor. In Chapter II, related literature dealing with the

origin and development of two distinct thin-walled molds was discussed. These two molds were identified as the

Croning Process mold and the ceramic shell mold. Attention

was directed to methods used to join half molds produced by

the Croning Process, for these methods are similar to join

ing methods used in the present study. The relationship of the ceramic shell mold to traditional investment block

molds used in industry was pointed out. Problems encoun

tered in dewaxing of ceramic shell molds were described.

Eventual solution of these problems was noted. Mention was then made of the national introduction of the ceramic shell

process to the artist. Reports from sculptors using the ceramic shell process were cited. Of special interest in

these reports was the use of fiberglass for mold repair or reinforcement, and removal of debris from ceramic shell molds.

The pilot study, recounted in Chapter III, was initi

ated to determine the feasibility of using nonexpendable

patterns in ceramic shell molds. Three pilot study tests on nonexpendable patterns were carried out. Pilot Study Test I dealt with flash dewaxing of wax patterns coated with identified acrylic polymer paints. This was done to deter mine the effect of nonexpendable materials on ceramic shell 96 molds, and on metal casts made from these molds. Results not indicated that identified acrylic polymer paint would crack the mold during normal flash dewaxing, but produced resulted residue in the mold. Extremely poor metal casts because of this residue. Pilot Study Test II encompassed separation and re

joining of ceramic shell mold segments. Identified acrylic from polymer paints were used as coatings on the patterns which the molds were made. After normal flash dewaxing,

sand and compressed air were introduced into the mold of

Pilot II-1 in an unsuccessful attempt to dislodge the

residue inside. This same mold sample was cut apart, re and cast. joined with slurry, reinforced with fiberglass, Results indicated that the mold could be successfully re

joined after cutting, and could contain molten metal. Pilots 11-2 and 11-3 were designed for mold separation by incorporating wax shims into the acrylic coated patterns. During dewaxing, wax shims were consumed and separated the

molds into front and back halves. Temperature ranges in dewaxing were those used in normal ceramic shell procedures, 11-2 and produced no damaging effects. Further, in Pilots and II-3, the acrylic polymer paint napthol ITR crimson (LQ)

was shown to be a preferred choice over other paints used.

Pilots 11-2 and 11-3 were cleaned of residue and sealed with thickened slurry. Mat fiberglass was used for reinforcement 97

used for of Pilot 11-2, while woven fiberglass roving was was this purpose on Pilot 11-3. Casting of Pilot 11-2 unsuccessful. Metal breakout resulted from weak bonding of a sealed half sections. Casting of Pilot 11-3 produced cast with good reproduction of the original pattern, but with some defects. This pointed out that reinforcement to along the sealed border of Pilot 11-3 was sufficient contain metal. In Pilot Study Test III, modifications were made to the

patterns of Pilots III-1 and 111-2. These modifications were made to enable the finished molds to be poured while

they were in a flat position on the sand bed. Previous molds had been poured resting on one edge in a vertical coated position. Pilot III-1 was fitted with aluminum and with napthol ITR crimson (LQ). Aluminum and naphthol crim

son (LQ) were added to Pilot 111-2. The molds of these Pilots were flash dewaxed, sealed with thickened slurry, reinforced with woven fiberglass roving, and cast. Results indicated that wax shims performed as mold separators, and

normal ceramic shell dewaxing temperatures were effective

for these molds. Napthol ITR crimson (LQ), naphthol crim

son (LQ), and aluminum produced good mold impressions.

Damage to the mold wall was not evident after dewaxing. Molds remained intact during casting, and produced casts with very good reproduction of the original patterns. This

revealed that the ceramic shell piece mold was effectively 98 designed, and could function as planned.

Chapter IV was concerned with the establishment of pro cedural technique for utilizing the ceramic shell piece mold in sculpture. A flat pattern and a hollow cylindrical of data in pattern were chosen for production. Sources cluded 1) photographic documentation of each pattern, mold, and cast; 2) written observation of the condition of each and tem pattern, mold, and cast; 3) data reports of time mold; perature ranges used during flash dewaxing of each 4) data reports of time and temperature ranges used during temperature of preheat of each mold; and 5) data reports of silicon bronze immediately prior to pouring of each mold. Procedural technique to be followed was divided into these stages:

1. Pattern construction

2. Formation of the ceramic shell piece mold

3. Dewaxing and separation of the ceramic shell piece mold into halves

4. Rejoining of ceramic shell piece mold halves 5. Casting of ceramic shell piece molds

It was noted that the stages concerned with formation of the ceramic shell mold and metal casting, were identical to

stages used with conventional whole ceramic shell molds. Further, stages 1, 3, and 4, which were descriptions of pat tern construction, dewaxing and separation, and rejoining, were departures from standard ceramic shell procedure. 99

the Results of the principal experiment, which confirmed findings of the pilot study, were presented. The chapter concluded with an analysis of the data.

