yan6 Posted April 25, 2023 Report Share Posted April 25, 2023 Hi there, I'm just new here and completely new to ceramics as well. I just got an old electric duncan kiln and have been running it as purchased for a few firings now. The kiln shelves were pretty beat up and the wash had been flaking. As I'm starting to approach making things worth keeping i just redid the kiln wash by scraping off the ild with a wire brush and used PSH kiln wash. I decided to run just the shelves in the kiln a few days after the re-wash and they have started to show some dark spots. Are these of concern, did I do something wrong and what causes this. They kind look like mold spots, a greenish black. Quote Link to comment Share on other sites More sharing options...
yan6 Posted April 25, 2023 Author Report Share Posted April 25, 2023 Maybe I panicked too early, I just hit 1100degrees and they seem to have mostly disappeared ? Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
Mark C. Posted April 25, 2023 Report Share Posted April 25, 2023 What is PSH kiln wash-somethiong premade? Quote Link to comment Share on other sites More sharing options...
Min Posted April 25, 2023 Report Share Posted April 25, 2023 Hi and welcome to the forum! Watch the kiln wash going right to the edges of the shelves, about 1cm without wash would be safer around the edges so you don't have it flake off onto the shelves below. (@Mark C., PSH is Pottery Supply House in Ontario aka same company as Euclids elements) Pres 1 Quote Link to comment Share on other sites More sharing options...
yan6 Posted April 25, 2023 Author Report Share Posted April 25, 2023 (edited) Min, thanks for that comment, it makes perfect sense and I'll scrape off the edges once it's cooled down Hi Mark, sorry about that I should have been more clear, it's hi-aluma kiln wash https://psh.ca/products/5kg-glass-kiln-wash?_pos=2&_psq=kiln wash&_ss=e&_v=1.0 Edited April 25, 2023 by yan6 Quote Link to comment Share on other sites More sharing options...
neilestrick Posted April 26, 2023 Report Share Posted April 26, 2023 The black spots are just organic stuff. You'll see that on pots, too, as they heat up. Once you get above 1000F degrees they burn out. Pres 1 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted April 26, 2023 Report Share Posted April 26, 2023 14 hours ago, yan6 said: i just redid the kiln wash by scraping off the ild with a wire brush and used PSH kiln wash. I decided to run just the shelves in the kiln a few days after the re-wash and they have started to show some dark spots Just asking, these have been fired several times and if yes to what temperature? Also curious about scraping off the lid. Did you kiln wash the underside of your lid? Quote Link to comment Share on other sites More sharing options...
Min Posted April 26, 2023 Report Share Posted April 26, 2023 10 minutes ago, Bill Kielb said: Just asking, these have been fired several times and if yes to what temperature? Also curious about scraping off the lid. Did you kiln wash the underside of your lid? I'm guessing "... ild ..." is old not lid? Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted April 26, 2023 Report Share Posted April 26, 2023 Makes sense, but if fired several times, then how high was my curiosity there. Quote Link to comment Share on other sites More sharing options...
yan6 Posted April 26, 2023 Author Report Share Posted April 26, 2023 (edited) I didn't kiln wash the lid and it doesn't look as though it has been previously, should it be? To me I wouldn't make sense since it's soft fire brick. *edit: you must mean a topmost shelf that acts as a lid I'm short on shelves and don't really have one dedicated to this yet. Also all the shelves I inherited are half shelves The shelves had been fired previously to cone 6 a few times on my watch and presumably before I bought the kiln I scraped them off as much as I could by hand before applying my new wash. After the wash I only fired the shelves to 1100degrees Celsius Edited April 26, 2023 by yan6 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted April 26, 2023 Report Share Posted April 26, 2023 Thanks, no don’t kiln wash your lid, I just asked because with the typo in your post it appeared you might have. I asked about the temperature of firing the shelves because if fired hot enough, those dots are likely not carbon. So since you fired to 1100c, those dots are probably not carbon or organics and may not go away with further firing. Quote Link to comment Share on other sites More sharing options...
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