• Materials for Ceramics

3D Clay

Alternate Names: Plainsman PR#3 D

Description: Silty tan burning, low plasticty, vitreous stoneware

Related Information

Ravenscrag Saskatchewan clays fired at cone 10R

Glazeless (top) and with glaze (bottom): A1 (bentonitic), A2 (ball clay), A3 (stoneware), 3B (porcelains), 3C (lignitic ball clay), 3D (silt). The bottom row has also shows soluble salts (SOLU test).

IXL Industries clay quarry near Ravenscrag, Saskatchewan in 1984.

Layers of the Whitemud Formation are being mined. The layer being extracted is a silty stoneware they referred to as the "D member" (equivalent to Plainsman 3D which is mined several miles to the east for use in pottery). Below the D they continued to mine a much whiter kaolinized sand of equal or more thickness. Above the D is a ball clay (equivalent to Plainsman A2). Above that is a light-burning stoneware (the combined layers that Plainsman extracts separately as A3 and 3B). A foot-thick layer of much harder volcanic ash is visible in the green overburden at the top. From these stoneware clays they extruded brick of exceptional quality, firing it as high as cone 10. Twenty years later the company reclaimed this land and today you would be unable to find where the quarry was located.

Mel Noble at Plainsman Clay's Ravenscrag, Saskatchewan quarry

Plainsman Clays extracts 6 different sedimentary clays from this quarry (Mel knows where the layers separate). The dried test bars on the right show them (top to bottom). The range of properties exhibited is astounding. The top-most layer is the most plastic and has the most iron concretion particles (used in our most speckled reduction bodies). The bottom one is the least plastic and most silty (the base for Ravenscrag Slip). The middle two are complete buff stonewares made by mother nature (e.g. M340 and H550). A2, the second one down, is a ball clay (similar to commercial products like OM#4, Bell). A2 is refractory and the base for Plainsman Fireclay. The second from the bottom fires the whitest and is the most refractory (it is the base for H441G).

How is it possible for the same body to work well at both cone 04 and 6!

Plainsman 3D! White cone 04 bodies are not vitreous and strong and neither is this. But it is plastic, smooth and fits common low fire glazes. How? 15% Nepheline Syenite (also 50% Plainsman 3D, 35% ball clay and 3% bentonite). The unmelted nepheline particles impose their higher thermal expansion on the fired ceramic. Spectrum 700 clear glaze does not craze and does not permit the entry of water (the mug is glazed across the bottom and fired on a stilt). The mug on the right is made from the same clay, it has been fired ten cones higher, cone 6! Here the nepheline is acting as a flux, producing a dense and very strong stoneware (with G2926B, GA6-B glazes). This is incredible! One note: This cannot be deflocculated and used for casting, soluble salts in the 3D gel the slurry.

GA6-C on a light and dark burning clay body at cone 6

Left: Plainsman 3D, a raw quarry material that fires as a buff stoneware at cone 6-8. Right: Plainsman Coffee clay (stained black using raw umber). Both were fired using the C6DHSC firing schedule. The inside glaze is the GA6-B Alberta Slip base. As of Dec/2021 cobalt retails at $100/500g! Yet the deep blue color on the mug on the right contains zero cobalt, the color is from titanium and iron. This GA6-C blue happens with any dark burning body, or with light burning ones having a dark engobe (e.g. L3954B with a dark colored stain) under the glaze.

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