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FIRING SUPPORT CENTER
Firing Unleaded Glazes

     Lead free or unleaded glazes are now the standard for commercial use. This is due to government regulations and health concerns by the manufacturers.
     As their name implies, lead free glazes are made from compositions or materials where lead has not been added.
     To eliminate lead, glazes are reformulated. This can change some of their properties. Some of the differences you might notice include:
1) glaze does not flow or run as much in firing as lead containing glazes.
2) brush marks may show after firing
3) not as wide a firing range
4) may not be as compatible with as many clay bodies. Can lead to shivering or crazing of the glaze.
5) color does not match lead glazes
6) more surface defects
     For problem-free results with lead free glazes, firings must be more closely controlled and well vented. Bodies may have to be bisque fired to a higher or lower cone number to solve problems.

     Lead softens glaze and allows it to be fired using several cone numbers. Glazes without lead have a narrower firing range. Example: A leaded glaze may be able to be fired anywhere from 05-08. Lead free glazes may only have a firing range of 05-06.

     Since the glaze and the clay body on which it is fired are made from different materials, it is important that they expand and shrink a like amount when heated and cooled. If they don't, then the fired glaze can be stretched to the point where it can crack, also called crazing. It can also be pushed together on to itself to a point where shivering or crawling occurs, sometimes revealing the bisque underneath.
When using lead free glazes:
1) Make test firings of the body and glaze to their recommended cone number, first the unglazed body and then the glazed bisque.
2) Use witness cones near the ware to be sure the proper cone number was reached. Differences may exist between the kiln-sitter and a witness cone or from the top to the bottom of the kiln. Firing with a controller to a cone number may also be inadequate.
3) If crazing occurs and the witness cone indicates the glaze and bisque firings are properly fired, make some tests by firing the bisque progressively hotter, to 03 instead of 04, for example. Also see out tips on carbon burnout.
4) If shivering occurs, fire one cone cooler. You may need to select another body for your bisque. Firing too cool is not a good idea since the strength is reduced and porosity increased, both of which can cause problems during the use of the piece.

If temperature in your kiln varies by more than 1-2 cones, then glazed ware in one part of your kiln may fire okay, while ware in another part may have a problem.
Be sure to read the tips page on firing uniformity.

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MASTER DISTRIBUTORS FOR:
Mayco Colors and Bisque
Duncan Colors and Bisque - I Love to Create
Paragon Kilns     Orton Vents & Cones
Skutt Kilns   Thomas Stuart Wheels
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Creative Paradise  Lehman Ceramic Equipment
Royal Brushes   Shimpo Ceramic Equipment
AMACO/Brent Color, Wheels and Slab Rollers

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American Ceramic Supply Company has been selling and servicing ceramic kilns to the ceramic industry, schools, individuals and studios for 40 years. Based in Fort Worth, Texas, American Ceramic Supply Company services and supplies ceramic equipment and supplies to traditional ceramic shops, paint your own pottery studios, ceramic potters, art teachers and art educators, ceramic and pottery finished ware producers, ceramic and pottery home based hobbyists. American Ceramic Supply Company provides education, training and consulting services to traditional ceramic shops, paint your own pottery studios, potters, art teachers and art educators, ceramic and pottery finished ware producers and home based hobbyists. American Ceramic Supply also educates and assists the architects, contractors, builders and electricians for our customers as they create their ceramic shops, paint your own pottery studios, ceramic rooms in their new schools and buildings and in their homes.

American Ceramic Supply Company and American Glass Supply Company sell ceramic kilns including Paragon Kilns, Skutt Kilns, Amaco/Excel Kilns, Cress Kilns and Olympic Kilns. Paragon’s Kilns include the Touch and Fire electric automatic kilns such as the TnF 82, TnF23, TnF24, TnF27 and TnF28’s, the Ovation kilns, Dragon and Super Dragon kilns, Iguana Kilns, Caldera and Clamshell Kilns, Janus kilns, as well as the small kilns such as the SC series kilns, heat treating kilns, doll and porcelain kilns. Skutt kilns include the Kiln Master kiln series - the popular KM818, KM1018, KM1027, KM1218, KM1227-3 and KM1231 kilns, the Glass Master kiln line such as the GM814, GM1014, GM1214 - the very popular GM1414 coffin kiln, and the production glass kiln line - the GM818, GM1018 and the GM1227-3 as well as the Skutt Hot Start Pro Kiln and the new Firebox kilns - Firebox 8 and Firebox 14 including the clamshell kiln GM22. Through American Ceramic Supply Company, Olympic Kilns has fantastic gas and glass kilns, raku kilns, electric - manual and automatic kilns such as the Dual Media Kilns, the Champ kiln, the Freedom Series kilns, the Commercial Electric kilns, and the Torchbearer Gas kilns- both available as propane or natural gas kilns. Olympic also has truck kilns, commercial industrial kilns, custom kilns, DPF Cleaning Kilns and industrial kilns. Amaco kilns and Excel Kilns are very popular kilns with teachers and art educators. Front loading kilns, top-loading kilns, professional kiln line series, Fine Art kilns, Professional Kiln series, and metal enameling kilns are all part of the Amaco kilns and Excel kilns production series. Whether you need a pottery kiln, jewelry kiln, silver art clay kiln, glass fusing kiln, glass slumping kiln, knife heat treating kiln, clay tile production kiln, low fire kiln, high fire kiln, 120V kiln, 240V kiln, 208V kiln or even a 480V kiln! -
American Ceramic Supply Company can provide you with just the kiln for your very special needs and desires to last you for a very long time!

American Ceramic Supply Company continues to sell, service, educate and provide on-going marketing and technical support to the ceramic and pottery industry. Our goals are the best customer service we can possibly offer, generosity of information to our customers so that they can succeed and accomplish their ceramic dreams and desires and
doing the right thing by God and Country.

American Ceramic Supply Company, Inc. - est. 1975
American Glass Supply Co.
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