Table of Contents Health & Safety 1 Clay 3 Kiln Firing & Operation 7 Underglazes 14 Glazes 17 Problems, Causes & Solutions 21 Glossary 26 Quick Reference Guide 33 A Word from Mayco... This booklet is designed to give you a general overview of the ceramics process. We have outlined the recommended use and application for products, but keep in mind that this is a guideline; often you can achieve successful results by breaking the rules.
Health & Safety Preparation, Application and Firing Ceramics is one of the most rewarding and enjoyable of all hobbies, and one of the safest, if some simple commonsense precautions are taken. As with any activity, responsibility must be taken for safe practices. General rules of good housekeeping and common sense should be applied when doing ceramics. Following simple rules will ensure your safety and help you produce great results when creating a ceramic project.
Health & Safety Labeling Information • Proper firing of dinnerware safe glazes is critical. Use shelf cones on the kiln shelves to ensure that the pieces are fired hot enough, even if the kiln is electronically controlled or has an automatic kiln sitter. Always fire in accordance with manufacturer’s instructions. If crazed or under fired, these glazes may not be food safe.
What is Clay? Clay & Clay Bodies Clay is a compound of minerals and organic material resulting from the natural decomposition of certain igneous rocks (for example, feldspar and granite are two common sources of clay minerals). As these mineral deposits age and get moved around by natural forces (wind, water, glaciers), chemical changes occur which cause the materials to become clay. The two major classes of naturally occurring clay deposits are primary clays and secondary clays.
Clay structure or binding material for the flux and glass-formers to bind together. The primary refractory material is alumina. Rather than add pure alumina high alumina clays, such as fire clay or kaolin, are blended into the clay body to increase the alumina content. better. Vitrification The process under which the clay body experiences chemical and physical changes during firing. The changes that take place during firing take place in stages.
Clay Classifications of Clay Bodies (calcium phosphate). The calcium reacts with silica to develop a very glassy material, giving the finished product the traditional translucent look. Two common methods of classifying clay bodies are according to the firing temperature range of the clay and by composition. Stoneware These clay bodies use natural stoneware clay and/or fireclay, with ball clay, kaolins, flint, fluxes and grog or sand as additives.
Clay Storing and Reprocessing Clay Unusual Ideas for Creating Texture It is necessary to store clay in a sealed plastic container. Purchase some large plastic bins. When doing a project you wish to return to later, store the project in the bins to keep them damp and organized by class. If the projects seem to dry out, damp paper towels or a damp sponge can be placed in the bin and will help keep projects moist. Teachers often have left over clay or inherit clay from a previous teacher or program.
All Fired Up . . . Kiln Firing and Operation Many kiln operators feel that opening the kiln after the firing is more exciting than Christmas morning. However, firing is as big of a responsibility as it is a pleasure. It is the most essential step the ceramist has in producing the finished “objets d'art.” Successful kiln firing requires knowledge and understanding of the equipment, what happens in the kiln during firing, and the various reactions of the different items and materials placed into the kiln.
Firing Guide Cone Firing Cone firing. Concurrently, a large shelf cone forced into the sitter would damage the mechanism. Guard Cone Kiln Sitter The W.P. Dawson Kiln Sitter is the control for the kiln and is the most widely used one today. There are newer types of kilns with computer controls that will be discussed later. We highly recommend installing a sitter on you kiln for it enables you to have more consistent firings with less chance of misfirings.
Firing View A mistakenly placed into the sitter. • A cone can become dislodged or allowed to come in contact with the porcelain tube. • Cones mishandled roughly, dropped or moistened will crack and bend too early. • The weight (hammer) of the sitter may not have engaged the claw when the cone is placed in it. • Something can get in the way and prevent the weight (hammer) from falling when the cone bends. View B Porcelain Tube Cone Supports Push Plunger in to activate kiln.
Firing independent and are often confused. Apply three thin coats (milk consistency) to the top of each kiln shelf with a large house brush. Allow to dry completely before firing. Kiln wash is not applied to the lid, sitter, elements, or the undersides of the shelves. Kiln wash will last many firings and it is not necessary to reapply unless the surface has flaked or has a lot of glaze build up on them. Simply scrape off any buildups of glaze with a putty knife.
