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Stunning black silky matte glaze at cone 6

Stunning black silky matte glaze at cone 6

This contains 6% Mason 6666 gunmetal black stain. The base recipe, G2934, is an excellent balanced-chemistry host for a wide range of stains to produce equally stunning reds, yellows, oranges, etc. The fritted version of the recipe, G2934Y, provides an even better host. This glaze is affected by the clay it is on. The body on the right is highly vitreous, this has produced a finer texture that glistens in the light. The body on the left is a whiteware having 1% porosity (Plainsman M370). Firing schedule is also a factor, slower cooling will dull the color more. We use the PLC6DS firing schedule.

Monday 13th August 2018

DO NOT leave outsides of functional ware unglazed

DO NOT leave outsides of functional ware unglazed

This mug is made from the strongest porcelain I have, it is so vitreous that the bare fired surface does not even coffee-stain. So I glazed it only on the inside. That created a time-bomb waiting for hot coffee! Three others did exactly the same. Four other mugs glazed on the outside were fine. Why? Glaze compression (the inside glaze is pushing outward) is important to avoid crazing. But, when suddenly heated it pushes harder. Outside surface imperfections, even microscopic in size, provide crack-initiation-points to relieve the stress (the solution is an inside glaze with carefully tuned thermal expansion or an outside glaze to counter the forces and fill in all the imperfections).

Monday 6th August 2018

Mother Nature's Porcelain - From a Cretaceous Dust Storm!

Mother Nature's Porcelain - From a Cretaceous Dust Storm!

Plainsman Clays did 6 weeks of mining in June-July 2018 in Ravenscrag, Saskatchewan. We extracted marine sediment layers of the late Cretaceous period. The center portion of the B layer is so fine that it must have wind-transported (impossibly smooth, like a body that is pure terrasig)! The feldspar and silica are built-in, producing the glassiest surface I have ever seen (despite this, pieces are not warping in the firings at cone 6). I have not glazed the outside of this mug for demo purposes (a practice sure to fail in a crack when hot coffee is poured in).

Monday 6th August 2018

Humbled by Clive Tucker

Humbled by Clive Tucker

Clive Tucker and me (Tony Hansen) had a throw-off today. I got beat. I have never had to face a thrower as capable as this! He made the higher mug (on the right, we had 520 grams of clay each). It is a privilege to have, not just talented and artistic customers like this, but also technically capable ones like him. The real winner is the M370 clay we used. Even though it was too soft, neither of us had issues with twisting, it wanted to compete as much as we did.

Saturday 4th August 2018

Clay and dinosaur country in southern Saskatchewan

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.

Friday 6th July 2018

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

Friday 6th July 2018

Ever wondered why your dealer can quickly get the clay you need?

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?

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.

Wednesday 20th June 2018

Mel Noble at Plainsman Clay's Ravenscrag, Saskatchewan quarry

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).

Wednesday 20th June 2018

G2926S low expansion cone 6 base glaze is here

G2926S low expansion cone 6 base glaze is here

G2926B has proven to be my most durable, crystal clear, non-crazing, easy-to-use general purpose cone 6 base glaze (from dozens I developed). However, some porcelains (e.g. Plainsman P300) need an even lower thermal expansion. G2926S adjusts "B" (by adding low-expansion MgO at the expense of high-expansion KNaO). Yet it has the same gloss. The insides of these P300 mugs use it (with 10% added Zircopax to make white). "S" is not an all-purpose recipe, it could shiver on high silica bodies, use it if G2926B fails an IWCT test for crazing. These mugs were fired using the PLC6DS firing schedule, the outside glazes are G2934Y silky matte with added stains.

Saturday 16th June 2018

What happens if Ravenscrag Raspberry is applied too thick

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.

Saturday 16th June 2018

Coffee Clay now available

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

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.

Tuesday 22nd May 2018

Matte cone 6 glazes have identical chemistry but one melts more. Why?

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.

Tuesday 22nd May 2018

Match calculated COE to dilatometer-measured body COE? No!

Match calculated COE to dilatometer-measured body COE? No!

Why? Firing temperature, schedule and atmosphere affect the result. Dilatometers are only useful when manufacturers monitor bodies AND glazes over time and in the same firing conditions. Calculated values for glazes are only relative (not absolute). The best way to fit glazes to your clay bodies is by testing, evaluation, adjustment and retesting. For example, if a glaze crazes, adjust its recipe to bring the expansion down (your account at Insight-live has the tools and guides to do this). Then fire a glazed piece and thermal stress it (300F-to-ice-water IWCT test). If it still crazes, move it further. If you have a base glossy glaze that fits (and made of the same materials), try comparing its calculated expansion as a guide. Can you calculate body expansion from oxide chemistry? Definitely not, because bodies do not melt.

Tuesday 22nd May 2018

Roasting Ravenscrag Slip instead of calcining

Roasting Ravenscrag Slip instead of calcining

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. I hold it for 2 hours at 1000F to make sure the heat penetrates. 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.

Sunday 20th May 2018

Laguna B-Mix on Steroids! I have wedged in 10% and 20% Plainsman FireRed

Laguna B-Mix on Steroids! I have wedged in 10% and 20% Plainsman FireRed

Both pieces have a transparent glaze, G1947U. FireRed (the bar in the front) is a mix of A1 and St. Rose Red, both having heavy ironstone concretions. BMix has some specks anyway, this adds thousands creating some awesome aesthetics. This addition does not affect the working properties of BMix, it still throws very well. An added benefit is that pieces dry better. Fired strength and maturity are minimally affected (porosity stays around 1%). With a 20% addition the surface of the unglazed clay is almost metallic. Silky matte glazes, like G2571A, are stunning on a body like this.

Saturday 19th May 2018

The right amount of opacity highlights the incised design

The right amount of opacity highlights the incised design

The mug on the left is a commercial brushing glaze. The mechanism of this effect is that the glaze is much thinner on the edges of the design, thin enough that its opacity is mostly lost. The potter is attempting to mix her own equivalent (center and right). Her glaze adds 4% tin oxide to a transparent. However, as you can see, she has added too much. Further testing using lower percentages will find the right balance between the opacity needed to cover the brown body on the flat areas and the transparency needed to expose it on the contours.

Friday 18th May 2018

Better to mix your own cover glazes for production?

Better to mix your own cover glazes for production?

Yes. In this case the entire outside and inside of the mug need an evenly applied coat of glaze. In production, it would not make sense to attempt this by painting. For these reasons: Cost, quality, convenience. The right pail has 2 gallons of G2934Y base with 10% Cerdec yellow stain: $135. Cost of jars with the same amount: Almost $300! And you have to paint them on in three coats with drying in between. The one in the pail is a true dipping glaze (unlike dipping glazes sold by glaze manufacturers that dry slowly and drip-drip-drip just like brushing ones). This one dries immediately after dipping in a perfectly even layer (if mixed according to our instructions). And a bonus: This pail can be converted to a brushing version using CMC gum.

Tuesday 15th May 2018

Think the idea of mixing your own glazes is dead? Nope!

Think the idea of mixing your own glazes is dead? Nope!

These are two pallets (of three) that went on a semi-trailer load to a Plainsman Clays store in Edmonton this week. They are packed with hundreds of bags of powders used to mix glazes. More and more orders for raw ceramic materials are coming in all the time. Maybe you are using lots of bottled glazes but for your cover and liner glazes it is better to mix your own. And cheaper! And there are lots of recipes and premixed powders here to do it. One of the big advantages is that when you dip ware into a properly mixed slurry it goes on perfectly even, does not run and dries on the bisque in seconds. No bottled glaze can do that.

Sunday 13th May 2018