Conclusions

1. An analysis of the results of the principal ex process can be periment points out that the ceramic shell as well. This expanded to include piece mold configurations nonexpendable ma opens up the possibility of using numerous molds. terials as patterns for metal casting in ceramic shell 2. The nonexpendable materials tested in this study- and aluminum--had naphthol crimson (LQ) acrylic polymer paint no adverse effect on the strength of the mold or the inner

face of the mold. It can be speculated that the successful

use of naphthol crimson (LQ) is due either to its synthetic use without organic pigment content, or, to its exclusive mixtures of inorganic pigments. When used in the manner

described, it appears that there should be no particular concern about these substances causing mold deterioration. also molded 3. The tested nonexpendable materials were directly in ceramic shell. This removed the expensive and time consuming task of flexible rubber or silicone mold fabrication.

4. The removal of residue left in the mold after de

waxing of the materials tested, hinged on controlled frac ture of the mold wall. Controlled fracture was accomplished 100

the original pat by using wax shim lines incorporated into to brass tern. The wax shim lines, identical in function consumed shim lines used to divide plaster molds, were of the mold during flash dewaxing. This led to division residue. into two halves, which were easily cleaned of tested were success 5. The ceramic shell piece molds for whole fully flash dewaxed at temperatures recommended special ceramic shell molds. Additional precautions or were handling instructions for dewaxing of these molds thereby eliminated. 6. Finally, the ceramic shell piece molds tested pro in the duced accurately detailed metal casts. Variations ceramic shell weight of these casts indicated that the a significant metal piece mold functioned effectively within containment range.

Recommendations for Further Study

Based on this study, recommendations for further study

on ceramic shell piece molds designed for nonexpendable ma terials include the following statements: l. Ceramic shell piece mold configurations for larger

and more complex three dimensional forms should be investi gated.

2. Acrylic polymer paints should be studied in order

to determine why some work effectively as pattern coatings while others do not. 101

materials to be used 3. A wider range of nonexpendable with wax patterns should be explored. used 4. The use of multiple nonexpendable substances

in combination should be studied for possible use as pat tern material in ceramic shell piece molds. materi 5. The practicality of locating nonexpendable als on wax patterns in such a manner as to allow their spe would eliminate cific removal should be investigated. This the need for opening the entire mold in some instances. for 6. The possibility of using the wax shim principle patterns, joining large molds should be pursued. Sculpture could perhaps judged too large for handling during molding, with be divided in half. Each wax half could be provided ceramic wax flanges. The halves could then undergo separate the halves shell molding and flash dewaxing. After dewaxing, could be rejoined along the flange area, and cast. sprayed 7. The use of nonpigmented acrylic polymer, and petroleum liquid wax, plastic sprays, plastic films, based paints, should be explored for use as mold release shell. agents for nonexpendable materials used in ceramic 8. Other methods of rejoining ceramic shell piece molds

should be studied in order to reduce the time spent on this particular stage of the process. melts out 9. The observation that thin gauge aluminum study at flash dewaxing temperatures, indicates that further

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shell molds is of its use as pattern material in ceramic warranted. be found. 10. Substitutes for fused silica sand should

This sand, applied after the dipping procedure, is quite be willing to use expensive. Perhaps more students would reduced. the ceramic shell process if expenses could be 11. Surveys of other college and university art de the ceramic shell partments should be made on the use of used by each school. process and variations of this process be estab A bank of information on the process could then approach lished for the student sculptor interested in this to metal casting.

12. Even though it is expensive, the ceramic shell part of under process should be included as an essential can serve as an ex graduate studies in sculpture, for it citing introduction to the art of metal casting. Small not require the sculptures could be produced which would student to spend great sums of money. begin 13. Research on the ceramic shell process should the on the graduate level. Extensive reading required on any re subject, coupled with difficult scheduling, make search effort a rather long and involved procedure. It accept these is quite likely that the graduate student would undergraduate responsibilities more readily than would the student. BIBLIOGRAPHY

Books

Irving, Donald J., Sculpture: Material and Process, New York, Van Nostrand Reinhold Company, 1970. Reading, Massa Sylvia, J. Gin, Cast Metals Technology, chusetts, Addison-Wesley Publishing Company, 1972.

Taylor, H. F., M. C. Flemings, and J. Wulff, Foundry Eng neerin, New York, John Wiley and Sons, Inc., 1959.

Verhelst, Wilbert, Sculpture: Tools, Materials, and Tech Hall, niques, Englewood Cliffs, New Jersey, Prentice Inc., 1973.

