High fire, sandy, semi-vitreous, grey burning, low plasticity speckled reduction stoneware.

H435 is a legacy body. It has been replaced by other better ones (H550, H450 which are smoother, more vitreous and lower in fired speckle) but some people still like it for its coarse and more earthy nature (it has about 15% fine sand and is quite high in silty stoneware clay). H435 is not vitreous.


This body is no longer available. The recipe contained 20% R-E sand and 20% 1D silt (that is why it had so much tooth on throwing). The other three ingredients are the same and about the same proportions as the new H550 we are making April 2023. The new mix of H550 is much better than the previous one we have been making (less prone to warping or bloating, more consistent, more plastic, smoother), it is now very similar to H450. Thus you could buy the sand and silt as dry materials and wedge them into H550 to make H435. They would wet very easily as a premix.

Process Properties

H435 feels quite sandy, especially during throwing. It contains a high-coal ball clay which imparts a dark grey color to the pugged material. Water can be absorbed during throwing making it susceptible to water-splitting (the sand provides openings into which water can penetrate). Thus it is beneficial to use water sparingly during throwing and make sure that it does not stay long on points of stress (i.e. the outside of the belly on a vase). Since H435 generates significant amounts of slip during throwing, try to develop a technique where the slip produced during centering can be employed later as a lubricant during throwing.


These fired test bars (left to to right) compare H431, H550 and H435 at cone 10R (top) and cone 11, 10, 9 and 8 oxidation.

H435 fires to a variegated speckled stone-grey color at cone 10R. It has more speckle than H550. In oxidation firing there is some very fine specks and the body retains a stoney light grey color through the cone 9-11 range.


H435 fits glazes well (it contains plenty of high-quartz clays). Glazes that craze on a porcelain body will usually fit well on H435.

H435 is quite dense in the bisque state compared to porcelains, thus it does not absorb water as fast or evenly. This may lead to pinholes forming as the glaze dries. We not bisquing this body any lower than cone 06 (because of the carbonaceous material that needs to be burned away).

Glaze Recipes

Commercial brush-on glazes: They may or may not fit our clays (check for glaze fit using a BWIW test or similar). For brightly colored glazes (especially with layering) do a leach test (e.g. GLLE test). Consider using a transparent or white liner glaze 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. Some recipes rely on high melt fluidity to encourage crystallization and variegation (often because of inadequate SiO2 and Al2O3 or containing Gerstley Borate 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.

Consider using our G1947U glossy or G2571A matte base recipes, just add colorants, opacifiers, variegators (you will find links to much more information and pictures about these). If you have a recipe that is troublesome, consider transplanting its opacifiers, colorants and variegators to these bases instead. and also have many recipes that work well on porcelains.

Crazing: Functional ware must remain craze-free (crazing is unsanitary and drastically reduces ware strength). Even though ware may not be crazed out-of-the kiln it may 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).

Thixotropy: If you want the best application properties for one-coat dipping, consider creating a thixotropic slurry. Thixotropic glazes are creamy because they have been thinned and then gelled by the addition of a flocculant.

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 one 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.

If you want to develop and mix your own glazes and engobes consider getting an account at 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 thermal expansion values. If a chart is supplied here, please view it only as a way to compare one body with another. Please note that, although you may calculate the thermal expansion of a glaze, this cannot be done for clay bodies since they do not melt. The best way to fit glazes to clay bodies is by testing, evaluation, adjustment and retesting. For example, if a glaze crazes, adjust its recipe to bring the expansion down, fire a glazed piece and thermal stress it (using an IWCT test, 300F into ice-water). If it still crazes, repeat the process.

Physical Properties

 Drying Shrinkage: 5.5-6.5%
 Dry Strength: n/a
 Water Content: 19.5-20.5%
 Drying Factor: c120-
 Dry Density: n/a

Sieve Analysis (Tyler mesh):

     +48: 0-0.5%
   48-65: 1.5-3.5
  65-100: 5.0-10.0
 100-150: 3.0-6.0
 150-200: 7.0-11.0
 200-325: 8.0-12.0

Fired Shrinkage:

   Cone 8: 3.5-4.5
  Cone 10: 4.5-5.5
 Cone 10R: 5.0-6.0

Fired Absorption:

   Cone 8: 5.5-6.5%
  Cone 10: 4.0-5.0
 Cone 10R: 4.0-5.0

Chemical Analysis

 BaO       0.5
 CaO       0.3
 K2O       2.1
 MgO       0.5
 Na2O      0.1
 TiO2      0.7
 Al2O3    17.4
 P2O5      0.0
 SiO2     69.4
 Fe2O3     1.3
 MnO       0.0
 LOI       7.8%

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