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Important Notice

Plainsman Clays Ltd. will be closed to public access starting Thursday March 19. We will keep the doors closed (no exceptions), but continue to take and fill orders via phone (credit card only accepted) and e-mail. Pick up orders will be placed at the front of the building, however we will be unable to assist with loading. These measures enable us to limit contact and minimize risk with regards to the COVID-19 virus.

We can be reached by phone at 403-527-8535, fax 403-527-7508 and via email at plainsman@telus.net.

Thank you for your understanding during this difficult time.

Trafficked online recipes waiting for a victim to try them!

A pile of printed recipes to try, but few are likely to work

You found some recipes. Their photos looked great, you bought $500 of materials to try them, but none worked! Why? Consider these recipes. Many have 50+% feldspar/Cornwall/nepheline (with little dolomite or talc to counteract their high thermal expansion, they will craze). Many are high in Gerstley Borate (it will turn the slurry into a bucket of jelly, cause crawling). Others waste high percentages of expensive tin, lithium and cobalt in crappy base recipes. Metal carbonates in some encourage blistering. Some melt too much and run onto the kiln shelf. Some contain almost no clay (they will settle like a rock in the bucket). A better way? Find, or develop, fritted, stable base transparent glossy and matte base recipes that fit your body, have good slurry properties, resist leaching and cutlery marking. Identify the mechanisms (colorants, opacifiers and variegators) in a recipe you want to try and transplant these into your own base (or mix of bases). And use stains for color (instead of metal oxides).

Context: Trafficking in Glaze Recipes, Metal leaching from ceramic glazes: Lab report example, Mechanism, Base Glaze, Limit Recipe, Glaze Recipes

Saturday 23rd May 2020

What we see in the park beside the Plainsman plant

The Plainsman Clays factory is right beside a baseball park. A beautiful place in the summer where children play and teams compete. But in the afternoon and evenings the deer move in. And mow the grass! The deer stay around all winter, in this residential area they are away from the coyotes and occasional mountain lion in the nearby river valleys.

Context: Plainsman Clays

Sunday 17th May 2020

Letterpress plates from BoxcarPress.com. Great for stamping designs.

Different depths are available, you need the 0.047 maximum relief depth (you can order a sample pack to try the various types they have). While shallower ones will make a crisp design into the clay, if you wish to put color into the recesses (at bisque stage) the shallow depth will make it difficult to avoid sponging it out when cleaning the high spots. Traditionally polymer plates have had metal backing and were expensive (and brittle). But these are flexible, inexpensive and easy to get online. When designing them create a border around the outside (when the stamp is pressed hard into the clay, the edges smear outward, that containment-line keeps edges clean). Also, the plates do not actually need to be stuck to a piece of wood, it is often better to lay them face down on the clay and use a wooden block and hammer to press them into the clay (which need to be quite stiff). Use spray cooking oil as a parting agent if needed.

Context: Example of a logo done using a polymer plate, Cone 6 stoneware coffee mug with a letterpress-made stamp, Boxcar Press website (for polymer plates)

Friday 15th May 2020

A drying box for smaller items of pottery enables something special

Freshly thrown porcelain mugs placed on a plaster table and being covered by a wax-lined box

These mugs are on a plaster table, just thrown on the wheel. I made the box cover from a large sheet of cardboard and painted wax emulsion on the inside. I drew a line on the plaster for its boundaries. When left overnight under the box the mugs dewater evenly, the plaster pulls water from the air in the box and directly from the thicker bases. In the morning they are stiff enough for handle attachment and to turn over on an arborite bat for a little more drying to ready them for trimming. An big advantage of this method is that I can throw ware minutes before closing time, come back in the morning, and they are ready. And they do not experience the unevenness in drying that normally happens when pieces are left to air dry (after throwing) until they are stiff enough to support a cloth and plastic to cover them.

Context: Drying Ceramics Without Cracks

Thursday 14th May 2020

Why throw on a plaster bat when making larger pieces?

A large thrown vessel, having dried overnight under plastic and on a plaster bat, is ready to turn o

To achieve more even drying. As soon as was practical after throwing (a few hours), I covered the piece with a cloth and then put a garbage bag over it. While that put the upper section a little ahead of the base in drying, over night the base caught up (the plaster sucks the water out of it, even the walls of the piece stiffen). In the morning I remove the plastic and within an hour or two it is ready to lift off the bat and turn over, shortly after that I can trim it. I secure each plaster bat to the wheel-head using a "Batmate", that works extremely well. To stick the clay to the plaster well I apply a thin layer of slip, round off the piece of clay and firmly slam it down onto the plaster (if it is not rounded it will not stick as well or may break the bat). This is quick and effective to achieve the even drying needed to avoid a drying crack. This method is especially important for large plates and bowls, which often suffer s-cracks.