Articles

Albin, J.,"Equipment and Material for Precision Casting," Iron Age, 154 (November, 1944), 52. Birdsall, G. W., "Casting Supercharger Buckets at Allis Chalmers," Steel, 116 (January, 1945), 96. "British Claim Patent Rights for Shell Molding," Iron Agj, 171 (January, 1953), 99o Brooks, Dennis, "Clamping Shell Moulds," Canadian Metals, 17 (January, 1954), 24. "Ceramic Shells Solve Problems on Heavy Complex Castings," Iron Agj, 186 (July, 1960), 102-104. Chase, Herbert, and Leslie T. Schakenbach, "New Precision Casting Process Provides Better Finish, Closer Toler ances," Materials and Methods, 29 (March, 1949), 56. Collins, L. W., Jr., "Ceramic Shell Mold Boosts Investment Casting Weight to 100 Pounds," Machinery, 67 (October, 1960), 123-125. Deakin, R. C., "Checklist for Casting Processes," Machine Design, 46 (February, 1974), 126.

103 104

Dunlop, Adam, "Ceramic Shell Moulds," Metal Industry 96 (April, 1960), 287-290. Glaser, J. W., "Refractory Molds for Precision Casting," Iron Age, 155 (February, 1945), 52-54. J., and Philip Manganaro, "Ceramic Invest Grant, Nicholas 110. ment Shells," Tool Engineer, 38 (February, 1957), Process and Green-Spikesley, E., "Investment Casting; The the Product," Metallurgia and Metal Formin, 42 (July, 1975), 208.

Herb, C. 0., "Ford Produces High-Speed Steel Cutters by Precision Casting," Machinery, 51 (April, 1945), 149-150. Invest Herrmann, R. H., "Ceramic Shell Process to Expand ment Casting Market," Foundry, 88 (August, 1960), 158, 161-162. J. W., "An Orderly Approach to Investment-Casting Hinkle, 151. Design," Machine Design, 39 (December, 1967), Methods Katz, M. L., and S. B. Donner, "Improved Closing Cut Shell Casting Costs," Iron Ae., 173 (June, 1954), 113-115.

McCullough, William W., "Precision Molding Process Employs Resin Binder," Foundry, 76 (October, 1948), 130.

Merrick, Albert W., "Precision Casting of Turbosupercharger Buckets," Iron Age 153 (February, 1944), 54-56.

"Mono-Shell Process," American Machinist, 101 (July, 1957), 138. Neiman, Robert, "Precision Castings Employing Dental Tech nique by Investment Molding Process," American Foundry man, 6 (September, 1944), 5.

Neimeyer, William I., "Precision Casting with Frozen Mer cury Patterns," Iron Ag, 163 (March, 1949), 97. "New Glass-Powder-Mold Precision Casting Process Eliminates Knockout, Investment Materials," American Machisist, 100 (June, 1956), 170-171. 84 "New Molding Process Uses Glass Shell Molds," Foundry, (August, 1956), 218-219. 105

"One Hundred Years of Metalworking; Casting," Iron Ag, 175 (June, 1955), B-Il. "Precision Mouldings" Metal Industry, 71 (December, 1947), 506. Ceramic "Prepare and Use Ceramic Investment Shell Molds," Indu try, 76 (April, 1961), 122-125.

Roast, Harold J., "An Appraisal of the Shell Molding Pro cess, " Metal Progress, 61 (April, 1952), 71. Rueter, Raymond, "Ceramic Shell Mold Experiments," Metal Progress, 75 (May, 1959), 148. Scheffer, Karl, "Fundamental Aspects of Ceramic Shells in Precision Casting," Metal Progress, 75 (May, 1959), 144.

"Shell Molding; Ten Years of Progress," Foundry, 86 (April, 1958), 80.

Tindula, Roy W., "Current Status of the Shell Molding Process," Foundry, 80 (July, 1952), 204-206. "Two New Ways to Fasten Shell Mold Halves," Precision Metal Forming, 12 (April, 1954), 99.

Unterweiser, P. M., "Single Glass Mold Smoothes Casting Wrinkles," Iron Age, 177 (May, 1956), 92-94.

Reports

Colson, Frank A., "Problems in Ceramic Shell," Proceedings of the Fifth National Sculpture Conference, Lawrence, Kansas, University of Kansas, 19T8.

Colson, Frank A., and Thomas Walsh, "Problems in Ceramic Shell-Question Session," Proceedings of the Fifth National Sculpture Conference, Lawrence, Kansas, University of Kansas, 1968.

Nalco Chemical Company. Investment Casting, Chicago: Nalco Chemical Company, n. d. Schnier, Jacques, "Ceramic Shell Molding for Sculpture Cast ing," Proceedings of the Third National Sculpture Cast inConference, Lawrence, Kansas, University of Kansas, 1964. 106

Turnbull, J. S., "Development of Lost-Wax Process of Pre cision Casting, 1949-1953," Proceedings, Institution of Mechanical Engineers 169 London, England, House of the Institution, 1955.

Unpublished Materials Penland, L. C., "Expanded Plastics Used as Sculptural Patterns for Burn Out in Ceramic Shell Molds," unpub lished doctoral dissertation, Department of Art, North Texas State University, Denton, Texas, 1976.