Understanding How to Control the Drying Process of Acrylics Acrylic Waterborne Paints Tend to Dry Extremely Quickly

JUST PAINT

Published by GOLDEN Artist Colors, Inc. / Issue 3

Dry Notes on Drying! Understanding How to Control the Drying Process of Acrylics Acrylic waterborne paints tend to dry extremely quickly. This is not earth shaking news for anyone who has explored acrylic paints. For some, this is the Acrylics greatest advantage and for others its greatest weakness. Several techniques and additives can extend wet time on the palette, on the surface, on the tools and even in the containers. In this article, we will review the mechanism of drying of acrylic paint and how that process can be controlled and manipulated to an artist’s advantage. Paint Drys As Water Evaporates Waterbased acrylics dry as the vehicle that carries them -- mostly water -- evaporates. As water evaporates, or is Thickly applying gels or watering down mediums can lead to stresses absorbed by the substrate (canvas, paper, within the film causing crazing upon drying gesso, etc.), the microscopic acrylic polymers, which are shaped like spheres, are forced into ever closer contact. point, but the paint no longer flows easily. longer sufficient water to keep the acrylic Eventually they’re crowded so tightly that Another indication is that the brush begins polymer from forming a film. For very the spaces between them create capillary- to drag over the surface. The paint doesn’t thin films this could occur within minutes, forces, and water is actually pulled from seem dry, yet it is difficult to move and while the time for thick films to skin over the paint film. This capillary action packs fairly sticky. This is often a point where may be a full day. the acrylic spheres against one another in a overworking the acrylic will cause the The third stage of drying is the honeycomb-like pattern, and permanent clouding of glazes or time required for the entire thickness of clear coats. This stage is marked the film to be thoroughly dry. That is they begin to form a more or ▲ less continuous, cohesive film. physically in the paint film by a when the remaining water and solvent As this occurs, the polymer PAINT DRIES dramatic reduction in water (used as freeze-thaw stabilizer and IN 3 DIFFERENT spheres deform and partially content at the surface. However, coalescent) evaporate and leave the film. STAGES. since evaporation is still This is a most crucial time frame to be combine with one another in a DRYING TIMES process of film formation called SHOULD BE occurring very quickly from aware of as the ultimate physical proper- coalescence. THOUGHT OF layers below, no film formation ties, such as adhesion, hardness and clarity, Three stages of drying IN SEVERAL has yet taken place. In very thin do not fully develop until the film is near DIFFERENT TIME paint films this can occur within complete dryness. For very thin films, this Paint actually dries in FRAMES. seconds. time may be a few days, while films of 1/4 three very different stages, ▼ In the second stage of inch thickness or more will take months hence drying times should be drying the paint actually forms a and up to a year to be completely dry. thought of in several different skin over the surface. This is the time frames. The first stage results in the Moving Artwork time when people frequently judge the formation of a semi-dry surface. No film Many artists are not aware of this paint as, “dry to the touch”. There is no formation has actually occurred at this sometimes lengthy drying time. Often Continued next page... Just Paint / Issue 3 2