Firing • Do not place the rims of large plates and bowls next to an element: this will heat the piece unevenly. • Flat pieces should be placed on shelves above the bottom two rows of elements for even firing. In this instance, it's better to use two half shelves, leaving a small 3/8” to 1/2” gap between them to promote better heat and air circulation. • Generally larger pieces go toward the top of the kiln. • Large volume pieces should be centered in the chamber with smaller pieces surrounding the ware.
Firing defects, as discussed above. Glazes that are labeled dinnerware safe are only dinnerware safe when the shelf cone stated in the instructions has been reached. Glazes that are underfired may appear cloudy or milky and lack the proper sheen to the surface. Sometimes glazes can be manipulated to accomplish a specific effect by firing to different temperatures. All glazed objects need to be stilted when possible, excluding stoneware and porcelain.
Firing Glaze Firing Many of the low fire glazes work on greenware (unfired) projects. Most all clear glazes work well, test others. These pieces need to be absolutely dry after glazing and fired like a bisque firing. The good news is you save one firing. The bad news is that if something explodes in a kiln, the exploded glazed piece sticks to other pieces. This can only be removed with a grinder or Dremel tool. If a teacher does not Cadmium reds can be have enough kiln very temperamental.
Putting Down a Foundation . . . Underglazes Sponging Opaque Underglazes Underglazes, originally, was a term used to refer to ceramic colors used under-the-glaze, like a foundation. The term has now become a general term and a specific material meaning. Generally the term refers to a product put on greenware that is covered with a clear glaze. This can be a translucent or opaque type of material. The translucent types are referred to as "One Strokes" and are usually covered with a glaze as well.
Underglazes thin applications that naturally result from ONE brush stroke. Very heavy applications of color can lead to problems of dry areas, cracking or bare spots where the One Strokes may pop off, taking the clear glaze with it. Bleeding of darker colors of blue and black may occur, but is generally the result of not firing the color before glazing or too heavy an application of the top clear glaze.
Underglazes Apply the desired glaze surface evenly with the proper amount of coats for the glaze. Thin the one strokes to the consistency of light cream or lighter. Two thin applications are better than one heavier one to produce the desired effect. Thickness of the color is very important for this technique. Translucent One Strokes and Opaque underglazes are interchangeable with most techniques. Creating patterns, banding, spattering and stippling can all be done equally well with either product.
This is Going to Come Out Green? Glazes brushes, bamboo and stain brushes should not be used for general glazing of a piece. The brush should be sized for the task that it is being used for; a small brush used to cover a large area will give unsatisfactory results. Do not use brushes previously used with stains. Glaze can be discolored by remaining traces of stains held in the brush. Condition of the raw glaze is as important as even application and the choice of brush.
Glazes If it is not dry, the brush may pick up the glaze, rather than put it down. If the glaze starts to shift or crawl while painting, then more drying time is needed. Crawling can also be caused by over fired bisque or bisque that has been sitting around too long, collecting a greasy film. Do not force faster drying with hair dryers; this can cause the glaze to perform badly. If a quicker drying time is needed, use indirect heat or a fan to dry the piece.
Glazes glossier the glaze is, the more it moves in the firing. Heavier applications of these glossier glazes will produce more dramatic intermingling of the colors. Not all glazes used in combination need to be so free moving. A non-moving glaze will retard the movement of a more active glaze. For example, applying three coats of a moving glaze on the bisque, then applying two coats of a non-moving glaze on top, the top glaze will break up into little islands of the matte color.
Glazes for food and drink. However, this may not be apparent until months later when the glaze has delayed crazing of the surface. All glazes should be from reputable manufacturers. They should have the proper seals from the ASTM guidelines for food containers. Remember that food safe glazes, when mixed together or applied one over the other, combine chemically and could produce a finish that is not food safe.
Oops, Now What Do I Do? Problems, Causes and Solutions From time to time there are problems that arise during the completion of a piece. This chapter is designed to help you quickly diagnose the problem, learn the cause and if possible, correct the mishap. The problems are listed in groups of categories. The problem may be listed more than once in slightly different ways to help you get to the solution. Glazes Problem Cause Solution Glaze crawls on inside vase.
