L213

Description

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. Both are a 50:50 mix of AmTal Talc and KT#1-4 Ball Clay. Each has a 2.5% addition of calcium carbonate. This recipe is a standard that has been used in hobby ceramics across North America for many decades. The casting version of L213 adds 0.5% bentonite and the throwing one 3.5% bentonite. 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 thrown surface texture.

L213 is very slick and smooth and throws and models well for forms of all shapes and sizes. Few bodies of any type can match the plasticity and drying performance of a ball clay:talc mix. Many of our customers sculpt large forms using L213.

You can make forms that combine plastic L213 elements from formed and 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 formed ware.

Firing

L213 fired bars. Cone 04, 02, 2, 4 and 6 oxidation (bottom to top).

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 whiter burning ball clay and talc. As a result you can apply a transparent glaze (for cone 06-04) and achieve clean looking ware and colored glazes fire to much brighter shades.

Above cone 2 the fired body color shifts to grey-buff. Still, L213 can be fired much higher without bloating or melting (we have gone all the way to cone 10R), however please experiment in your circumstances to determine how high you can practically fire it.

The large amount of talc in L213 increases the thermal expansion of ware fired at cone 04-06 (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 squeezes the glaze onto the ware and prevents it from crazing, this advantage is considered to far outweigh any issues with thermal shock.

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. You will find there is an wide variety of products from companies such as Duncan, Spectrum, Mayco, AMACO.

The G2931F glaze above contains Ulexite, if you wish to make a glaze from materials you have try a starting recipe of Frit 3124 42.5%, Frit 3134 42.5%, EP Kaolin 15% and test to get the degree of melting needed. If the glaze melts too much, add 5% silica or increase the kaolin. If it is not melting enough reduce the kaolin. Stress test in boiling water and then ice water to bring out any crazing or shivering. Adjust the fit by increasing the amount of Frit 3134 if the glaze shivers or 3124 if it crazes. Once your transparent is working you can use it as a base to create other glazes by adding colorants, opacifiers, variegators and specking agents.

For slip decoration use commercial underglaze products. Then clear glaze over those.

Casting Recipe

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 here that deals with this.

In our lab we use the following recipe for testing (scale this up to the batch size that you need):

L213C dry   1500 g
Water        700 g
Darvan #7   8-10 g

Start with the minimum amount of Darvan and mix well.
This recipe should yield a conservative specific gravity of 1.74. We do not suggest adding any more water if it is not fluid enough. Instead add more Darvan to the maximum recommended.

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.

Physical Properties

 Drying Shrinkage: 6.0-7.0%
 Dry Strength: n/a
 Water Content: 21-22%
 Drying Factor: A000
 LOI: 11-12%
 Dry Density: n/a

Sieve Analysis (Tyler mesh):

  65-100: 0.1-0.2%
 100-150: 0.1-0.4
 150-200: 1.0-2.0

Fired Shrinkage:

  Cone 06: 1-2%
  Cone 04: 2-3%
  Cone 02: 2.5-3.5
   Cone 2: 2.5-3.5

Fired Absorption:

  Cone 06: 13-15%
  Cone 04: 11-13
  Cone 02: 9-11
   Cone 2: 8-10
   Cone 4: 9-11
   Cone 6: 10-13

Safety Data Sheet

Click here for web view (format adheres to Globally Harmonized System of Classification and Labelling of Chemicals - GHS)

Logo Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508
Email: plainsman@telus.net