Continued from Front... cases treatment in a desiccant cabinet with temperature and humidity conditions. Drying Notes reduced humidity may be necessary.) Practical Considerations: paintings can be ruined if painted Environmental Considerations There are no limitations for very thickly and moved during this period Environmental factors that regulate applying additional acrylic paint. That is, of drying. In very thick paintings, three the evaporation of water also influence the you can apply acrylic paints while the weeks is a minimum before moving the drying times of acrylic paint films. These underpainting is still wet, just skinned work, as cracking may include: temperature, over, or has dried for several years. (If occur within the region humidity and airflow. painting over an old acrylic surface, be sure of the film not thor- Temperatures below to clean off any accumulated dirt or oughly coalesced. Until 49oF (9oC) will not grime). If you are going to apply oils over complete coalescence or allow the acrylic the acrylic underpainting, wait until the film formation has been polymer solids to acrylics are completely dry. achieved, the paint will properly coalesce to For varnishing, it is also best to wait not reach its optimum form a continuous film, until the painting is completely dry. performance in adhesion, and may result in film Trapping excessive levels of water and/or durability or block failure (cracking, solvent, may result in clouding or poor resistance (reduced tack adhesion failure, initial adhesion of the varnish. This is more of the surface). Addition- powdered film, etc.). important when the varnish forms a tight, ally, clear films of gels, Relative humidities in low-permeable film, such as in the case of clear mediums, or lightly excess of 75% will slow GOLDEN MSA Varnish. When a top coat colored glazes will not the evaporation of is more open, or permeable, such as an reach total clarity until water from the surface, isolation coat of GOLDEN Soft Gel, the completely dry. slowing the drying degree of drying is less crucial. When using Blanching or clouding process. While a GOLDEN Polymer Varnish, which is a may occur in works that moderate and steady waterborne product, the paint film must have appeared clear, and airflow in the drying also be completely dry underneath. are then stored away in a area is favorable for Applying this varnish over drying paint may damp basement or on thorough drying, a result in tackiness, clouding or even top of each other. These strong breeze, especially cracking. films may not have been one directly on the Controlling Drying Time: thoroughly dry, or the paint surface, can cause Depending on the objectives and storage conditions film formation failure, techniques, artists have varying needs to caused them to trap such as cracking and/or keep paint from drying too quickly. They moisture. Given enough wrinkling. Tempera- may require longer mixing time on the time for more complete drying, clarity, tures of 70 to 85oF and humidities under adhesion, block resistance and hardness 75% are ideal. Yet acrylics have been very may improve dramatically. (In very severe successfully painted within a wide range of Continued page five... ABSTRACT

Study Reveals Causes for ‘Support Induced Discoloration’ by Mark Golden, President Jim Hayes, Technical Director Ben Gavett, Assistant Technical Director This study was conducted by Support Induced Discoloration (SID) is more evident in thicker, more transparent applications. Golden Artist Colors, Inc. and Buffalo State University Department induced discoloration” (SID), comes translucent acrylic mediums. of Conservation. The researchers at from the water soluble components This paper, available from Golden had uncovered a phenomena in unwashed canvas, linen, and Golden, is the reprint from the of discoloration previously not masonite. The effect is particularly 1991 symposium “Saving the described within the literature. This evident in very transparent glazes or Twentieth Century, The Conservation discoloration, coined “support thick applications of transparent and of Modern Materials”, held in Canada. GOlDEN ARTIST COLORS Just Paint

Most waste is disposed of into avoid disposal of these by purchasing Glamour, Fame either the water, ground, or air. only what will be entirely used. The United States Environmental • Before using water to clean palettes, and Fortune Protection Agency, state agencies, brushes, containers and other tools, and local authorities all have wipe them with a paper towel and Available regulations affecting such disposal. allow it to dry before disposal. This Questions are best addressed to makes the wash water stay cleaner Without Effort the local facility first, such as the longer and keeps paint solids from landfill or water treatment plant.1 going down the drain. or Sacrifice! Questions about whether or not a • Solids in washwater can be further Please don’t be disappointed, material is considered a “hazard- minimized by removing them with a simple treatment process. See the ous waste” and the best method but this article is really about the other side for further information on for its disposal, can also be di- best alternatives for disposing of treatment process. wastes generated while painting. rected to the manufacturer. I know it is a lousy trick, but the TIPS TO Editor insists on captivating TIPS ON BEST headlines. However, there are real DISPOSAL REDUCE WASTE benefits to doing a good job with • Purchase products in the optimal PRACTICES container size. Buying too small results waste management practices, and in more packaging wastes. Buy too if you stay till the end of the • Even with water-based products, it is best to discard a solid instead of much, and you risk having more than article, you may come away with washing everything down the drain. can be used or having the product fail some Also, liquid paint should not be taken during storage. new ideas. - Ben Gavett to a landfill. If allowed to dry, film- • Use work practices that minimize forming paints such as acrylics lock wasted paint. For acrylics, try a There are a few generalizations pigments in place and help prevent moisturizing palette and keep the about waste disposal that are them from moving around in the paint covered as much as possible. universally true. First, it is best for groundwater. Allow residual paints • Store products to maximize shelf life. the health of the planet and its and mediums to dry in the container. Avoid extremes of temperature, inhabitants if the byproducts of Dispose of as is, or remove the especially freeze-thaw cycles. Make our creativity are kept to an subsequent paint skin, leaving a fairly sure lids are kept tight. Clean dried absolute minimum and the issue clean container. GOLDEN Acrylics paint from the threads of jars and lids of disposal is avoided entirely. are packaged in HDPE plastic, which before closing to help get a better seal. Next, when wastes are produced, can then be reused or recycled in • If products are still usable, but just the manner of disposal which will many areas. aren’t needed, give them to someone have the least negative impact • Small amounts of solvent-based who can use them. If properly labeled upon the environment should be products, like GOLDEN MSA and nontoxic, many nonprofit selected. Finally, the legal require- Varnish, can usually be allowed to organizations with art and craft ments for disposal depend upon evaporate. After complete drying, the programs would appreciate a donation the nature of the waste produced, container can be disposed of in a of materials. where it originates, and who is regular landfill. Significant amounts of • Recycle old acrylic paintings. Apply a responsible for it. For example, these products are considered new gesso ground and use them for disposal options will depend in hazardous wastes and should be taken studies. They are also useful for practicing varnishing techniques and part upon the classification of the to a local Hazardous Waste Collection preevaluating the inevitable visual waste generator. Wastes generated Center. Be careful, some of these limit effect a varnish will impart. outside of the household, such as their service to households and by a small manufacturing business exclude small businesses. An expensive Footnotes: 1 or store, have tighter disposal hazardous waste disposal service must For an overview of waste disposal restrictions. Alternatives will also then be utilized. In addition to regulations, send self-addressed, stamped solvent-based products, other art depend upon how hazardous a envelope for Waste Management and materials which are hazardous when Disposal for Artists and Schools, from the waste is, based on reactivity, disposed of include etching acids, Center for Safety in the Arts at flammability, toxicity and physical pressurized aerosol cans, and certain NYFA,155 Avenue of the Americas, state (solid, liquid, or gas). highly toxic pigments. It is best to 14th Floor, NY, NY 10013. GOlDEN ARTIST COLORS Just Paint Removing Water-Based Paint Solids from Rinse Water