Context: Drying Ceramics Without Cracks, Wanna throw porcelain plates with thick bottoms and thin rims?, Making your own plaster bats is easier than you might think, Plaster Bat

Monday 11th May 2020

Want bright orange? Use a stain in your own base transparent recipe.

Fired glaze tiles showing an orange promise, what actually came out and a better way

Orange is a very difficult color in ceramics. Inclusion stains are the only reliable method, they universally used in industry. But you could ignore that and try a bunch of recipes online. When they are presented on flashy web pages they can look tantalizing. But beware! Are the exotic materials you need to buy worth it. Will it actually fire orange? Will it craze or run or blister or leach or cutlery mark or crawl or settle like a rock in the bucket? It is much better to put an orange encapsulated stain into a transparent glaze you already know works on your clay. Then just experiment with percentage to get the color you want. Or, how about trying a premixed orange at low fire? Ware can be amazingly functional at low temperatures (e.g. cone 03-02) and bright colours labelled for cone 06 mostly work fine in that range.

Context: Trafficking in Glaze Recipes, Metal leaching from ceramic glazes: Lab report example, Encapsulated Stains

Thursday 7th May 2020

Melt fluidity differences are not obvious by just comparing glazed ware

The glaze on two porcelain mugs looks the same, but the melt flow is very different

These two Plainsman M370 mugs were fired at cone 6, the left one with G2934 matte glaze, the right one with G2934Y4 matte. They look and feel identical in the hand. The two glazes have the same chemistry. But they employ different materials to source that chemistry. The secret of of the matteness is high MgO (magnesia content). In the glaze on the left that MgO is sourced by dolomite, a lot of it. The glaze on the right sources it from a special frit, Ferro 3249. The impact of this difference is visible in the melt flows, the fritted one is obviously melting and flowing better. On other clays, especially stonewares, the G2934 can have a dry surface that cutlery marks. Thicker applications make it worse. But the Y version exhibits no such issues. Its mattness, durability, cleanability and hardness are so good that it is being used in floor tile.

Context: G2934Y, G2934Y variations for fired hardness, COE adjustment, etc, Melt Fluidity

Wednesday 6th May 2020

Two reasons why porcelain recipes need silica

A porcelain cup with serious crazing and base crack concentric to the center

This is 70% kaolin and 30% feldspar. Fired at cone 6 with glaze G2926B. The fired body has a nice porcelaneous surface. But, right out of the kiln, it crazes like this! The dense craze pattern indicates a very serious fit problem. The thermal expansion of the kaolin:feldspar mix is much too low. Adding 25% low-expansion silica will solve the problem. The other issue is with the flat particle shape of kaolin. The throwing process has lined up the predominant kaolin particles concentric to the centre. During drying, and especially firing, more shrinkage occurs across them than along them. All ten of the cups made cracked like this! The solution is adding a filler, one with rounded particles to separate the kaolin plates. Silica is perfect, using the same 25% addition. The grains act like aggregate in concrete, strengthening the matrix and separating the clay particles, forcing them to orient more randomly.

Context: Formulating a Porcelain, Porcelain

Wednesday 6th May 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 nearby.

Context: Ravenscrag Slip is Born, Mother Nature's Porcelain - From a Cretaceous Dust Storm!, Plainsman Clays

Monday 27th April 2020

A honey glaze that needs a base having more melt fludity

A pottery mug with a honey over-glaze that highlights an engobe having a decorative crack pattern

This transparent glaze adds a little manganese and iron, just enough to give color, but still maintain transparency to highlight the decorative crack-network in the engobe below. However this glaze is not as brilliant and transparent as it could be. As you can see in the surface reflections, it has an "orange peel" texture on the glass surface. This is due to a combination of factors (e.g. not enough melt fluidity, gassing of the manganese during melting, cooling the kiln too quickly). If the colorants were transplanted into a more fluid-melt transparent, this glaze could be improved. Photo courtesy of J. Decker.

Context: Fluid Melt Glazes

Sunday 26th April 2020

Find thousands more like the following: Use the search field at the top of the page at the Digitalfire Reference Library.

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