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L210

Description

Low temperature, silty smooth, medium plastic, brown-burning, native terra cotta body. L210 is a low-talc low-fire terra cotta body that Plainsman has made for many years. Its main appeal has been to schools that like its light raw color since this is easier to clean up. L210 burns browner than our other low temperature reds. Because it is low in talc L210 may craze with some commercial glazes (however making your own glaze is easy and much less expensive).

Process Properties

L210 is a mix of one of our low fire red-burning fine grained plastic materials with a silty buff stoneware clay and 10% talc. It has medium plasticity and very slight texture. It is somewhat susceptible to water splitting so we recommend care not to use excessive water in pulling handles and throwing extreme shapes. Where joins with slip are made (i.e. handles), wipe away any excess that gets squeezed out during compression to avoid a split.

We do not recommend L210 for large sculptural ware since it lacks coarser particles and has a fairly high drying shrinkage. To avoid drying cracks use our recommended drying procedures. The most important of these is do what is necessary to make drying even throughout the piece. You can do this using a damp room or covering with a cloth and then plastic to slow down drying (the slow down helps even it out).

Firing

L210 fires to a light brown at cone 04-06. By cone 02 the color dramatically intensifies to a dense stoneware brown. By cone 4 it is over fired.

L210's warm color and strength in the cone 1-3 range make it a good candidate to produce low fire stoneware or vitreous tile. However be careful of warping if shapes are overhung too much.

Like any other low-fire body at cone 06-04, L210 is fairly weak and has high porosity. You might consider bisque firing higher (e.g. cone 03) to strengthen ware if you need to fire at 06-04 for your glaze. Please experiment since the increased density associated with higher bisquing can make it difficult to get the glaze to adhere and dry. Remember that L210 suddenly becomes very dense between 03 and 02 so your bisque firings need to be precise in this range.

L210 fired bars. Cone 06, 04, 02, 2 and 4 (bottom to top).

Glazing

Commercial brush-on glazes are formulated to fit high-talc bodies (like L213, L212). Talc bodies have high thermal expansion, this puts the squeeze on the glazes (reducing crazing). But this can go too far, glazes can be under excessive compression and shiver off contours or press outward from the inside of ware, cracking it (especially if ware is unglazed or engobed on the outside). We cannot guarantee that any glaze made by another manufacturer will not craze or shiver. Do stress testing (in boiling water:ice water, the BWIW test). Do not assume food safety of brightly colored glazes in your kiln without a leach test (e.g. GLLE test). Consider using transparent or white liner glazes for food surfaces.

Many find that commercial brushing and dipping glazes dry very slowly and drip badly. And they often do not fit well (craze or shiver). And they are expensive. With a little effort you can make your own of both types. And add stain and opacifier powders to make almost any color. There is no need to search for a recipe, we have done it for you. You can mix your own glaze from a pre-mixed powder you buy from us or weigh out your own ingredients. However, at low temperature, there is no one-glaze-that-fits-all bodies. To solve this we have created a three-recipe solution, these have thermal expansions that span the entire range of low fire bodies. And they fire crystal clear (in a drop-and-hold firing). Our Zero3 K transparent glaze fits low talc bodies (like L215) and low fire stoneware (like Zero3), Zero3 H fits high talc bodies (like L213, L212) and Zero3 L fits zero talc bodies (like Buffstone). We recommend cone 04-03 using a drop-and-hold firing schedule (for defect free surface and good transparency). Do not trust electronic controllers to be accurate, we verify using cones and manually program to compensate for error. If you need to fire lower or higher than 03, be sure and do testing first.

You can blend the K, H and L glazes to get the best fit. We recommend stress testing by boiling-water-into-ice-water (and vice versa) to bring out any crazing or shivering. If crazing occurs, blend in some of the L. If shivering occurs, blend in some of the H. In this way these glazes can be optimally fitted to almost any clay body.

It is also practical to make your own brushing glazes, ones that will work identically to the commercial ones mentioned above. Like the dipping versions, you can blend to tune the thermal expansion to fit your clay body. You will be surprised at how easy it is and how much money you can save.

