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L213

Low temperature, smooth, medium plastic, off white to white burning, refined high-talc earthenware for modelling or casting.

L213 is available in a pugged plastic version and as a casting slip (KT#1-4:Pioneer Slip). It is a mix of 50% Pioneer Talc, 50% KT#1-4 Ball Clay and a small amount of bentonite (the slip mix has an additional 5% calcium carbonate and does not have the added bentonite). This standard mix has been used in hobby ceramics for many years. It is both plastic for modelling yet easy to work with as a casting body. L213 is the best choice for people who intend to use commercial premixed glazes from companies like Duncan, Mayco, Spectrum, etc. and who need a white burning material.

Process Properties

L213 is very slick and smooth and throws and models well for forms of all shapes and sizes. However ball clay/talc mixes are best suited to casting bodies and bentonite must be added for plastic use. This is not without detrimental side effects. You may find that the material is more difficult to centre on the wheel if not wedged well. This body can be difficult to pug, it tends to extrude in a non-homogeneous matrix of different stiffnesses. We strive to maintain it a little softer to compensate.

You can make forms that combine plastic L213 elements with cast CDI:Pioneer slip mold-made elements. If you are working with the casting slip also consider using the deflocculated slurry to join sections since its much lower water content produces less shrinkage. However do not expect the same drying performance from L213; slip cast ware typically has much thinner and more uniform wall thicknesses than hand made ware. In addition, L213 has added bentonite to increase plasticity, this increases drying shrinkage and therefore drying cracks are more likely.

If you want to start casting it is very important to understand the deflocculation process and how to measure viscosity and specific gravity to maintain the slurry. There is a page on the Internet at http://digitalfire.com/magic/slip.htm that deals with this.

Firing

L213 burns very white from cone 06 to cone 2 due to the lack of a glassy phase that darkens iron and the use of special white burning ball clay and talc. As a result you can apply a transparent glaze and achieve clean looking ware and colored glazes fire to much brighter shades.

Above cone 2 the fired body color shifts to grey-buff and ware becomes unstable as it begins to vitrify. By cone 4 fired ware will be volatile (may bloat in one firing and be stable in the next).

The large amount of talc in L213 increases its thermal expansion (as you can see on the graph). This is a disadvantage if ware will be used for functional purposes requiring thermal shock resistance. However the contraction of the ware during cooling tends to squeeze the glaze onto the ware and prevents it from crazing.

Since L213 is 50% ball clay (which tends to block venting of water vapor) you must be careful not to fire too fast during early stages. We recommend preheating the kiln overnight to give the ware lots of chance to dry thoroughly.

Glazing

L213 is very fine particled and works well with commercial pre-mixed glazes with little chance of producing pinholes (L212 is also a talc body but does not fire as white). You will find there is an amazing variety of products from companies such as Duncan, Spectrum, Mayco.

Glaze Recipes

If you have chosen L213 for its whiteness and wish to develop your own colors and effects using our base glaze recipes, remember that you must be willing to test and retest, especially to match the fit so that crazing and shivering do not occur.

You can develop a compatible glossy or matte base for this body from our suggested starting point base recipes available on our Internet web site at http://digitalfire.com/education/glaze/cone06.htm. Information is given on how to fit the glaze to your body and how to customize it it for colors, opacity, speck, variegation, etc. For slip decoration, be careful to match drying and fired shrinkage of the slip with the body since low temperatures generate little glass to adhere the slip. Call Plainsman for complete slip and glaze formulation information.

Thermal Expansion

The chart shown was produced from a specimen fired once to cone 04 in the Plainsman lab and tested in an Orton dilatometer. By comparing this with the charts of other bodies you will note that this body has a very high thermal expansion. If you fire to a different temperature, employ different heatup or cooldown rates, or glaze-fire more than once the thermal expansion in your ware may be different than this chart indicates.

Thermal Expansion Chart
Average: 7.9

Chemical Analysis

 CaO       5.1
 K2O       0.5
 KNaO      0.1
 MgO      11.1
 Na2O      0.1
 TiO2      0.6
 Al2O3    15.1
 SiO2     53.9
 Fe2O3     0.9
 FeO       0.0
 LOI      12.5%

Plainsman Clays Ltd.
Box 1266, 702 Wood Street, Medicine Hat, Alberta T1A 7M9
Phone: 403-527-8535 FAX: 403-527-7508

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