Problems & Solutions Problem Pinholes in glaze. Cause Solution a. Primarily caused by underfired bisque. Can also be underfired glaze or a combination of the two firings. a. Fire bisque to shelf cone 04 or hotter and at a slower ramping temperature. Fire glaze to shelf cone 06. Ware needs a two cone difference in bisque and glaze firings. b. Try "Polishing" the dry glaze with the heel of your hand before firing. Sometimes pieces can be saved by reglazing and refiring. b. Improper glaze application.
Problems & Solutions Problem Reds fade in the firing, turning white to dark gray. Cause a. Glaze was applied too thinly. b. Insufficient ventilation in kiln during firing. c. Fired too hot or slow. Solution a. Reds need 4 coats of glaze. If this has happened to you before, start applying the extra coat before firing. Allow to dry completely between coats. b. Allow extra room around the piece in the kiln. Vent the kiln until the kiln has been turned or gone to high. c.
Problems & Solutions Problem Cause Solution Dipping glaze is too thick. Dipping glaze loses water with use through evaporation. Add small quantities of distilled water to glaze after dipping multiple pieces. Cover glaze when not in use. Smeared colors after firing. a. Colors not dry prior to dipping or brushing. b. Color dragged or disturbed while brushing clear glaze. a. Allow colors to dry completely before dipping or brushing. b. Remove excess water from brush before dipping in glaze.
Problems & Solutions Firing Problem Blisters, craters and pinholes in glaze. Cause a. Bubbles formed and glaze cooled too quickly. b. The glaze was fired on immature bisque. Reds develop darker spots in the color. a. Too heavy of application of color. b. Insufficient amount of oxygen for the glazes to develop during firing. Solution a. Allow kiln to cool slowly, soaking the kiln. (Turning the kiln back on low for 1 hour after the kiln has shut itself off.
What's in a Word . . . Glossary Binder - Gum Arabic used to make glazes adhere to the ware. Absorption - The ability of a porous object such as plaster or bisque, to absorb water; the amount of moisture that will soak into an item. Bisque - Ceramics that have been fired to the maturing point of the clay. Accenting - Emphasizing a portion of a design with highlights. A brighter color; outlining or partial outlining.
Glossary Dehydration - Loss of water through drying, evaporating or firing. Clay - Earth that is relatively pure alumina and silica; one of the material used in the manufacture of china and pottery. Density - Proportion of plaster to water; weight of any fluid as compared to the weight of water. Clay Carbon - Specially treated paper that will transfer a mark or pattern to a piece of ware. Clean-up Tool - Tool used to clean (fettle) the seams on greenware.
Glossary Glassification - Melting into a glass; i.e. Glaze. Extrude - To draw out; force or press out; force through a narrow opening, as clay. Glaze - A glass coating on a ceramic piece. Face - The outside surface of a mold. Glaze Butting - The specific placement of two glazes together so they do not run together. a.k.a. Controlled Glazing. Fat Oil - A china painting medium produced by the evaporation of gum turpentine. Glaze, Dipping - Type of glaze especially designed for a dipping process.
Glossary Lawn - To sift dry color through closely woven material. Hard Bisque - Term given to bisque that is fired to its hottest temperature before it goes liquid. Leach - To cause (a liquid) to filter down through some material; to extract a soluble substance from some material (as lead leached from glaze by an acidic liquid - i.e. orange or tomato juice). Harmonious - A color scheme chosen by some numerical sequence.
Glossary Plasticity - The pliability of modeling clay. Mold Cavity - The hollow section of a mold that is a negative of the finished casting. That part which is filled with slip to form the casting. Plug - A cone shaped section of refractory material used to close the peepholes in the kiln during firing. Mold Rubber - Liquid rubber used to make stamps of simple designs or master molds. Polish - To buff to a shine.
Glossary Release Time - Length of time needed before a casting can be removed from a mold. Shade - Any hue that has been deepened by the addition of black. See tints and tones. Relief - A raised design. Shelf Cone - Pyrometric cone used to tell the temperature at which the temperature on the shelf has been completed using heat work. The actual cone temperature. Renuzit - A dry cleaning material used to clean rubber stamps. Shelf Support - See Post.
