L211

Description

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

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.

Glaze Recipes

If you wish to paint on glazes, many commercial brands are available. Use these in conjunction with under-glazes to create many effects. To get the best defect-free surface, use a drop-and-soak firing schedule (see link below). Unfortunately these may or may not fit.

If you wish to dip your ware to glaze it then commercial glazes may not be practical (they often dry very slowly and drip badly). The answer is a recipe. Mixing your own glaze from a pre-mixed powder you buy from us (or weighing out your own ingredients) is more economical. However at low temperature it is very difficult provide one-glaze-that-fits-for-everyone. But if circumstances are narrowed, it is practical. For example, we have found that for making functional ware the G2931B Zero3 variant fits this body at cone 03. That cone number is important. We do not trust electronic controllers to be accurate, we verify using cones and manually program to compensate for error (we recommend you do the same). If you need to fire lower or higher than 03 you might experience crazing. Technical info is available here). Another option is the G1916M recipe, it is highly expansion adjustable.

We recommend stress testing by boiling-water-into-ice-water (and vice versa) to bring out any crazing or shivering in your functional ware. If that happens, make changes and retest.

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

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