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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.
Technical Tips Blog
Amaco underglazes can contain very high percentages of stain
Top are V-326 and V-388 underglazes, painted on and 04 bisque fired. Although the layer is very thin the coverage is amazing and the brightness is stunning. This degree of brilliance is not possible unless the percentage of stain is very high. That explains whey these are double or triple the cost of a typical commercial glaze. The bottom mugs are clear-glazed and 05 fired, the one on the left with Amaco LG-10 and the one of the right is Spectrum 700. The latter produces better results over the underglaze and is more transparent and less yellowish on the body.
Tuesday 18th January 2022
Making a QRCode using porcelain pixels
I 3D-printed a stamper to create 9mm square pixels. Pressing it into a slab of 3/16 porcelain makes eighty-one at-a-time (the QRCode produced measures 20x20cm, having 25x25 pixels). The black porcelain has 5% Mason 6666 stain. Firing temperature was cone 6. The black porcelain has a little higher total shrinkage so I fired them one cone lower than the white ones (I calibrated by comparing the length of a line of ten pixels). The pixels dry and shrink and drop out of the stamper easily. The action of the stamper rounds the upper corners of each. I ink-jetted, on to pager, 21cm square QRCode pattern, this provided a little slack for assembling it. Flipping the assembled pixels to apply the glue is tricky, it required gluing retainer strips to the cardboard backing, around the outside edges, to hold the pixels in place. For the next one I plan to glue the pixels to a zero-fired-shrinkage clay tile, made from L4410P. A little silicon sealant on the tile and that will be suitable outdoors. What does this QRCode say? https://plainsmanclays.com.
Monday 10th January 2022
You may know Veegum T but do you know VeeGum CER?
The glaze in this jar was 'goop', impossible to paint on because it was too viscous. And it dried way too fast. Laguna mentions adding water so I measured the specific gravity (SG): 1.7. That is super-high, it took a 125cc addition to bring it down to 1.5, but it was still thick, dried even faster and brushing it on evenly was even harder. It was not obvious what to do next. It needed a lot more water (1.3-1.35 SG is normal to support multi-layer application), adding CMC gum and enough water to do that would produce an unusable watery and sticky slurry. Veegum CER to the rescue! It is a 50:50 mix of CMC gum and Veegum T. The former slows drying and hardens, the latter gels. So it can simply be added until the painting properties are right. And, a Veegum CER solution is easier to handle than one of CMC gum. This really worked! The brushing properties are just right and it gels nicely on standing. CER is also good for highly fritted dipping glazes or others lacking in clay content (otherwise CMC might still be better).
Wednesday 5th January 2022
Improving a dipping glaze with a measured CMC addition
The problem: This dipping glaze is crawling (as shown on the glazed tile). Fortunately, the slurry has settled about an inch, that provides an opportunity for an immediate fix: Remove some of the water and replace it with gum solution. I want to replace about one tenth of the water (to be between a base coat dipping and brushing glaze). The bucket calculates to 2549g of powder so I need to remove 217g of water and replace it with gum solution. One way is to use a small sponge: Wet and wring it out and then repeat touching it to the water surface and wringing it out into a container until 217g. A propeller mixer is needed to mix in the added gum solution (it won't just stir in). Of course this degree of weight-precision may seen to be overkill, but having a record of what was actually done to adjust the slurry is important to repeating it the next time it is prepared or as a base for further adjustments.
Wednesday 5th January 2022
Common dipping glazes converted to jars of brushing glazes
These are cone 6 Alberta Slip recipes that have been brushed onto the outsides of these mugs (three coats). Recipes are GA6C Rutile Blue on the outside of the left mug, GA6F Alberta Slip Oatmeal on the outside of the center mug and GA6F Oatmeal over G2926B black on the outside of the right mug). One-pint jars were made using 500g of glaze powder, 75g of Laguna CMC gum solution (equivalent to 1 gram gum per 100 glaze powder) and 280g of water. Using a good mixer you can produce a silky smooth slurry of 1.6 specific gravity. However most commercial glazes do have a lower specific gravity (have more water), this does aid further in paintability but requires more coats. Amazingly, the presence of the gum also makes it unnecessary to calcine the Alberta Slip.
