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COVID-19 Alert

Curb side pick up only starting November 23rd (due to the increase in covid cases and for the safety of customers and employees). We are accepting orders via phone 403-527-8535, fax 403-527-7508 and at plainsman@telus.net. For more info click here.

Technical Tips Blog

Roasting Ravenscrag Slip instead of calcining

A bisque fired container of roasted Ravenscrap Slip powder

This is the Ravenscrag Slip I used to calcine at it 1850F (about 10lbs in a bisque vessel). I am now roasting it to 1000F instead, this produces a smoother powder, less gritty. To make sure the heat penetrates for this size vessel I hold it for 2 hours at 1000F. If your container is smaller you could do less time, if any black material remains inside, then do a longer soak on the next firing. It is not actually calcining, since not all crystal water is expelled, so we call it "roasting". Why do this? Ravenscrag Slip is a clay, it shrinks. If the percentage is high enough the glaze can crack on drying (especially when applied thickly). The roast does not shrink. The idea is to tune a mix of raw and roast Ravenscrag to achieve a compromise between dry hardness and low shrinkage. Technically, Ravenscrag losses 3% of its weight on roasting so I should use 3% less. But I often swap them gram-for-gram.

Context: GR10-A, GR6-A, Ravenscrag Slip, Sterile white vs. pure Ravenscrag Slip as a liner glaze at cone 10R, Calcination

Thursday 26th November 2020

A bucket of glaze smells totally rank! What to do?

A bucket of glaze slurry that smells really bad

In some places and climates this is more of a problem than in others. It is often not something that can just be ignored because the rheology of the slurry will likely be affected. Is there a magic chemical one can dump in to fix it? Not really. The subject of micro organisms in glaze slurries can be as complicated as you want to make it. This is because there are just so many different things that could be causing the stink. And there is no one chemical that treats them all. Even if there was, it's use would be focussed on prevention rather than fixing a problem. And, it would being its own issues, hazards and specific procedures. There are some simple things to know about dealing with micro organisms in glazes that should enable to you keep relatively free of this issue.

Context: Micro Organisms

Tuesday 24th November 2020

2020 Sample Board for Plainsman Cone 10R Bodies

2020 Sample Board for Plainsman Cone 10R Bodies

Coming to a dealer near you. Or on our website. Point your phone at any of the QRCodes to take you informational and instructional pages. A couple of glazed samples for each show how the body reacts to common recipes. And there are QRCodes at the bottom for recommended glaze bases. Of course, you can use commercial glazes, but be sure to test for glaze fit (so they do not craze or shiver) and for leaching. The data sheets for each of these can also be reached using a simple url (e.g. plainsmanclays.com/p700).

Tuesday 24th November 2020

Our base glazes plus opacifiers on a dark burning body at cone 6

Red burning clay tiles with opacified versions of G2926B, G2934, G1214Z

The body is Plainsman M390. These are commonly-used base glazes. The top one is an MgO matte, next down is a calcium matte. They react very differently to these additions. Notice also the difference when titanium dioxide is applied thickly. Tin oxide fires whiter than zircon (e.g. Zircopax). Each opacifier has issues. Tin is expensive. Titanium is difficult to mix into the slurry (screening required), not as white or opaque, variations in thickness produce more difference in results and it can turn blue. Zircon is more likely to cutlery mark, twice as much is required and it amplifies the color of any iron present.

Context: G1214Z, G2934Y, G2934, An incredible M390-compatible cone 6 red-burning casting body, Opacifier

Thursday 19th November 2020

These Saskatchewan farmers are growing their crops in M340!

Layers of sedimentary clay exposed in a hill at Big Muddy, Saskatchewan

These amazing hills near Big Muddy, Saskatchewan expose the sedimentary layers of the Whitemud formation (and others). The light-colored layer at the bottom is what Plainsman calls A3, it makes up about half of M340. But below ground is the 3B layer, the other half. The dark grey layers above the Whitemuds are what we call A2, a ball clay. Of course, top soil has accumulated on top of the clay to be able to grow plants. Although this is about 250km east of the Plainsman quarry at Eastend, Saskatchewan - the clay layers are remarkably similar. The clay resources in the area are truly astounding, not just in the quantity and quality but also in the magnificent landscape they define.

