Click the links to the left to get information and pricing on our products. Click the "Plainsman Data Sheets" for details information on the use and Plainsman clay bodies and glazes. The blog below is intended to help you with all manner of technical issues in ceramic hobby production, these posts come every few days, so check back often.
Both of the bodies are made from materials processed to minus 200 mesh. They were fired side-by-side to cone 6. Both bodies are vitreous, in fact, the buff burning one, Plainsman 3D 325, is more vitreous (the white one is Plainsman Polar Ice). The glaze is G2926B with 10% Mason 6304 stain and 2% Zircopax added. Clearly, iron content in the body heavily affects the development of the color in this glaze. But it is more. Because the 3D is highly vitreous the glaze melt is better able to leach iron from it.
As you can see from the search, this is becoming "a thing". The ash is being incorporated into both clay bodies and glazes. The ash of pets and humans. If you are a potter wondering about doing this here are a few tips. Do testing, better to use up some of the ash for that than have to throw away the ware you make! If the ash has not been ground (likely the case for pets) there will be bone fragments, these won't melt so need to be removed for glazes (by sieving or ball milling). For wedging into the body, testing will be needed (consider the possibility of lime-popping). Be careful to write down your procedure during testing so that production does not bring surprises. While you can add ash to commercial bottled glazes, the percentage will be low. If you make your own dipping glaze, 50% ash should be possible. Do tests without colorants to get a base glaze that is melting well and does not crawl. Add stain powders to test colors, zircon and titanium dioxide to opacify (the latter will variegate more). Color and opacifier additions can introduce crawling, test these well also.
Often the answer is yes. This glaze looks too matte, too metallic, too crystalline. This picture was sent to me by a worried person who had bought it and noticed it discolouring on the inside. The potter may very well have considered this safe just because it was fired to cone 10. It is common among potters to overload glazes with raw metal oxide blends, often 15% or more (e.g. manganese, copper, iron, nickel, cobalt). These percentages cannot be held in solution in the melt as it cools and solidifies, so they precipitate out and crystallize, especially if the glaze is not melting well or has insufficient SiO2. The crystalline forms of these metals might look nice to some people, but the glaze is likely to leach them. It is better to use a ceramic stain to create a black like this, adding it to a stable matte base glaze (one that melts well and has sufficient SiO2 and Al2O3 to create a durable glass). The concept of a limit recipe is helpful in eyeballing recipes for their likelihood of leaching.
Before jumping to conclusions consider all the factors that relate. This is M340S, it is fired at cone 6. That temperature is a "sweet spot" for this effect, high enough for the particles to bleed and low enough they do not bloat the body. Such bodies contain only about 0.2% of 60-80 mesh granular manganese (compare this to many glazes that employ 5% powdered manganese as a colorant). Further, the vast majority of the manganese particles are encapsulated within the clay matrix. The tiny percentage exposed at the body surface are under the glaze. It is not the manganese particles themselves that expose at the glaze surface. Rather particle surfaces that contact the underside of the glaze bleed out into it from below, doing so as a function the glaze thickness and melt fluidity. Thus, food contact with a glass surface having isolated manganese-pigmented regions is not at all the same thing as with raw manganese metal. Consider also that the total area of manganese-stained glass on a functional surface is extremely small for this effect.
Eastend, Saskatchewan hosts the incredible T. Rex Discovery Centre. The centre hosts Scotty, the world's largest T. Rex. The building is an architectural marvel and the exhibits are on par or better than anything else where. The building is actually embedded into the hillside in the same geological layers in which the fossilized skeleton was found, the Battle formation (just above the Whitemuds that are mined by Plainsman Clays). If you ever get a chance to drive from Ravenscrag to Eastend take the south road for the most dramatic views. Do it in the spring when the grass is green. The sheer scale of the valley, the land formations and the countless outcrops of the whitemuds will amaze. At Eastend, have a meal of Jack's Cafe, you won't be disappointed! Then go and see Scotty.
As this cone 6 melt flow test demonstrates, the Fusion F-12 is giving very similar performance to the Ferro. The GR6-A recipe is just 80% Ravenscrag Slip and 20% frit (10% zircopax has also been added to opacify). The degree-of-melt on the glazed tiles in also very similar, however notice that some of the whiteness has been lost on the second F-12 tile (the first is frit 3134). We are attributing this to the better melting of F-12, that is amplifying the color of iron present in the Ravenscrag Slip. For the third tile we reduced the frit to 15%, that has whitened it somewhat. Likely an increase in the zircon and would whiten it more.
After comparing the chemistries of an original feldspar and a tentative substitute, these melt flow tests are an excellent way to confirm physical similarity also. These were done at cone 6 (2200F). Each feldspar is mixed with 15% Ferro Frit 3195. Some things to note: Nepheline Syenite is the champion melter. Mahavir is very similar to G200. Kingman and Custer are very similar. Our Minspar substitute is very similar to Minspar itself.
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. These materials were laid down as marine sediments during the Cretaceous 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). Where are the layers of Scotties ancestors from the Jurassic period? Straight down until you hit the bed rock!
Context: Ravenscrag Slip is Born, Mother Nature's Porcelain - From a Cretaceous Dust Storm!, These Saskatchewan farmers are growing their crops in M340!, The world's largest T. Rex could have walked on our clay!, T.Rex Discovery Centre, Medalta Potteries, Plainsman Clays
In the spring this is what you will see to the north (near Ravenscrag on the south road to Eastend). The whitemud clays are clearly visible. The amount of overburden would be impossible to remove at this site, so Plainsman mines on the opposite side where gentle rolling hills fall to the valley bottom. But on the other side there are no outcrops, these white layers are largely hidden and can only be discovered by exploratory digging. But on this side they are easily accessed and can readily be sampled. This is the exact location where the whitemud clays were first discovered for pottery in the early 1900s, there are actually some mineable sections on the front hills to left. I-XL brick mined clay here for many years. This is also the site of a mine for the former Medalta Potteries.
This clay, L4115J3S, a Plainsman 3D-based experimental body, fires vitreous and dense (it contains 0.2% granular manganese). These glazes are very durable and functional. The outside glaze on both is G2934W (adds 10% zircopax). In our C6DHSC firings this produces as matte a surface as is possible without having excessive staining problems. Left mug inside glaze: An 85:15 mix of G2934 matte (without zircopax) and G2926B clear glossy. Right mug inside: G2926B clear glossy ball-milled, over this body it produces a striking visual surface. These mugs look as close to cone 10R dolomite-glazed ware as we have ever seen!