An Analysis of Naturally Derived Marine Clay as a Ceramic Medium Julienne E. Beblo University of North Carolina Wilmington Faculty Mentor: Aaron Wilcox University of North Carolina Wilmington Abstract This project was conducted to evaluate the use of marine clay as a ceramic medium. Samples of the clay were collected from Kure Beach and analyzed using workability tests, mineralogi- cal analysis, and a chemical analysis. The clay shrank 15.63% after air drying and 17.75% after being fi red. Porosity was 26.0% and plasticity was identifi ed by handling the material. It contained 27.43% sand, 55.08% silt, 1.06% clay and also had high concentrations of aluminum and iron. Organic content was 15.79%. The marine clay did exhibit plasticity, was able to be thrown on a wheel and withstood fi ring. However, the small amount of actual clay present made the material more diffi cult to control and even after fi ring, it maintained a certain degree of fragility. The plasticity is likely a result of the high organic content. The clay is not ideal for functional studio work but it can perform as a ceramic medium. eramic clay has been widely used and those are defi ned, and what properties of the Cstudied for thousands of years. As a collected material infl uenced its usability in result, there is a comprehensive understand- the ceramic studio. The composition of the ing of the material and standards for evalu- collected material was analyzed and its func- ating its potential as a functional ceramic tionality was evaluated using existing stan- medium. But even as these standards are dards in ceramic studio practice. currently used, the fi eld continues to change as new processes are utilized and the materi- Defi nitions of Clay als are pushed to new extremes. In addition, much of the ceramic making process is still Clay is a naturally formed material derived determined by the preferences of the potter. from igneous rock. Interestingly, clay can The purpose of this project was to examine refer both to a particle size and to specifi c the use of naturally derived marine clay as compositions of natural materials. Any sedi- a ceramic medium. It predominantly en- mentary particle that is <2μm is considered compassed the production of creative pieces, clay. In addition, clay minerals are defi ned but with an emphasis on understanding the by their similar crystal structures and range characteristics of the collected clay, how of chemical compositions. Because of the 7 Explorations | Art and Humanities small particle sizes and chemical composi- clay similarly exhibits coarse particles and tion of clay minerals, the material exhibits organic-rich content. certain properties that have made it useful Marine and aquatic clays are also known in ceramics. Clay particles have a strong af- to create clay balls. These sedimentary for- fi nity for water and when the two substances mations occur when the fi ne particles of clay combine, the material swells. This helps the suspended in the liquid are rolled back and particles remain adhered to one another and forth due to wave and current action. The gives them the ability to retain a stable form particles naturally adhere to one another when wet. Kaolinite, for example, is a com- when water is present so the formation can mon clay mineral. It has a two-layered, hex- become signifi cant, forming lumps or balls of agonal shape with a diameter ranging from material. These formations will occasionally 0.3 μm-0.01 mm and a general thickness of roll up on shore and often exhibit relatively 0.05 μm. This particular structure has a high homogenous contents. surface area that is able to interact with water Generally, any kind of raw clay used in molecules. The interaction between water the studio can be categorized into fi ve dif- and clay particles actually gives the material ferent groups: china clay, ball clay, fi re clay, the characteristics that make it usable as a ce- stoneware clay, and surface clay. China clay ramic medium. is formed at the base of mountains and has A clay’s origin and whether it has been minimal impurities. It is rare, exhibits mini- transported from the spot in which it formed mal plasticity, and is also the most refractory, affect its properties. Clays that are found at or resistant to heat. Ball clay exhibits the their origin are considered “residual” while highest plasticity and has always been moved those that have been moved by natural by water from its primary spot of formation. forces-water, wind, erosion, etc.- to another This sedimentary clay has a fi ner particle size depositional area are considered “sedimen- that results in a high amount of shrinkage. tary.” Transportation of sedimentary clays Fire clay is found in mountain or desert areas increases the potential amount of impurities and has varying, coarse particle sizes. It is a present. This difference in composition may strong clay that has good standing strength change the plasticity and color of the ma- and is usually colored beige, red, gold, or terial. A high level of organic matter also red-brown when fi red. Stoneware exhibits tends to increase plasticity and occasionally properties similar to both ball and fi re clay. the stickiness of a clay. These characteristics make it a very work- Marine clays are likely the most common able material that also fi res to a high density. source of sedimentary clay. Generally, they Surface clay is the most prevalent. Because form when fi ne clay particles found in fresh- it has experienced years of movement, the water systems are deposited in brackish wa- level of impurities is high which increases ter. The clay particles absorb various impuri- the workability of the material. It tends to ties as they are transported from their place fi re a rust-red color, but this can change de- of origin by water movement. Marine clays, pending upon the presence of various metal- like most sedimentary clays, exhibit a higher lic oxides. Surface clay is also the material level of homogeneity and tend to have a high most commonly used by indigenous cultures percentage of organic content. They can be to create ceramic ware. grouped into three different categories based Raw clay exhibitis characteristics that are upon their location in various marine habitats. indicative of its origin and its qualities when Pelagic clay is found in deep water and tends wet. The creative process, however, usually to have very fi ne particles. Littoral clay is involves additional steps such as fi ring and found between the high and low watermarks glazing. Fired clay becomes ceramic ware of a shore and contains coarse particles with a and it exhibits specifi c properties that infl u- high percentage of organic matter. Estuarine ence its utility and its aesthetic. Ceramic 8 Julienne E. Beblo ware is generally categorized into three sepa- estimate the size at which the piece needs to rate groups. Earthenware is very porous and be created when wet so as to be the desired lightweight. It fi res at a low temperature size after being fi red and glazed. range and has commonly been used among Porosity refers to the percentage of empty tribal societies. It will absorb 10-15% of its space, called pores, found in the material. unglazed weight in water. Stoneware is a This characteristic is important because the very hard and durable clay that holds liquids number and size of pore spaces infl uence the and is not easily broken. It will absorb 2-5% hardness of the clay and its ability to vitrify. of its unglazed weight in water. Porcelain is Porosity can also be indicative of the type a dense and vitreous clay. It is known for of clay body being used. Porcelain clay has its generally white color and translucency. It 0-3% porosity while stoneware has 1-6% and will absorb 0-1% of its unglazed weight in earthenware has 4-10%. Measuring porosity water. Since the collected material was as- is diffi cult because some of the pore spaces sessed as a ceramic medium, understanding are sealed within the clay. To overcome this the categorization of clay and ceramic ware obstacle, testing the percentage of water ab- was necessary for describing the collected sorption is one of the most common meth- clay and for comparing it to other clays com- ods for testing porosity. This measures the monly used in the studio. amount of water absorbed by a bisque-fi red piece of clay. There are multiple procedures, Workability Defi nitions including some that require the bisque-fi red clay to be boiled for various time periods and The quality of clay used in the studio is a others that soak the clay overnight. somewhat ambiguous characteristic that can- Plasticity is an interesting characteristic of not always be easily identifi ed. Most often clay because there is no quantifi able measure- it is based upon a potter’s specifi c prefer- ment for it. Although potters will generally ence or upon the qualities needed to produce agree that plasticity is an important character- a particular piece of work. Even so, certain istic, it is predominantly determined by a pot- properties have been identifi ed that generally ter’s preference. Even so, there are multiple indicate the workability of clay when used in methods to determine if it is present. Simply a studio setting. Fortunately, most of those working with the clay to assess if it can with- have been given a quantifi able method of stand pressure, stretching, and a combination measurement.