Context: Clay in "dinosaur country" of southern Saskatchewan, IXL Industries clay quarry near Ravenscrag, Saskatchewan in 1984., T.Rex Discovery Centre, Plainsman Clays

Thursday 19th November 2020

Clay in "dinosaur country" of southern Saskatchewan

White clay layers visible on the steep side of the valley wall

This is a "badlands" slope in the Frenchman river valley. The valley exposes the "Whitemud Formation" in many places (clearly visible here half way down on the left). Two surface mines of Plainsman Clays are nearby (over the top and down the other side), in a place where lower-lying rolling hills leave much less over-burden to remove. To the left of this is a former mine of I-XL brick. This is also the site of a mine for the former Medalta Potteries. These materials were laid down as marine sediments during the Cretaceous period. Below the Whitemuds are formations from the Jurassic period. The skeleton of the world's largest T-Rex, dubbed "Scotty", was found 50km east of here (in the layers just above the Whitemuds).

Context: Ravenscrag Slip is Born, Mother Nature's Porcelain - From a Cretaceous Dust Storm!, These Saskatchewan farmers are growing their crops in M340!, T.Rex Discovery Centre, Medalta Potteries, Medalta Stoneware, Plainsman Clays

Thursday 19th November 2020

200 Shimpo wheels arriving at Plainsman. Prepared to be certified.

Crates of potter's wheels waiting in our main warehouse

This is a November 2020 shipment of wheels from Nidec-Shimpo of Japan. Although a large company, making drive mechanisms for many types of heavy equipment, they apply their technology to potter's wheels as a matter of pride in a country that reveres pottery in its culture. We have opened every box to reveal the serial number. A certified inspector will check each and affix another sticker to assure they meet CSA Code SPE-1000 for electrical safety. This approval enables the sale of the equipment to public institutions. And it assures you that the equipment meets CSA electrical standards and is safe and insurable for use at home. Wheels like these can last a lifetime. These are very difficult to find for sale as used. Where they are, it is not uncommon to see them sold for more than what was paid new. Within a week we sold 90 of these!

Context: Plainsman Clays

Saturday 14th November 2020

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

The same clay body fits glazes at low temperature and is a stoneware at medium fire. How?

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.

Context: Nepheline Syenite, 3D Clay, Low Fire White Talc Casting Body Recipe

Friday 30th October 2020

An incredible M390-compatible cone 6 red-burning casting body

A red cone 6 thrown glazeless coffee mug with a cast handle

This mug was thrown. But the handle was cast from L4005D, the recommended recipe for an M390-compatible casting body. This is not a product you can buy, you have to mix it yourself, but we have plenty of instructions and pictures. The fired maturity of the two (fired shrinkage and porosity) matches very well. The casting process is superior for certain shapes and ware types. And now, with 3D printing, it is much easier to make many kinds of casting molds. This handle mold is made by pouring plaster into a 3D printed form. These are strong, the handle on this glazeless mug endured a couple of good taps with a hammer and stayed solid. With glaze, the strength would be much better. The body fires a little browner in color than M390. It would be redder if we included more iron oxide in the recipe, but that would gel the slurry and make it harder to work with. As a red-burning body, this one has better casting properties than any other we have used.

Context: Our base glazes plus opacifiers on a dark burning body at cone 6, A novel way to test glaze compression and glaze fit, Plainsman M390

Thursday 29th October 2020

Plainsman Warehouse 1 getting a new roof

Our main warehouse is actually a historic building in our city. It was part of the former Medicine Hat Potteries (1938-55) and then Hycroft China till 1989. We depend heavily on it to be able to maintain a large stock of bodies and materials. It needs a new roof, that is a big job on a building this size. The roof has multiple drain sites that feed to large pipe suspended inside, today was the day to test the new system.

Context: Plainsman Clays

Thursday 29th October 2020

Plainsman Clays, 702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535, FAX: 403-527-7508, Email: plainsman@telus.net