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M332

Description

Mid-temperature, sandy, plastic, semi-vitreous, warm medium brown, native throwing body. M332 is made from seven different native clay materials and it is generally used for two reasons: its appealing warm red fired color at cone 5-6 and its combination of a sandy texture and high plasticity. M332 is attractive when used with glazes that absorb and highlight body iron and with ware that leaves some bare patches of clay showing. M332 has exceptionally high dry strength.

Process Properties

M332 has a highly plastic base with a sand complement to add texture. While it throws very well and generates sufficient slip, it can be 'grabby' during throwing with care to make sure pressure surfaces are not well lubricated. Once you learn how to throw it you will be amazed at what it can do.

Cautions: Because of the sand content it can develop splits during construction or throwing if water is allowed to sit on the surface at stress points (i.e. the outer belly of a thrown vase). In addition, when pulling handles, you must develop techniques to minimize splitting. It is best to keep sponging of leather hard or dry ware to a minimum as this tends to remove fine particles at the surface and expose the coarser ones (a problem on the lips of functional ware. M332 needs to be dried with care to avoid cracking. Turn open shapes over as soon as they will support themselves and cover ware with cloth and plastic (not just plastic) to even out any gradients in water content.

Firing

M332 fired bars from cone 4 to 8 oxidation (bottom to top).

M332 burns to a warm brick-red at cone 3-5, shifting to a medium variegated red brown at cone 6, and finally to a grey brown by cone 8. If you want the attractive red color remember that M332 undergoes a sudden color shift from red to brown between cone 6 and 7. Fire carefully to avoid overshooting the target temperature and losing the red. The redish color depends on the body firing to 4-5% porosity.

To get the best defect-free surface please consider using a hold-rise-drop-hold firing schedule. For cone 6 you could start with the PLC6DS schedule.

Glazing

Since we add materials with coarser particles and impurities to give the surface a more earthy appearance you can expect that the body will not provide perfectly clean glazed surfaces for functional ware. Glaze disruptions such as small pinholes and specks will be common. You can often solve this by using a drop-and-soak firing schedule. In other cases it may be necessary to fire the bisque a little higher to expel more gases of decomposition.

Although M332 burns a warm red color at cone 5, if you apply a transparent glaze it will flux the surface and the color will likely darken and turn dark brown brown. Thus, if you need to achieve red glazed colors it may be necessary to fire at cone 3-4. Also, because this is an iron-brown burning body it will impose some of its color on all glazes, darkening them and muddying colors.

Caution About Clear Glazes

Clear glazes often do not work on dark bodies. The center mug is clear-glazed with G2926B (and is full of bubble clouds). This dark body (M390) is exposed inside and out (the other two mugs have a white engobe inside and midway down the outside). G2926B is an early-melter (starting around cone 02) so it is susceptible to dark-burning bodies that generate more gases of decomposition. Left mug: The outside glaze adds 4% iron to G2926B (the glaze was not screened, so iron particles are agglomerated and acting as a fining agent, removing the bubbles). Right mug: The whole thing is glazed with GA6-A Alberta Slip base glaze (but using Ferro Frit 3195 instead of 3134). These amber glazes have an added benefit: The color darkens over dark burning bodies (to almost black).

Glaze Recipes

Commercial brush-on glazes offer many colors and surfaces. For functional ware check for glaze fit (vital for quality functional ware). Do not assume food safety of brightly colored glazes in your kiln and with layering without a leach test (e.g. GLLE test). Consider using transparent or white liner glazes for food surfaces.

Mixing your own glazes is practical (with our clear guidelines even beginners can make dipping glazes that go on silky smooth and evenly and dry in seconds). If you already do this using recipes from the web, be careful. High-feldspar glazes (having more than about 35%) often craze. Ones that rely on high melt fluidity to encourage crystallization and variegation (often because of excessive Gerstley Borate, lithium carbonate, zinc or Frit), view these with suspicion for leaching and cutlery marking; test them well (also test the additionless versions). Be suspicious of any glaze not having good documentation.

The best approach is to begin with a good transparent base you understand and that fits. We supply (as products and recipes) G2926B glossy whiteware and G2934 matte frit-fluxed bases. Their documentation describes how to mix, use, fire and adjust them and showcases stain, color and variegator additions to create an infinite number of effects. The former, G2926B, may not have a enough melt fluidity to create non-food-surface reactive visual effects with certain colors and variegators. G3806C fluid-melt recipe is an alternative (but check for crazing). These pages also reference other base glazes that might be of interest.

Consider also making glazes based on Alberta Slip (especially the GA6-A amber base) and Ravenscrag Slip. These materials have their own websites with lots of helpful information.

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.

This body is a great candidate for the engobe process, we recommend the L3954B recipe.

If you want to develop and mix your own glazes and engobes consider getting an account at http://insight-live.com. You can organize a methodical development program and adopt better methods of testing (e.g. melt fluidity, thermal stress, slip-fit tests).

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: 19.5-20.5%
 Drying Factor: c332
 Dry Density: n/a

Sieve Analysis (Tyler mesh):

     +48: 0.1-0.5%
   48-65: 2.0-4.0
  65-100: 6.5-9.5
 100-150: 6.0-8.0
 150-200: 8.0-11.0
 200-325: 8.0-12.0

Fired Shrinkage:

 Cone 4: 3.0-4.0%
 Cone 5: 3.5-4.5
 Cone 6: 4.0-5.0
 Cone 7: 4.5-5.5
 Cone 8: 5.0-6.0

Fired Absorption:

 Cone 4: 5.5-7.5%
 Cone 5: 4.5-6.0
 Cone 6: 3.5-4.5
 Cone 7: 2.5-3.5
 Cone 8: 1.5-2.5

Gallery

M332 bowl by Louise Bouchard.

Safety Data Sheet

Click here for web view.

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