If you would rather not flush water Start by assembling the supplies per gallon being processed (a scant laden with acrylic paint solids down the listed below. Decide on the process batch 3/4 Tablespoon). Stir in vigorously and drain, they can be removed prior to size. Using 5 gallon pails allows you to observe. The flocculation of solids should disposing of the water. This process process up to 2 1/2 gallons at a time. A 1 start occurring within a couple of consists of chemically treating the gallon pail and matching funnel allows minutes. You should start to see a clear contaminated water to cause the solids to for up to a 3/4 gallon batch. layer of water forming very quickly as the flocculate, followed by filtering to 1. Add 10 grams of granular solids settle to the bottom. If, after several remove them from the water. The aluminum sulfate for each gallon of minutes, flocculation has not occurred, materials and equipment needed are water. This is about a 1/2 Tablespoon, repeat steps 1 and 2. available locally and/or via mail order well-rounded. So, 2 1/2 gallons would 3. Check the pH of clear water. from the “Vender List” attached. The require about 25 grams, or 1 1/4 It should be between 5 and 9. If lower, chemicals are hazardous so read label Tablespoons. Dissolve this material in a adjust by adding lime. If higher, adjust precautions and keep everything out of small jar with several ounces of water by adding aluminum sulfate. the reach of children. The process before adding to waste water.. Then, add 4. Assemble the filtering equipment described is intended for nonindustrial to waste water and stir vigorously. as shown. Use 2 coffee filters at a time. users of acrylic paints. 2. Add 9 grams of powdered lime Pour the water through the filters after flocculation has occurred. The water will take several hours (over night) to completely pass through the filter. The resulting filtrate should be clear and SUPPLIES NEEDED TO should be flushed to a sanitary sewer. The solid filtered residue should be PROCESS RINSE WATER disposed of in a licensed landfill. PAPER COFFEE FILTERS Vendor List The largest size we found can hold 2.5 gallons. These work well Filters may be found at restaurant when using a 5 gallon pail. There is also a size available which works with a 1 gallon pail. See vendor list. supply houses. We use “Brew Rite” 18" x 7.5" for the 1 gallon setup and 25" x PLASTIC FUNNEL 11" for the 5 gallon, purchased from Sized to match the filter and pail being used. Smith Restaurant Supply Co, Inc., 2 PLASTIC PAILS 500 Erie Boulevard East, Syracuse, NY Depending on amount of rinse water being processed, 13202, Phone 315-474-8731. 1 or 5 gallon size. Polyethelene. Funnels need to be large enough to STIRRING PADDLE rest on rim of pail. Check with industrial Common paddle as available supply firms, such as McMaster-Carr, at Hardware or Paint Store. 473 Ridge Road, Dayton, NJ 08810; ALUMINUM SULFATE Phone (908) AND HYDRATED LIME 329-3200. Order the 13.5" diameter Commonly available at Gardening Centers. #4360T6 for the 5 gallon setup and the 9" #4144T4 for the 1 gallon. Pails, such as the polyethylene type that hold our products, work fine. Aluminum Sulfate and Hydrated Lime are common soil amendments available from gardening centers. pH paper is available from labora- tory supply houses. Measuring spoons should be purchased and kept separate from kitchen utensils. WEIGHING DEVICE OR pH PAPER MEASURING SPOONS Commonly available (Do not use Mom’s baking set) from Laboratory Supply Houses. 3/96 5 Just Paint / Issue 3

