L212

Description

Low temperature, smooth, medium plastic, light cream to grey buff burning, refined talc earthenware. L212 is a mix of our cleanest native stoneware clays with 33% added talc. It is intended for good fit with commercial bottled glazes (i.e. Duncan, Mayco, Spectrum) and is a popular body for use in schools.

Process Properties

We have added a little ball clay and bentonite to improve and control the plasticity of L212 while it still retains the unique working properties and dry strength common to bodies in its family (H550, M340, Buffstone). Like classic ball clay:talc ceramic mixtures, this body has a unique and very pleasant smooth feel for throwing and modelling forms of all shapes and sizes.

L212 dries fairly quickly with minimal cracking. However it is fine grained so joins should be made using low water content slip and applying as much pressure and lateral movement as possible.

Firing

L212 bars fired at cone 04, 02, 2, 4 and 6 (bottom to top).

Although this body does not burn as white as L213 it is less expensive for us to manufacture. It fires best at cone 06-04. The color darkens to a yellow buff by cone 2, then to a grey buff by cone 4 and above. If you want to produce denser stronger ware you might consider firing L212 to cone 02 or higher. However we recommend you do this with caution because bodies of this type tend to melt suddenly. Although L212 might appear OK at cone 4, ware tends to be brittle at this temperature. Also, the volatility is not consistent; that is, L213 will melt at different temperatures for different runs.

Since L212 contains a significant amount of talc, it has a unique firing behavior. The talc significantly increases the thermal expansion of the ware. This is a disadvantage if ware will be used for functional purposes since it will not have as good thermal shock resistance. However the advantage is that contraction during cooling squeezes the glaze onto the ware and helps prevents it from crazing.

L213 is not made from white burning ball clay and talc as are typical ceramic slips. Thus it does not burn nearly as white.

It is important to realize that talc bodies of this type do not vitrify at cone 06-04. A typical thinly cast or thrown shape can often be torn apart with your bare hands.

Since L212 contains bentonite you must be careful not to fire too fast during early stages. Ball clay is very plastic and fine and thus does not vent water vapor quickly during the water smoking period of firing. We recommend that you candle the kiln overnight to give the ware a chance to dry thoroughly before starting the firing the next morning.

Glazing

L212 underglaze decorated mug with clear G2931K clear glaze. Fired at cone 03.

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 G2931K Zero3 transparent glaze fits this body well 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. The G2931B glaze is a variant of the above, it has a lower thermal expansion but is not as glossy and ultra-clear (technical info is available here). By blending some of that into the G2931K you will be able to develop a glaze that fits for you. 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.

To get the best defect-free surface please consider using a drop-and-soak firing schedule (you can find more information about it on this page).

Physical Properties

 Drying Shrinkage: 6.0-7.0%
 Dry Strength: n/a
 Water Content: 21.5-23.0%
 Drying Factor: C120
 Dry Density: 1.96

Sieve Analysis (Tyler mesh):

     +65: 0.1-0.5%
  65-100: 0.5-1.5
 100-150: 1.0-2.0
 150-200: 1.0-2.0
 200-325: 6.0-10.0

Fired Shrinkage:

 Cone 04: 1.5-2.5%
 Cone 02: 3.0-4.0
  Cone 2: 4.0-5.0

Fired Absorption:

 Cone 04: 11.0-14.0%
 Cone 02: 9.0-12.0
  Cone 2: 5.0-7.0

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