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L215

Description

Low temperature, smooth, plastic, red-burning, native, talc-containing terra cotta body. L215 is intended for use with the commercial glazes available from Duncan, Mayco, Spectrum, and similar companies. It achieves fit to these glazes with the use of only 10% talc in the recipe. L215 is made from natural red-firing terra cotta clays that melt at low temperatures, thus it develops better fired strength than more refractory white burning low fire bodies.

Process Properties

L215 is a mix of our M2 native clay, talc and ball clay. Plasticity, and therefore throwing performance, are excellent.

Firing

L215 Fired Bars (cone 4, 2, 02, 04, 06 top to bottom)

This material fires to a light red at cone 04-06 and the color intensifies to a brick red by cone 02. Further temperature increase shifts toward deep red, then brown, until it reaches its maximum strength and dark brown color around cone 1. The body becomes volatile above this range. Furthermore, like many terra cotta bodies, the color evolution is much more rapid from cone 02-1. Thus, ware fired in this range without good firing control will be subject to wide variations in color with comparatively small changes in firing temperature. Also, although the fired body may appear stable against warping at cone 03-02, do not overestimate its ability to withstand warping on extremely overhung shapes (e.g. bowls with flared flat rims).

Terra cotta bodies are weak and porous at cone 06. It is better to fire to cone 04-03, almost any low fire glaze will work fine there also.

Glazing

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. Of course, we cannot guarantee that any glaze made by another manufacturer will frit.

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 Zero3 K 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 Zero3 G glaze is a variant of the above, it has a much lower thermal expansion but is not as glossy and ultra-clear (technical info is available here). By blending some of that into the the K 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: 5.0-6.0%
 Dry Strength: n/a
 Water Content: 19-20.5%
 Drying Factor: C110-C120
 Dry Density: 1.98

Sieve Analysis (Tyler mesh):

     +48: 0.5-1.0%
   48-65: 2.0-5.0
  65-100: 5.0-9.0
 100-150: 4.0-7.0
 150-200: 3.5-6.0
 200-325: 8.0-12.0

Fired Shrinkage:

 Cone 04: 1.5-2.5%
 Cone 02: 4.5-5.5
  Cone 2: 6.0-7.5

Fired Absorption:

 Cone 04: 8.0-10.0%
 Cone 02: 3.5-5.5
  Cone 2: 1.0-2.0

Gallery

L215 with underglaze decoration and G2931K clear glaze. Fired at cone 03 in 3 hours cold-to-cold.

Safety Data Sheet

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