Continued from page 2... Some people prefer to lightly mist using a very wet sponge or rag. After a the paint on their palettes. This can be a period of 3-5 minutes the paint film should Drying Notes very effective technique to provide more be soft enough to be easily scraped or palette, or longer blending time on open time, as it stops the first stage of peeled off. the canvas or other support. drying. A simple plant mister, obtained at a On The Surface: There are as many ways to control hardware or drug store, may be filled with Sealing canvas and other substrates the drying process as there are ways to water (recommend distilled or deionized) may be the most dramatic way of increasing control the evaporation of water. High or a 10:1 water/retarder mixture, for this the open time of acrylics. As opposed to humidity, low temperature, low air flow, purpose. Note again, that excessive levels of evaporation, very absorbent surfaces can thick application and nonabsorbent retarder will result in a weakened paint almost immediately wick the water out of surfaces slow the drying of acrylic paint. film, that remains sticky. Excessive spraying the acrylic and cause skinning. Several years Conversely, dry conditions, high tempera- may cause colors to drip, or to stain into ago an artist called us, complaining that our tures, significant air flow, thin application the support in an undesirable manner. Heavy Body Acrylic was drying too quickly and absorbent surfaces speed the evapora- On the market are several varieties on her paper. When she first encountered tion (or absorption) of water, and the of plastic palettes that help keep acrylic the problem, she decided to slow down the drying process. paints in working condition. The most drying by adding more water to the paint. Some situations call for chemical effective is the Stay-Wet Palette®, which Intuitively, her approach made sense, but agents that retard the drying of acrylic takes advantage of what we know about when she added water, the paint dried even paint. These are usually a blend of several acrylic drying: That is, if you control the more quickly. What was happening was materials, predominantly glycols. By atmosphere, you control the acrylic. The that the drying was not controlled by evaporating far more slowly than water, Stay-Wet Palette® is a large plastic tray on evaporation, but more so by absorption they keep the polymer spheres apart, which you place a large, flat sponge. After into the substrate (paper), which hadn’t preventing early coalescence. Retarders are soaking the sponge in water, a special filter been sealed. As she thinned the paint, it not extremely effective if you need the paint paper is placed over it which acts as a had less hold-out, and the water was to stay wet in thin films or on very palette surface. The filter paper allows absorbed more easily into the paper. Had absorbent surfaces. Humectants -- agents water vapor to permeate, keeping the she sealed the surface first with a Polymer that absorb or hold water, like glycerin -- paints moist. If the sponge stays wet, paints Medium or skim coat of Soft Gel Gloss, also have been added to retard or slow will remain wet for hours without the use the substrate would not have absorbed as drying. However, humectants must be used of a retarder. This palette has a cover to much water, and drying would have been with extreme care as they tend to percolate further extend working time. Some artists controlled more by evaporation. to the surface of the film during drying, have suggested that the Stay-Wet Palette® A cool air humidifier may prove leaving a residue that may reduce inter-coat slightly dilutes acrylic colors, but if you useful to increase the localized relative adhesion. plan to work outdoors with acrylics on a humidity, and thus slow the drying process. On The Palette: palette, the Stay-Wet Palette® is nearly a Directing the cool moisture flow In addition to additives, several necessity. techniques will help keep paints wet on the When paint dries on a glass or plastic palette, the best way for removal is palette. A most important first step is to ...Continued next page use a non-absorbent palette. Glass works to saturate the dried surface with water, nicely, as do plastics such as polyethylene. Glass stays fresh and free from stains and works well as long as it doesn’t break. The New Color Mixing ABSTRACT problem with a glass palette tends to be the weight. A new commercial tempered-glass Guide and Mixing Set palette made in several sizes, has conve- nient hand-sized holes for carrying. Many for GOLDEN Acrylics artists construct their own glass-topped Throughout history painters and taboret to use with acrylic paints. On wheels, the glass palette is portable and the authors have recommended various artist can use larger plates of glass without palettes of color. Some give insight worrying about excess weight or breakage. of the painter’s working style. Others To slow the drying of paints on glass offer a simple palette for mixing but or plastic palettes you may use a small typically limit color possibilities. We amount of retarder. About three to ten have created a palette of eight percent of GOLDEN Retarder will keep a mass of paint from forming a skin for up to professional acrylics to provide you four to six hours, depending on the ambient the potential to mix the widest range conditions. Excessive quantities of retarder, of colors. especially when working in thicker impasto, For a copy of the Mixing Guide, will leave the paint skin feeling like soft including a full color, visual mixing gum, as the glycol may not totally release from the film. reference, phone 1-607-847-6154.

