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L211

Low to medium fire, smooth, medium plastic, buff burning, native material feldspar blend for earthenware or medium temperature stoneware.

L211 has been manufactured for many years. It is a mix of 1 part each of our two most consistent plastic stoneware clays along with two parts of a silty low plasticity stoneware material. In addition it contains 13% nepheline syenite to act as a flux to make it vitrify in the cone 6 range. The presence of the nepheline syenite offers no benefits for low temperature firing, it is a holdover from the past where this body served double duty for low and medium firing. While L211 continues to work well as a middle temperature stoneware it has been sold primarily as a low fire clay for many years. It is not as white burning as other members of our low temperature family but it is a balanced material offering robust drying properties that make it useful in school situations.

If you use L211 in the middle temperature range, we recommend that you also test M340. You might find that the latter is easier to work with or fires more to your liking.

Process Properties

L211 has a lower drying shrinkage and less plasticity than most other Plainsman bodies. This means that comparatively it has excellent drying properties however its lower plasticity make it suited to modelling or throwing of smaller forms. This behavior results from the fact that L211 is a mix of our smooth and plastic stoneware clays (used in bodies like M340) with an equal amount of our 3D silty clay. This produces a light and pleasant texture and a more open micro-structure that better vents water during drying. We recommend that you use our normal drying procedures for L211.

However there is one caution you must be aware of: The silty component makes the body susceptible to water splitting (water penetrating into the surface and beginning to split the clay during or shortly after forming, especially where the surface is being stretched). You should use minimum water during throwing and use slip rather than water as much as possible. Where slip is squeezed out of joins, be sure to sponge it away immediately. Splits caused by this are often misinterpreted as drying cracks.

Firing

L211 contrasts with talc bodies in that it is not volatile and thus restricted to use at low temperatures. L211 gradually matures and vitrifies over a wide range from cone 2 to about cone 8. When fired at cone 04-02, it is a yellow buff color and is porous like any other earthenware body. By cone 5 it is a greyish buff and by cone 7 it is stone grey.

L211 does not contain talc as most other buff earthenwares and thus it does not exhibit the higher expansions associated with talc bodies. This makes it more suitable for ware that will be exposed to thermal shock, but, it also makes it harder to fit glazes.

Glazing

L211 is not intended for use with commercial low fire hobby glazes, although there is a chance that certain ones might fit. We recommend ice water:boiling water testing to make sure.

L211 is ground to 42 mesh and although it has a natural fine grain, it is not as fine as bodies like L212 and M340. Thus you might find that some glazes will pinhole on the body. If this occurs, soak the firing, adjust the glaze recipe to give it a little more melt fluidity, or try L212 instead.

Glaze Recipes

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.

Physical Properties

 Drying Shrinkage: 4.5-5.5%
 Dry Strength: n/a
 Water Content: 19.5-20.5%
 Drying Factor: C120
 Dry Density: n/a

Sieve Analysis (Tyler mesh):

   48-65: 0.0-0.5%
  65-100: 1.0-2.5
 100-150: 1.5-3.5
 150-200: 3.5-5.5
 200-325: 8.0-11.0

Fired Shrinkage:

 Cone 04: 1.0-2.0%
 Cone 02: 2.5-3.5
  Cone 2: 3.0-4.0
  Cone 4: 4.0-5.0
  Cone 6: 5.5-6.5

Fired Absorption:

 Cone 04: 11.0-13.0%
 Cone 02: 8.0-10.0
  Cone 2: 6.0-8.0
  Cone 4: 4.0-6.0
  Cone 6: 1.0-2.0

Chemical Analysis

 BaO       0.6
 CaO       0.2
 K2O       2.7
 MgO       0.5
 Na2O      1.5
 TiO2      0.5
 Al2O3    17.7
 P2O5      0.0
 SiO2     69.0
 Fe2O3     1.1
 MnO       0.0
 LOI       6.1%

News

This body has been stable for many years, no recent changes have been made. However we are recommending other smoother and cleaner bodies such as buffstone and M340.

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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