Monthly Tech-Tip from Tony HansenI will send practical posts like these (from thousands I maintain). No ads or tracking. We are troubleshooting the confirm email, for now you will be subscribed immediately (the first monthly email will provide one-click unsubscribe). BlogThe outside glaze has a fining agent that clears the bubble cloudsThis is a buff stoneware body, Plainsman M340. A L3954F black engobe was applied inside and upper outside at leather hard. The piece was fired at cone 6 using the PLC6DS schedule. The inside, totally clouded glaze is G2926B. Outside is GA6-B Alberta Slip amber transparent. Normally this inside glaze is crystal-clear on other bodies (and on this one without the black engobe). Clearly, the black stain in the engobe is generating tiny gas bubbles at the exact wrong time during the firing and the melt is unable to pass them. The outside glaze on on the same engobe, but the GA6-B glaze is demonstrating its ability to clear the micro-bubble clouding. It contains a lot of Alberta Slip, a material that is not finely ground like others. Particles across the range from 60-200 mesh are present, some of them appear to be acting as a fining agent to clear the bubbles. Context: Thick application clouds a.., Fining Agent, Clouding in Ceramic Glazes.. Wednesday 20th November 2024 Glow in the dark glazesWhile these are available as commercial products you may want to mix your own to get maximum flexibility in surface character and color intensity. The key is phosphorescent pigments added to a transparent base recipe. The pigments are often made from strontium aluminate doped with rare earth elements like europium and dysprosium. This ebay search reveals they are readily available (using the search 'strontium aluminate glow powder'). While expensive, they are much less so than materials like cobalt oxide or lithium carbonate. These pigments are known for their long-lasting glow compared to older zinc sulfide-based products. It would be best to start at low temperatures, cone 04-06. Consider trying the G1916Q glaze base recipe first (then G3879, if you can get the frit). The Q recipe is temperature, thermal expansion and gloss adjustable (using different frits and frit mixtures). A common starting point is 10-20% pigment by weight. Context: G1916Q Monday 18th November 2024 Gold decal on a gunmetal matte black glazeThis is a cone 6 porcelain mug with G2934 matte glaze (with 6% black stain added). We get this satin matte effect in our test kilns using the PLC6DS schedule. Larger kilns cool slower so this glaze turns out too matte in them, we deal with that by increasing the percentage of glossy base (this is a 15:85 blend of G2926B glossy and G2934 matte). The gold decal is from Sanbao Studio. On the left, it has just been applied, other than the glossy finish revealing its location, no gold design is visible. But, after the decal firing, using the MDDCL schedule, we get the result on the right. Context: Ceramic Decals Monday 18th November 2024 A cone 10R blood red - without copper but with riskThis is G1947U clear glaze with 8% Mason 6021 encapsulated red stain added. The body is P700, a Grolleg kaolin porcelain. The one on the right, having significantly reduced clouding within, has one tiny addition: 2% Zircopax. It is acting as a micro-bubble fining agent, producing a brighter color and smoother surface. But there is a possible problem: These stains are not recommended for use above 2300F. Even though the color is very good, cone 10 is just on the edge of the limit temperature, so suitability for food surfaces would require careful testing for leaching cadmium. Context: Mason 6021 Red Stain, G1947U, Mason Color Reference Guide.., Copper Red, Fining Agent Saturday 16th November 2024 Crawling glaze on the convex edges of sanitarywareSanitaryware glazes are high in zircon, thus a stiff glaze melt is a part of their very nature. That means glaze crawling is a part of their nature! And, preventing it is a major effort by producers. Crawling most commonly happens inside acute contour changes (that thicken the layer), but crawl points can even occur on relatively flat surfaces. However, this time it appears on the outside of an abrupt curve. Factors that can cause crawling can compound on corners. During drying, soluble salts and binders in the clay tend to concentrate at edges and corners - these can affect glaze laydown (especially its thickness and adhesion). The slip casting process favours the concentration of the finest clay particles at the mold face, but corners see the most surface disruption during cleaning and tooling at the leather hard stage (which can expose coarser particles below the surface). Glazes containing clay must shrink somewhat during drying, a corner like this will be the first place a crack appears (and thus a crawl), especially if adhesion is not as good. Context: Crawling on sanitary ware.., Crawling Tuesday 12th November 2024 A step to prevent cracking at handle-joins on thrown mugsDrying cracks are opportunistic, especially in highly plastic or fine-particled clays. They like to initiate inside sharp acute angles. The sharper the angle the greater the chance of crack. By doing this procedure before the clay gets too stiff (in the leather-hard stage) you will deny a crack a place to start. Of course, even drying is still important, the water content of a handle should now be allowed to get too far ahead of that of the main body of the mug at any time. In the pictures on the right, two tools are being used to compress and round the angle at which the handle