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A2 is a ball clay mined in a quarry about 5 km west of Ravenscrag, Sask. It has a very high plasticity and is suitable as an additive to all types of stoneware and earthenware bodies. This material is used in many bodies made by Plainsman Clays.
A2 has some intrinsic iron content which makes it burn cream-white. It also has some physical iron concretion particles which act as a source of specks and iron blossoms in reduction fired clay bodies employing it.
A2 has natural soluble salts that migrate to the surface during drying and leave a brown coloration on the buff-colored fired surface. However with 0.35% barium to solubles are removed. These soluble salts cause gelling during the deflocculation process and thus prevent A2 from being used in slip bodies.
Analysis updated July 97.
388 Ba ppm
34 Sr pmm
23 Y ppm
10 Sc ppm
413 Zr ppm
1 Be ppm
70 V ppm
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).
Plainsman 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).
Cone 10 reduction (top), cone 11 down to 8 oxidation below that.
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). 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 over burden at the top. From these stoneware clays they made 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.
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