Hi John, I'm the glaze maker at a community studio and I've worked with GB in our glazes for years, until we switched to Laguna's gb blend, which worked fine, then to Gillespie (carnage) and back to GB blend (which was different the second time we bought it-acted more similar to Gillespie than before- my hypothesis is that Laguna is cutting the last of their GB with Gillespie in larger percentages of the latter until GB is gone.) Our glazes crawled with Gillespie ESPECIALLY when a Gillespie containing glaze was the first layer. Hypothesis: the ulexite is doing a crazy thing (reference digitalfire for photo) around 1400+ and knocking off the glaze layer above. Very slow firing (slower than kiln presets) fixed the crawling issues for glazes applied singularly, but NOT when layered. Not great in a community studio where people love to overlap, so I've had to replace many glazes to avoid gb (difficult). The only glaze that seems to behave, even with overlapping glaze, is, oddly PV base. Despite the large amount of gb. Must have to do with the large amount of clay in there too/the melt. This has been a summary of my twilight zone for the past several months, hope it helps. Julie Harbers
It would be interesting to measure the melting point temperature for each but I don't know how to do the on something that hot. For organics, we did it using a glass capillary tube attached to a mercury thermometer then heated it with a torch until it melted the measured the temperature. I imaging the capillary tube would work and a MAPP gas torch would get hot enough but a mercury thermometer won't go that high. Maybe you could do the same thing but use a Pyrometer rather then a thermometer. It would also be cool if you could measure the melt viscosity for each. I am very much a numbers guy.
Thanks John. Founds like a fun science experiment. Unfortunately I am a full time engineer, part time professor, and a "when I can find the time" potter. 😉
Hi John, I'm the glaze maker at a community studio and I've worked with GB in our glazes for years, until we switched to Laguna's gb blend, which worked fine, then to Gillespie (carnage) and back to GB blend (which was different the second time we bought it-acted more similar to Gillespie than before- my hypothesis is that Laguna is cutting the last of their GB with Gillespie in larger percentages of the latter until GB is gone.) Our glazes crawled with Gillespie ESPECIALLY when a Gillespie containing glaze was the first layer. Hypothesis: the ulexite is doing a crazy thing (reference digitalfire for photo) around 1400+ and knocking off the glaze layer above. Very slow firing (slower than kiln presets) fixed the crawling issues for glazes applied singularly, but NOT when layered. Not great in a community studio where people love to overlap, so I've had to replace many glazes to avoid gb (difficult). The only glaze that seems to behave, even with overlapping glaze, is, oddly PV base. Despite the large amount of gb. Must have to do with the large amount of clay in there too/the melt. This has been a summary of my twilight zone for the past several months, hope it helps. Julie Harbers
@@julharb thx so much for this post!!!
John, hope you are doing well and did not suffer damage from hurricane Helene.
It would be interesting to measure the melting point temperature for each but I don't know how to do the on something that hot.
For organics, we did it using a glass capillary tube attached to a mercury thermometer then heated it with a torch until it melted the measured the temperature.
I imaging the capillary tube would work and a MAPP gas torch would get hot enough but a mercury thermometer won't go that high.
Maybe you could do the same thing but use a Pyrometer rather then a thermometer.
It would also be cool if you could measure the melt viscosity for each.
I am very much a numbers guy.
Thanks John. Founds like a fun science experiment. Unfortunately I am a full time engineer, part time professor, and a "when I can find the time" potter. 😉
Thanks John! I’m wondering if the GB substitutes last longer in the glaze bucket. It’s probably too soon to know. Great video!
Good question!
Looks like someone was doing a spitting contest all that foam.
How to make contact with joh britt
What cone do you fire to for bisque?
@@CarisseH 04