Golden Artist Colors, Inc. Colors, Artist Golden

working properties of the paint. the of properties working

Copyright ©1996. All rights reserved. rights All ©1996. Copyright

the paint surface) of the film. the of surface) paint the overuse conditioner, as it may affect the affect may it as conditioner, overuse

cause ferrotyping (transferring a texture to texture a (transferring ferrotyping cause

acrylic that will stick. Be careful not to not careful Be stick. will that acrylic 607-847-6767 FAX:

surface. Even polyethylene sheeting may sheeting polyethylene Even surface. well-conditioned will reduce the amount of amount the reduce will well-conditioned

607-847-6154 Phone:

worst offenders, often sticking to the acrylic the to sticking often offenders, worst up of your brushes. Keeping your brushes your Keeping brushes. your of up

Bubble wrap, paper and glassine are the are glassine and paper wrap, Bubble

conditioner will greatly improve the clean the improve greatly will conditioner

USA

important for newly completed works. completed newly for important brushes with a small amount of brush of amount small a with brushes

New Berlin, NY 11341 NY Berlin, New

touch the paint surface. This is very is This surface. paint the touch hasn’t been abused. Pre-conditioning abused. been hasn’t

GOLDEN Artist Colors, Inc. Colors, Artist GOLDEN Publisher: to let anything other than air than other anything let to not important cleaners will work well, as long as the brush the as long as well, work will cleaners

humidity. When shipping artwork, it is it artwork, shipping When humidity. most of the commercially available brush available commercially the of most

avoiding extremes in temperature or temperature in extremes avoiding Ben Gavett Ben dried paint from tools. For hardened paint, hardened For tools. from paint dried

front and back of the paintings, while paintings, the of back and front

detergent added to water will help remove help will water to added detergent Jim Hayes Jim

drying, is to have ample air flow over the over flow air ample have to is drying,

the brush. If needed, a small amount of dish of amount small a needed, If brush. the Mark Golden Mark Writers:

for paintings that are in the process of process the in are that paintings for

the base of the ferrule, will start to harden to start will ferrule, the of base the

Issue 3 / March 1996 March / 3 Issue thoroughly dry. The preferred conditions preferred The dry. thoroughly building up over time, working its way into way its working time, over up building

Just PaiNT Just

or put into any enclosed environment, until environment, enclosed any into put or pointed up. Even a small amount of acrylic of amount small a Even up. pointed

Generally, a painting should not be moved be not should painting a Generally, storing brushes with the bristles, or hairs or bristles, the with brushes storing

arranging for storage and shipping. and storage for arranging paint from hardening on them. Avoid them. on hardening from paint

paint needs to be considered when considered be to needs paint

Tools should be kept wet to keep to wet kept be should Tools

tating restretching. Also, the water may water the Also, restretching. tating

Finally, the level of drying of the of drying of level the Finally, On Tools: On

causing the stretcher to warp and necessi- and warp to stretcher the causing

Moving and Storage of Paintings: of Storage and Moving

advantage of it. of advantage limitations. Cotton canvas may shrink, may canvas Cotton limitations.

