An Introduction to Glaze Testing Part 2

[@jossycaro354]

Thanks Phil, so informative!

[@WashingtonStreetStudios]

Jossy, you are welcome. Share the channel with your friends and fellow potters to help us grow our community. And let us know if there is a topic you would like discussed!

[@sergeyponomarev8878]

Another great video! I love how you show glaze results and explain them! and also thanks for providing useful tips! Would love to see more glaze testing!

[@WashingtonStreetStudios]

Sergey, have you watched the Understanding Pottery series? If not, there are three videos on Tips for Successful Glazing, here is a link to part 1 (kzbin.info/www/bejne/faCchnRua6iAfbc). There is a video on Glaze Defects (kzbin.info/www/bejne/sICQiWBmd9ODiMU) and a video on Ash Glazes (kzbin.info/www/bejne/gn7Nf5h9hMSqmdU). And finally we just finished a video on Making Test Blends for Glazes and Clay Bodies (kzbin.info/www/bejne/sJLRpYl7n8t_o7s). If you've seen these, and still can't get enough, we understand, let us know what type of testing you would like to see! Keep watching and share the channel with your friends and fellow potters.

[@talicohen-flantz4099]

Love your videos so clear and inspiring!!! Keep up the amazing work that you do 💗👌

[@WashingtonStreetStudios]

We will, and please tell us if there are topics you would like us to explore.

[@ЮлияМихеева-ю2е]

Which oxides are solution colourants (I see, copper, but what about the others)? And which are suspension ones? Great insights about numbering tiles! Also, do you have any suggestions about solving crawling when layering glazes? I find that store bought glazes layer easily but glazes that I mix myself often crawl when I put one over the other Thank you so much for sharing!

[@WashingtonStreetStudios]

Flia, I hope my transliteration is correct, I have forwarded your question to Phil and will post his response when I receive it. Thanks for the questions and support, please share the channel with your friends and fellow potters!

[@WashingtonStreetStudios]

The behavior of a colorant, whether it acts as a suspension or solution colorant, really depends upon the form of the colorant and not the particular chemical element. All of the common colorant elements such as copper, chromium, cobalt, manganese, and iron can behave as solution colorants when they are in the form of compounds such as oxides, carbonates, or sulfates. However, if these elements are combined with other ingredients to produce colored materials that are resistant to dissolving in a glaze, then the resulting combinations will behave as suspension colorants. This is what ceramic strains such as Mason stains are, colored chemical compounds that are designed not to dissolve. One complicating situation is that every compound that can dissolve in a glaze has a limit as to the amount that can actually dissolve (depending upon a number of factors such as the composition of the glaze and the firing temperature). Once this limit is exceeded, then any additional amount of the colorant that is present will then behave as a suspension colorant. This is the situation with high-iron glazes such as temmokus, for example. The maximum amount of iron possible has dissolved in the glaze, but the color of these glazes is dominated by the excess iron oxide (in suspension) that has not been able to dissolve in the glaze. When layering glazes, it is important not to let the first glaze dry completely before the second layer of glaze is added, although this may sound counter-intuitive. The second layer should be added when the first layer is still damp, but has dried to the point where it is no longer wet to the touch. The commercial glazes are not quite as sensitive to this because they usually contain an organic gum, such as cellulose gum, that slows down the drying of the glaze. Phil

[@freddiemoretti8456]

On cooling down after reaching target after soak, would you recommend turning of the Envirovent or experiment for any differences?

[@WashingtonStreetStudios]

Freddie, I've forwarded your question to Phil and will post his response when I receive it!

[@freddiemoretti8456]

@@WashingtonStreetStudios Thank you!

[@WashingtonStreetStudios]

Hi Freddie, Electric kilns cool down very quickly, so I don’t think that turning off the kiln fan would slow down the cooling enough to significantly change the glaze; you’d have to do a programmed cooling to accomplish that. But, if your fan is located under the kiln, then it would be a good idea to leave it on anyway to provide cooling for the fan (the fan draws in room air and mixes it with the hot exhaust from the kiln). Phil

[@freddiemoretti8456]

@@WashingtonStreetStudios Thanks Phil, my fan is safely on the wall, kiln is on the floor so all good.