Glossary Utilitarian Ware - Any object that will hold or contain food or liquid drink. Spray - To apply color by means of some type of air supply. Sprig - A clay trim, made in a press mold and attached to a leatherhard casting with mending slip. Vanishing Point - A point on the horizon line at which the lines of an object appear to converge; see perspective. Spur - A metal tripod used to stilt glazes ware during the firing.
Shelf cone 06 –10 Opaque after firing Buff or Gray in Color Normally white; can come in some colors Not Totally Vitreous Vitreous Stoneware Porcelain Shelf cone 2-10. Some industrial porcelains may reach cone 30.
2232 – shelf cone 6 350 Ramping Speed 2232 350 Ramping Speed 022 018 015 04 6-10 6-10 51/2-7 hrs. 31/2-4 hrs. 4-6 hrs. 8-10 hrs. 8-10 hrs. Glazes Lusters Greenware/ Earthenware Stoneware Porcelain 1940 350 Ramping Speed 1112 1323 1479 350 Ramping Speed 1830 with 350 Ramping speed 1940 with 350 Ramping Speed; Mid-range cone 6 2194 to 2232 04 to 6 Higher than 6 testing for color hold should be done. 06 – 6 6-8 hrs. for shelf cone 04 8-10 hrs.
Pg. 19 Pg. 22 Pg. 24 Non-toxic Non-moving when fired. Non-toxic Non-moving when fired. One Stroke™ Translucent Underglaze Non-toxic Astro Gem® Textural Glaze Non-moving when fired. Shelf cone 04-6. Check High Fire Guide for color changes at shelf cone 6. Shelf cone 04-6. Check High Fire Guide for color changes at shelf cone 6. Shelf cone 04-6. Check High Fire Guide for color changes at shelf cone 6.
Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Pg. 12 Pg. 13 Non-toxic Non-moving when fired. Non-toxic Non-moving when fired. Classic Crackles Crystalites Soft Fan Brush Brush/Sponge Brush/Sponge Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Pg. 14 Non-toxic Non-moving when fired. Elements Brush/Sponge Applied By: Shelf cone 06-6.
Pg. 11 Pg. 12 Pg. 25 Pg. 22 Non-toxic Non-moving when fired. Non-toxic Non-moving when fired. Non-toxic Dinnerware Safe Non-toxic Dinnerware Safe Dimensional Stroke & Coat® S-2000 Wonder Clear Dipping SC-209 Clearly-the-Best Dipping Shelf cone 06-6. Shelf cone 06-6. Shelf cone 06-6. Does not high fire; will flatten out Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Pg.
Soft Fan Brush Brush/Sponge/ Squeeze Bottle Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Shelf cone 06-6. Check High Fire Guide for color changes at shelf cone 6. Pg. 15 Pg. 16 Pottery Cascades Non-toxic Moves when fired Pottery Coat Non-toxic Non-moving when fired Applied By: Firing Range Health Status Mayco Book Product GLAZES: NON TOXIC 38 • Shake jar well before application.
Pg. 27 Pg. 32 Pg. 31 Pg. 33 Foodsafe glazes are marked with a star *symbol Not for Food Items Bisque Glazes Clear Art Glazes Not for Food Items Not for Food Items Art Glazes Exotic Glazes Mayco Book Health Status Product GLAZES: LEADED Shelf cone 06-6 Check High Fire Guide for color changes at shelf cone 6. Shelf cone 06-6 Check High Fire Guide for color changes at shelf cone 6. Shelf cone 06. Will not high fire cone 6 or higher.
Pg. 18 Pg. 25 Pg. 25 Pg. 25 C-210 Non-Toxic C-110 Food Safe Dinnerware Safe Dinnerware Safe Dinnerware Safe Roll-a-Coat Tintable Glaze C-100 Clear Dipping C-101 Blue White Clear Dipping C-109 Wonder Clear Dipping Pg. 26 Mayco Book Not for Food Items Health Status Jungle Gem™ Crystal Glazes Product GLAZES: LEADED Shelf cone 06-6 Shelf cone 06-6 Shelf cone 06-6 Shelf cone 06-6 Check High Fire Guide for color changes at shelf cone 6.