Crazing: Functional ware must remain craze-free (crazing is unsanitary and drastically reduces ware strength). Because ware is not crazed out of the kiln does not mean it will not do so with time. Do cycles of a boiling water:ice water immersions (BWIW test) on a piece to test glaze fit (by stressing it to bring out any crazing or shivering tendencies).

Glaze slurry consistency and quality: A secret to achieving even glaze coverage is controlling the thixotropy and specific gravity of the slurry, both in freshly mixed and stored batches. A glaze of the right specific gravity and having a slightly gelled condition goes on to bisque ware evenly, does not drip and dries in seconds. Always screen glazes when first making them (80 mesh). Be alert to any particulate that may appear after storage (e.g. precipitates) and screen again if needed.

For slip decoration and engobes be careful to match the fired shrinkage of the slip with the body. Where we do not recommend a specific engobe recipe use a formula based on the porcelain itself. Add 2% VeeGum or Bentonite (the extra stickiness helps it adhere well to leather hard ware). Be careful about adding fluxes (e.g. frit), this increases fired shrinkage (the mismatch with body can cause flaking) and can compromise opacity.

L210 is also a candidate for use with cone 2 or 3 stoneware glazes. Keep in mind that transparent glazes may tend to darken the color of the clay more than you expect. For cone 2, increase the kaolin in the glaze to 30%. If the glaze is still melting too much add silica in 5% increments until it is right.

L210 has some coarser particles and thus can pinhole certain glazes. However by soaking the kiln (holding the temperature at top) these problems can be solved.

Thermal Expansion

We do not supply a thermal expansion value. The reason is that such numbers often mislead users. First, a body has different thermal expansion characteristics when fired at different temperatures, schedules and atmospheres. Dilatometers are only useful when manufacturers can measure bodies and glazes over time and in the same firing conditions. If a chart is supplied here, please view only as a way to compare one body with another.

Another significant issue is that many customers compare measured thermal expansion numbers with calculated values of glazes in efforts to fits those glazes to a body. This does not work. Calculated values are relative only and have limitations that must be understood. The best way to fit glazes to your clay bodies is by testing, evaluation, adjustment and retesting. For example, if a glaze crazes, adjust its recipe to bring the expansion down (using your account at insight-live), fire a glazed piece and thermal stress it (using an IWCT test, 300F into ice-water). If it still crazes, repeat the process.

If we recommend a base clear or glossy glaze, try calculating the expansion of that as a rough guide to know whether your glazes will fit.

Physical Properties

 Drying Shrinkage: 6.0-7.0%
 Dry Strength: n/a
 Water Content: 22.0-23.0%
 Drying Factor: C130
 Dry Density: n/a

Sieve Analysis (Tyler mesh):

     +35: 0.0-0.2%
   35-48: 0.5-1.0
   48-65: 0.5-1.0
  65-100: 1.0-3.0
 100-150: 2.0-4.0
 150-200: 5.0-8.0
 200-325: 10.0-13.0

Fired Shrinkage:

 Cone 06: 1.0-2.0%
 Cone 04: 2.0-3.0
 Cone 02: 6.0-7.0
  Cone 2: 7.0-8.0

Fired Absorption:

 Cone 06: 10-12%
 Cone 04: 8.0-10.0%
 Cone 02: 2.5-3.5
  Cone 2: 0.5-1.5

Safety Data Sheet

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We Are Rationalizing Our Product Line

Plainsman manufactures bodies by grinding and pugging clays that we mine (native bodies) and by batch mixing bagged minerals and materials that we import (refined bodies). We stock about 10,000 boxes of 50+ clays (some in multiple stiffnesses) and need to reduce the warehousing and production burden of small-run bodies and remove obsolete and legacy products. For bodies being discontinued: We have migration paths and can assist with issues. Some changes involve increased cost. In certain cases you might consider having us custom-mix a body so you can continue to get it, but please work with us on trying to adapt to alternatives first.

This product has issues

  • A legacy body recipe that predates newer and better materials.
Logo Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508
Email: plainsman@telus.net