Wednesday 5th January 2022
Crawling in G2934Y zircon white glaze: There are simple fixes
G2934Y is a fabulous base glaze but it is not without issues. It has significant clay content in the recipe and high levels of Al2O3 in the chemistry, these make it susceptible to crawling. While it is normally fine as is, when you add certain stains to color it (especially at significant percentages) or opacify it using zircon (this has 10%), it can become more susceptible to crawling. On this mug, the glaze layer thickens at the recess of the handle join, that produces crawling during firing. Crawling can also happen on the insides of mugs, where wall and foot meet at a sharp angle. This happens, both because the glaze cracked here during drying and because the zircon stiffens the melt, making it less mobile. Adjusting the glaze recipe so it shrinks a little less on drying is an option (by trading some of the raw kaolin for calcined kaolin). But easier is to add a little CMC gum, start by letting it settle and replacing 10% of the water with gum solution.
Tuesday 4th January 2022
This serious glaze crawling problem was solved with a simple addition
This is G2934Y white (with 10% Zircopax). I initially blamed the zircon for the crawling. But, since the slurry had settled somewhat I was able to remove about 15% of the water and replace it with CMC gum solution. The gum addition was not enough to slow down the drying much (one reason to avoid gum if possible). That fixed it! Meaning that adherence of the dried layer to the smooth bisque was the issue. This being said, there were still a couple of small spots where it crawled. Replacing another 5% of the water should fix that. If you need to fix the problem with a gloss white it will likely require less gum, start with replacing 10% of the water.
Tuesday 4th January 2022
The G2934 glaze does not look good on dark-burning bodies
G2934 is a fantastic glaze, but only on the right body and with the right firing schedule. That is not the case here! This firing was done without any control on the cooling cycle. The added zircopax (to whiten it) stiffens the melt and makes G2934 pinhole-prone on dark burning bodies (because they generate more gases during heatup in the kiln). The clay on the right is Plainsman Coffee Clay, it contains 10% raw umber (a super-gasser). The centre one is Plainsman M390, it bubbles glazes more than buff-burning bodies. The left one is M332, it is a coarse grained and that seems to vent gases well enough here to eliminate the pinholes. The surface of the two on the right would be greatly improved using the C6DHSC firing schedule but, unfortunately, the slow cool would matte the glaze surface, making it really ugly. The PLC6DS drop-and-hold schedule might also reduce the pinholes, without matting the surface. What about without the zircon? There would be fewer pinholes, but micro-bubble clouding, which is not visible here because of the opacity, would make for a truly ugly effect on dark bodies.
Sunday 2nd January 2022
Gum does not work in a glaze if an important ingredient is missing
These brush-strokes of gummed glaze are painted onto an already-fired glaze (the gum enables adherence and drying without cracking). Notice brush strokes hold their character. The brown glaze on the left has 1.6 specific gravity (SG) and about 1.5% CMC gum. The white one has the same gum content but an SG of 1.5. It's brush stroke has flattened and it is running downward. This is not happening because of the lower SG, commercial glazes with an SG down to 1.3 can perform well. How? Because they also have Veegum to thicken them. That reveals thus secret: Gum needs particle surface area to work its magic. We can get that with a bentonite addition (it is fine particled like Veegum). The dried strokes on the right were much better, that glaze adds 2% bentonite. That made all the difference, it painted beautifully.
Thursday 16th December 2021
A moving response from a nurse in our Covid 19 ICU
In our small town of 60,000 we had 700 Covid cases at the height of the fourth wave. There were 80 workers in ICU at the time. They were under tremendous stress. Having doubled the normal capacity they were enduring fatigue, mistreatment, protests and misinformation campaigns. We made coffee mugs for all the workers. Pease read the response from one of the nurses.
Monday 13th December 2021
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