Clay and dinosaur country in southern Saskatchewan
This is the Frenchman river valley and is the home of the "Whitemud Formation" and two of the mines of Plainsman Clays. The Whitemud layers are clearly visible on the badlands side of the valley (half way down on the left). However the Plainsman quarries are on the rolling hills side, where many places can be found having much less over-burden above the white layers. These materials were laid down as marine sediments during the Cretaceous period. Below the Whitemuds are formations from the Jurassic period. A complete T-Rex, dubbed "Scotty", was found nearby and can be seen in the T.rex Discovery Centre in Eastend, Saskatchewan.
Context: Ravenscrag Slip is Born
Friday 6th July 2018
Mining the Battle Formation in our quarry at Ravenscrag, Saskatchewan - June 2018
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.
Context: A1 Ball Clay
Friday 6th July 2018
Ever wondered why your dealer can quickly get the clay you need?
This is our warehouse. It is really big! There are 20,000+ boxes in stock of almost every kind of clay we make (about fifty). Plus a hundred different ceramic material powders, many of which we buy in truckload quantities. We keep all kinds of equipment and supplies in stock also (in other storage areas), having a total value exceeding that of the clay. This means that when your dealer orders a truckload of clay, materials, supplies, tools and equipment from us, they get it fast.
Wednesday 20th June 2018
Why is there a health warning on the top of each box of clay?
Like any dirt, clays contain quartz. Quartz particles, if inhaled in just the right size, can block the tiny air passages in your lungs. Quartz is all around us, it makes up about 12 percent of the land surface and about 20 percent of the Earth's crust. This label is a reminder to reduce dust levels in your studio and working area. You can see specifics about hazards of any of our products by clicking links (on any manfuacturers website) to view the SDS (Safety Data Sheet). It contains references to where you can learn more about working safely.
Context: Respirable Crystalline Silica
Wednesday 20th June 2018
Mel Noble at Plainsman Clay's Ravenscrag, Saskatchewan quarry
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).
Context: 3D Clay, 3C White Ball Clay, A2 Ball Clay, A1 Ball Clay, B Clay, A3 Stoneware Clay, Plainsman Clays, Secondary Clay
Wednesday 20th June 2018
What happens if Ravenscrag Raspberry is applied too thick
These are Plainsman P300 mugs fired at cone 6. When the glaze,
GR6-E, goes on too thick (as on the left) it is dark maroon and has a pebbly surface that does highlight contours. This went on too thick because the
specific gravity of the slurry was too high, about 1.53 (even a one-second dip put to thick a layer on the pieces). When I thinned it down to about 1.45 and flocculated it using espom salts, it went on thinner, yet still evenly, and I got the result on the right.
Context: GR6-E - Ravenscrag Cone 6 Raspberry Glossy, Specific gravity
Saturday 16th June 2018
Coffee Clay now available
Left: M390. Right: Coffee. The glaze is
GA6-A Alberta Slip amber base. The top halves have
L3954B white
engobe under the glaze. To read all about it on the Coffee Clay data sheet
click here. Its working properties are like M340. Glazes that work on M340 should work on this (e.g.
G2926B clear, Alberta Slip and Ravenscrag Slip glazes).
Colorants in the body will bleed into glazes, making them appear completely different than they would on lighter burning bodies. Rutile glazes will come alive! Most transparent glazes will bubble-cloud, use
GA6-A if possible (see the data sheet for more information).
Thursday 24th May 2018
Tune your matte glaze to the degree of matteness you want
G2934 is a popular matte for cone 6 (far left). It is not matte because it is not melting enough or is covered with micro-crystals, it is an MgO matte (a
mechanism produces a more pleasant surface that cutlery marks and stains less). But what if it is too matte for you? This recipe requires accurate firings, did your kiln really go to cone 6? Proven by a firing cone? If it did, then we need plan B: Add some glossy to shine it up a bit. I fired these ten-gram
GBMF test balls of glaze to cone 6 on porcelain tiles, they melted down into nice buttons that display the surface well. Top row proceeding right: 10%, 20%, 30%, 40%
G2926B added (100% far right). Bottom:
G2916F in the same proportions. The effects are similar but the top one produces a more pebbly surface.
Context: G2934 - Matte Glaze Base for Cone 6, G2916F - Cone 6 Stoneware/Whiteware Glossy Base Glaze, A good matte glaze. A bad matte glaze., A functional matte cone 6 glaze should melt as well as a glossy, Cutlery Marking, Glaze Recipes
Tuesday 22nd May 2018
Matte cone 6 glazes have identical chemistry but one melts more. Why?
These are 10 gram
GBMF test balls that we melted on porcelain tiles at cone 4 (top two) and cone 6 (bottom two). They compare the
melt fluidity of
G2934 (left) and
G2934Y (right). The Y version sources its MgO from
frit and talc (rather than dolomite). It is a much more fluid melt because the
frit is yielding the
oxides more readily. But Y has a key benefit: It has a much lower
LOI, producing fewer entrained air
bubbles and therefore fewer surface defects. And, even though it runs much more, it has the same matte surface! As long as it is applied at normal thickness, the extra
melt fluidity does not cause any running. And it has another benefit: Less cutlery marking issues. It is actually a very durable and practical food surface glaze, having a low
thermal expansion that fits almost any body. Although these appear glossy here, on ware they have the identical pleasant silky matte surface.
Context: Ferro Frit 3249, G2934Y - Cone 6 Magnesia Matte Low LOI Version, G2934 - Matte Glaze Base for Cone 6, G2934 vs. G2934Y cone 6 matte glaze, Matte Glaze, Dolomite Matte
Tuesday 22nd May 2018