• Materials for Ceramics

A3 Stoneware Clay

Description: Pr#3 A3, Buff Firing Stoneware Clay

Notes

A high-temperature, fairly clean (low in iron pyrite contamination) buff stoneware having ready-to-use plasticity for modelling and throwing. It is mined by Plainsman Clays at Ravenscrag, Sask. Many of their low, middle and high temperature buff burning clay bodies employ on this material. It is balanced and almost usuable as a cone 10 stoneware straight out of the ground. However, it has significant sand content.

357 Ba ppm
33 Sr pmm
24 Y ppm
14 Sc ppm
261 Zr ppm
2 Be ppm
82 V ppm

Related Information

Ravenscrag Saskatchewan clays fired at cone 10R

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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 A3 Native Stoneware fired test bars

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These are fired to cone 6, 8, 9 and 10 (top to bottom).

Physical properties for Plainsman A3

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This chart shows lab measurements and calculated results for drying shrinkage, fired shrinkage, absorption, drying factor, sieve analysdis, LOI and water content of plastic material.

Mel Noble at Plainsman Clay's Ravenscrag, Saskatchewan quarry

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Six different sedimentary clays are extracted from this quarry. It was opened in the 1970s, the best location available at the time. These test bars were made by slaking select lumps from each layer (thus exhibiting their best performance). The left-most dried test bars show the layers (top to bottom). The A1 top layer is the most plastic and has the most iron contamination (it is used in our most speckled reduction firing bodies). A2, the second one down, is a ball clay (similar to commercial products, although darker burning), it is very refractory and the base for Plainsman Fireclay. A3, third from top, is a complete buff high-temperature stoneware (like H550), although sandy and over-mature at cone 10. 3B, third from bottom, is a smooth medium-temperature stoneware; it contains significant natural feldspar (although fired color and particulate contamination are the most variable). The second from the bottom, 3C. fires the whitest and is the most refractory (it is the base for H441G). The bottom one, 3D, the best product in the quarry. Although the least plastic and most silty, it is also very fine particled and the cleanest (consistently free of particulate impurities and sand), it pairs very well with a ball clay to make a cone 6 stoneware.

Core sampling at a Plainsman quarry during summer 2021

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We are drilling test holes down through about 40 feet of overburden into the seven layers of clay to be mined. The rig assembles five-foot auger-sections, drilling down and pulling out two sections at-a-time. We examine the auger, identify the clays and record the results. At the middle of the auger-full shown you can see the division between the A2 ball clay and the A3 white stoneware, it was about 50 feet down. This hole was 80 feet, that spans tens of millions of years of sedimentation! This is the first time we have been able to sample the entire depth of the overburden, a highly plastic red burning low temperature clay, now we can assess whether it is a useful product.

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