freezing is not advisable. not is freezing have developed techniques to take to techniques developed have hours with acrylics, but beware of some of beware but acrylics, with hours

will sustain several freeze-thaw cycles, freeze-thaw several sustain will fighting this characteristic, many artists many characteristic, this fighting you to paint in relatively thin glazes for glazes thin relatively in paint to you

not be frozen. Although most acrylic paints acrylic most Although frozen. be not rapid drying of acrylic paint. Instead of Instead paint. acrylic of drying rapid the paint moist. This technique will allow will technique This moist. paint the

quite well in most basements, but should but basements, most in well quite would not be possible without the very the without possible be not would membrane, allowing water through to keep to through water allowing membrane,

contaminating the paint. Paints will stay will Paints paint. the contaminating and quick manipulation of the surface the of manipulation quick and dried gesso acts as a semi-permeable a as acts gesso dried

spraying, use distilled water to avoid to water distilled use spraying, glazing techniques, hard-edged applications hard-edged techniques, glazing have now created a stay-wet canvas. The canvas. stay-wet a created now have

the paint to keep the paint fresh. When fresh. paint the keep to paint the almost immediately. The unique acrylic unique The immediately. almost or sponges to the back of the canvas. You canvas. the of back the to sponges or

spraying a small amount of water on top of top on water of amount small a spraying property, which allows for painting over painting for allows which property, canvas with water, and/or attach wet rags wet attach and/or water, with canvas

will begin to dry out. Some artists suggest artists Some out. dry to begin will come from people taking advantage of this of advantage taking people from come temporary stretcher. Soak the back of the of back the Soak stretcher. temporary

tops will not seal properly and the paints the and properly seal not will tops of the most successful uses of acrylic paint acrylic of uses successful most the of completely dry, attach the canvas to a to canvas the attach dry, completely

If paint accumulates on these surfaces the surfaces these on accumulates paint If acrylics can also be of great benefit. Many benefit. great of be also can acrylics gesso. After allowing the gesso layers to layers gesso the allowing After gesso.

critical to clean the threads of lids and jars. and lids of threads the clean to critical The naturally quick drying time of time drying quick naturally The capitalizes on the permeability of acrylic of permeability the on capitalizes

lose water up to ten times as fast. It is It fast. as times ten to up water lose cotton canvas. cotton Another technique to retard drying retard to technique Another

Some of the clearer plastic containers can containers plastic clearer the of Some the contaminants found in unwashed in found contaminants the paint

ene plastic that has very low permeability. low very has that plastic ene ally sensitive to water and does not contain not does and water to sensitive ally dramatically lengthen the wet time of the of time wet the lengthen dramatically

vapor to escape. Golden uses a polyethyl- a uses Golden escape. to vapor polyester canvas, which is not dimension- not is which canvas, polyester the surface at regular intervals will intervals regular at surface the

porous and allow a small amount of water of amount small a allow and porous scoured (washed) cotton canvas. Or use Or canvas. cotton (washed) scoured a very light spray setting. Spraying across Spraying setting. spray light very a

or heaters. All plastic containers are slightly are containers plastic All heaters. or will be minimized or eliminated by using by eliminated or minimized be will similar result is to use a plant mister set on set mister plant a use to is result similar

storage, be sure not to place it near blowers near it place to not sure be storage, noticeable discoloration. These problems These discoloration. noticeable the effect. A cheaper way to achieve a achieve to way cheaper A effect. the

To prevent paint from drying out in out drying from paint prevent To the paint film. In severe cases this causes this cases severe In film. paint the on the painting surface will maximize will surface painting the on

Keeping Paints Fresh: Paints Keeping

wash impurities out of the canvas and into and canvas the of out impurities wash Drying Acrylics... Acrylics... Drying Continued from page 5 page from Continued

Just Paint Bulk Rate GOLDEN Artist Colors, Inc. U.S. Postage Bell Road New Berlin, NY 13411 USA PAID Norwich, NY Address Correction Requested. Permit #82