meets the wall of the mug. Context: Worst case scenario for.., Drying Crack Monday 11th November 2024 Craft store selling traditional terra cotta ware in Mexico 2020This ware is used all over the city by street-side restaurants and food vendors. And routinely used in the house. It is all lead-glazed. That glaze does not craze and thus seals the otherwise porous surface against bacterial growth. They all know to handle it with care to minimize breakage. Surfaces and edges are rough, it is poorly finished but most people value the tradition enough to not even notice. Of course factory-made ware is much stronger and more functional, and cheaper. But at meals and occasions many seek opportunities to use this at the table and show it off to their friends. Context: Make pottery in Mexico.., Is Mexican Terra-cotta pottery.., Can terra cotta ware.., Terra Cotta, Lead in Ceramic Glazes.. Monday 11th November 2024 Crawling on sanitary ware. Laydown is the first suspect.This is glaze crawling and it underscores the need for attention to the details of all production parameters. This one small glaze defect makes this pedestal sink either a refire, a second or unsaleable. This is most common on abrupt surface contours but that is not the case here. The cause of this is likely several factors combining. The glaze is opaque white because it contains a high percentage of zircon opacifier. Zircon glazes tend to do exactly this so their successful use is doubly dependent on minimizing the percentage added and on attention to other details to compensate. This glaze has been applied thickly to ensure good coverage (thicker laydowns bring more crawling problems). The glaze is likely low in clay and thus the physical bond of the dried glaze layer depends on the binders being used, their percentages, the integrity of the way they were mixed in, and their shelf life. The ability of the glaze laydown to dry-bond with the body depends on the condition of the surface (e.g. water content, dry or bisque fired, smoothness, dustfreeness, quality of materials used in the body and integrity of body preparation, etc), the presence of surface contaminants (e.g. soluble salts) and the way in which it was applied and its thickness. The glaze melt's ability fire-bond and form an interface with the body that produces a smooth surface is dependent on its melt fluidity and ability to form an interface with the body. Context: Surface tension differences between.., Two transparents having opposite.., 5 tin oxide vs.., Crawling in G2934Y Zircopax.., Crawling glaze on the.., Glaze laydown, Tipping point Monday 11th November 2024 These were just lumps - but I gave them meaningThis clay is exceptional in multiple ways, it clay is from Flintoft, Saskatchewan. It holds together in lumps (center picture) but when broken its sandy nature becomes clearly visible. Other sandy clays in the area are similar but when water is added this one is different: It becomes plastic, plastic enough to form well (notice the texture of the plastic material in the closeup photo on the upper left). And it dries quickly with low shrinkage (the drying test disk upper right shows perfect performance). This combination of properties is what brick makers look for. No wonder that a clay similar to this nearby was used at the Claybank brick plant for 75 years. Context: Will soil testing help.., Claybank Brick Plant National.., Insight-Live com cloud-based ceramic.. Friday 8th November 2024 Ceramic tissue transfers: Good goat, better pigThese are whiteware mugs (Plainsman M370) with tissue transfer designs that were applied at the leather hard stage. The pieces were then dried, bisque firing, clear glazed and then fired to cone 6. Tissue transfers are sold online in a wide range of designs (in full color also). They can also be made at home by silk screening the appropriate type of ink onto the tissue paper (you can make your own ink using ceramic pigments). These overglaze transparent recipes are G2934 matte (left) and G2926B glossy (right). The matte glaze softens the edges of the design. The pig is a good demonstration of how crisp the edges of lines can be (once the application techniques are mastered). This method of decorating is far less expensive than decals. And does not require an extra firing. While the ink is somewhat powdery, it can be stabilized with spray starch if pieces need to be transported for firing. Context: An underglaze tissue transfer.., Ceramic Transfer Printing 144.., Buy tissue paper ceramic.., Sanbao Studio - Ceramic.., Inglaze High Temperature Transfers.., Catie Miller terra cotta.., Ceramic Transfer Friday 8th November 2024 | Contact MeUse the contact form at the bottom on almost all the pages on this site or let's have a together. Other ways to Support My WorkSubscribe to Insight-Live.com. It is about doing testing and development, not letting the information slip away. Starts at $15 for 6 months.
Login to your online account Chemistry plus physics. Maintain your recipes, test results, firing schedules, pictures, materials, projects, etc. Access your data from any connected device. Import desktop Insight data (and of other products). Group accounts for industry and education. Private accounts for potters. Get started. Download for Mac, PC, Linux Interactive glaze chemistry for the desktop. Free (no longer in development but still maintained, M1 Mac version now available). Download here or in the Files panel within your Insight-live.com account. What people have said about Digitalfire
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