What Glaze Recipes Can Tell You

Welcome to The Potter’s Round Table, the topic today is What Glaze Recipes Can Tell You.

Want to get some idea of what a glaze might be like before you make it up? Glaze names and titles do not always accurately and completely describe the glazes. Once you have learned a little about common glaze ingredients, you can look at glaze recipes and often find clues about how the glazes will perform. This discussion reviews the three categories of glaze ingredients (fluxes, stabilizers, and glass-formers) and their various influences on glaze properties, and how we can predict some glaze properties by examining over twenty glaze recipes.

The Potters’ Round Table is a production of Washington Street Studios. As a result of the pandemic the Round Table is hosted as a YouTube livestream event and then edited to be added to our video library.

At Washington Street Studios, we believe the sharing of creative energy and knowledge will improve the quality of our art and increase the appreciation of art within our community. We are striving to create an environment where the arts are shared and appreciated. We want to grow as a family of artists and contribute to our community.

[krissader]

Just found you all. These videos are amazing. I am beginning a pottery journey. Retiring from 25 years as a fine art printmaker and teacher of. These are filling me in on so much. Thankyou.

[universegurl]

I just found this channel after returning to pottery after an 8 year break. I am taking it all in. Thanks for creating this content! Phil was a genius! Very engaging. I'm sorry to hear that he passed away! My condolences!

[WashingtonStreetStudios]

We received the following question via email: Throughout the video you discuss fluxes which melt at different temperatures. How does this affect the impact of substituting ingredients in a glaze? For example, what if I wanted to remove Gerstley borate from a recipe and replace it with Ferro Frit 3134. By adjusting the percentage of the other ingredients in the glaze, I could match the original chemical components, i.e. sodium, potassium, calcium, etc. But now I would be sourcing the boron from a frit rather than the Gerstley borate. I assume that this would affect the melting temperature and final result.

And Phil's response: Thanks for your question. There shouldn't be much difference if Gerstley borate is replaced by Ferro 3134; they both melt at bisque temperatures. The frit might melt a little more uniformly and faster than the Gerstley (because of the impurities), but at a moderately slow firing speed, I don't think that you would see much difference. This wouldn't be true for other substitutions where there was a big difference in the melting/fluxing temperatures, such as between whiting and a calcium frit. As long as the substitutions provide the proper chemical compositions, there shouldn't be a difference in the final results of proper firings, but the differences in melting temperatures can show up in the way that the glazes can interact with other glazes (overlaps) or in the optimum firing schedules required.

Phil

[fntkm]

Very informative, thank you so so so much.

[denniscaffrey]

Excellent teacher, worthy of a national foundation or fellowship

[joseeugeniofariaalvim]

I love and learning very much with your videos here in Brazil. Thank you millions.😊😊😊😊😊

[vicfowler]

I love your videos. Thank you for sharing such detailed information. As a newbie to the world of ceramics I am taking my first step into glaze mixing. Many of the recipes available online and in books provide ingredients in % or grams. I plan on only mixing small batches. Is there a method of determining total dry material weight for a quart batch?

[michirhythm]

I just found your page and love it. Could you please do a presentation about low fire glazes ... I am interested in making 04 and 06 glazes to use when I bisque fire! :). I use a gas kiln and am looking at cost effective glazes for mugs.

Thanks so much.

[Compastian]

Thank you for this great video. When talking about Whiting, he says it's calcium carbonate, which I'd learned, but then he says it's calcium oxide. What's the difference?

[annaponomareva]

Thank you again for the great video!! I noticed that in some of the presented recipes, bentonite is stated as additive although it's a clay and can work as stabilizer if I'm not mistaken. Just wonder why it is in the additive then? Also, I wonder how to test matte glazes for food safety?

[Felikeramik]

Thank you, great video. Does it means Zinc or Boron is necessary to get a 6 cone glaze?

[aaronlu]

May I ask, what would be the most effective way to increase the crackle to the glaze? I read online and it says to increase the silica and clay ratio to 1:1.25. What method would you recommend?

[ChannelDenoual]

Hi, thanks for the video! Where does the Blue color come from in Recipe 4, please?

[matheusmachadoalfradique]

I noticed that in a lot of the examples the glazes that form a significant amount of crystals instead of a purer glass (resulting in a Matte/Satin/Dry look) Phil states that It may not be food-safe depending on the colorants used that may leach out. My question is if by limiting the resulting looks (to only clear/shiny/transparent), the firing temperature, and the amounts of oxides and carbonates used as colorants I can build a safer practice in terms of food-safe pieces without the use of professional chemical analysis. Is there a regulations manual or written guide to help identify which oxides/carbonates I can use and under what conditions to ensure the safety of the pieces? I'm quite a bit lost on this particular matter and could use a good reference. Thank you.