• Materials for Ceramics

A1 Ball Clay

Description: PR#3 A1, Pyritic bentonitic ball clay

Notes

A1 is mined by Plainsman Clays in southern Saskatchewan, Canada. It is at the top of the Whitemud formation just under or perhaps even part of the Battle formation. It is very high in iron stone concretions (pyrite) and soluble iron salts, a heavily stained bentonitic ball clay. While this would be considered a garbage material by most companies, artists and potters do not agree. It is useful in high-temperature reduction brown or dark burning pottery clay bodies to impart plasticity, iron speckle and variations in fired surface character. It usually is not used in amounts above 10%.

Related Information

Ravenscrag Saskatchewan clays fired at cone 10R

This picture has its own page with more detail, click here to see it.

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 A1 ball clay fired test bars

This picture has its own page with more detail, click here to see it.

Cone 10 reduction (top), 11 down to 9 oxidation below. The dark color is partly from iron bearing soluble salts that are left on the surface after drying.

Mining the Battle Formation in our quarry at Ravenscrag, Saskatchewan - June 2018

This picture has its own page with more detail, click here to see it.

This is the top layer. Battle clay is highly bentonitic, it is the "super hero of plasticity" in the quarry, it is unbelievably sticky. We have considered it "over-burden" in the past, but now will be looking for ways to employ Battle clay in our products and seeking special-purpose markets for it. Only 10% of this can turn a silt into a plastic throwing body! It is also high in fluxes (melts by cone 6). That means we can use it to improve the fired maturity of bodies, reducing the need for talc. Removal of this layer has exposed the top of the White-Mud Formation, the "A1" layer. A1 is employed in high fire bodies to impart brown color and fired speckle.

Mel Noble at Plainsman Clay's Ravenscrag, Saskatchewan quarry

This picture has its own page with more detail, click here to see it.

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.

Links

By Tony Hansen Follow me on

Got a Question?

Buy me a coffee and we can talk