In testing to determine the best specific gravity (SG) for this Darvan-deflocculated glaze slurry (G2926B), I arrived at what I thought would be great: 1.7. For 2.5kg of glaze powder only 1100g (1100ml) of water is needed, half the normal amount. And the slurry flows well. There appears to be enough water to form a good bond with the body. But a one-second dip of a bone dry piece produces twice the desired thickness, it dries too slowly and it is running. So, what should the SG be? I'll keep increasing the water until I can induce some thixotropy to hold it in place (using Epsom Salts), and it goes on thinner in a quick dip. If thixotropy is difficult, I’ll add 1% bentonite to increase particle surface area. And, I'll document the results at each step for future reference (in my Insight-Live account). Of course, these are going to need help drying, either by preheating the ware or putting the pieces in a drier.

This picture has its own page with more detail, click here to see it.
What issues to these carry? Glaze fit. Do these yourself and they might end up being glaze compression demonstration pieces. These are available on Aliexpress (as Drip Pottery, Drippy Pottery or Goopy Glazes) and they are made by a manufacturer that has close control of body maturity (and thus strength) and the capability to tune the thermal expansion fit of glaze-on-body. Glaze fit has to be better than normal because of the absence of an outside glaze on much of the surface. Too low an expansion and the compression (outward pressure) will fracture body (especially for thin-walled pieces). Too high and it will craze. And if the glaze is thick, it will shiver or craze with far less forgiveness than a thin layer. And how did they get the glaze on this thick? They likely deflocculate it, up to 1.7 or more, glaze the inside, let it dry, then glaze the outside. And apply the glaze to preheated ware. If done right, these pieces are a visual and technical achievement. However, drippy glazes in the hands of hobbyists carry more risk. They often just multiple layers of commercial brushing glaze that only by accident fits the body being used. No wonder their pieces often end up as time-bombs or crazed bacteria farms.
| Glossary |
Once-Fire
The practice of once-firing ceramics (no bisque) to produce fully glazed products. Considerable technical expertise and good testing are required to make it work. This is not a shortcut to skipping bisque firing. |
| Glossary |
Specific gravity
In ceramics, the specific gravity of slurries tells us their water-to-solids ratio. That ratio is a key indicator of performance and enabler of consistency. |
![]() PayPal | No tracking, No ads, No paywall, No transient content! Just organized, concise information constantly updated and improved. Was this helpful? Consider supporting me. |
Buy me a coffee and we can talk