carolross
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I've had the same problem and still do sometimes. The bubbles on my work looked just like yours. Although there were suggestions about needing a longer bisque for outgassing, I did 12 hr bisques (elec) and that didn't help. Certain underglaze colors produced the bubbles more consistently than others. I spoke with a chemist at Amaco who couldn't resolve it for me. What finally made a difference for me was changing the commercial underglazes and glaze I use, from Amaco to Mayco. Perhaps an incompatibility with the clay I use? I don't know if that info will help...
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What happened? Refiring earthenware pottery to repair
carolross replied to skessel1's topic in Clay and Glaze Chemistry
I’ve had lots of similar problems... and spent a long time trying to find out why they occurred. Sometimes it seemed like one particular color underglaze might be problematic. So, I learned that underglaze ages... How long has it been since you opened the jar of blue underglaze? Underglaze does get old and separates, causing adhesion problems. If that’s the case with your blue & you’ve had a while, adding some gum Arabic to the underglaze should help. Because it only happened with the blue and not the other colors, this might be why... Good luck! -
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Wooooo-hooooo! Fabulous (if small) glaze firing! Yay cone 06! Yay for everyone's help!
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- clearglkaze
- dipping glaze
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Hey Min & Pleasant Pottery! So far, things are looking hopeful. I did a bisque fire last night to ^06 and the glaze went on sooo smooth! Not a single webby area, even though two of the pieces were in the same turquoise that has always produced the webbed pattern. Yay! And thank you! I'm firing to 5 with a 10minute hold that pushes it to 6, so we'll see tomorrow... iIt was reassuring to hear about your experience, Pleasant Pottery - clever of you, too. And Min, about the orange underglaze. I had the same thought, that I should try a different brand. Amoco's Flame Orange is encapsulated (read costly) and I love it. Mayco doesn't have anything like it, so I ordered ... yup... Spectrum's Neon Orange. LOL. Maybe it will be okay on my clay body, which is Laguna 609 - what do you use? Or maybe I'll look some more... Did I say thank you? This has been a nuisance for ages and I'm optimistic this will resolve it. So a Huge Thank You!
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I do rinse the bisque ware under running water before I dip it. I run my bisqued pots under water and wet sand them, and then I dry them out for a couple of days before glazing. Otherwise the glaze does WEEEEIRD stuff and takes forever to dry, especially over underglazes that have been fired once. If you do this and then put directly into the kiln it can even "fall off" because it is just not adhering well to the surface of the pot. Hey Giselle and Min, Thanks for your suggestions! Giselle, when I rinse the bisque ware, I do it quickly and it seems to dry fast - at least on the surface. I'll try waiting next time and see if that helps ) And Min - when I read about reducing the bisque to ^06, ding ding ding! Everything just felt right -I think you've nailed it. Because this weird webbing happens with specific colors, I'm thinking you're right, they may be fluxing. It does't happ with, say orange - but orange tends to peel away from edges and leave little spaces uncovered... So maybe... Fingers crossed! Thank you all - I appreciate your help!
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Hey Denise & Diesel Clay - I apply the underglaze to leather hard clay & then sgraffito. Bisque at ^04, then apply glaze and fire ^5. If I remember, sigh, I do rinse the bisque ware under running water before I dip it. I've switched to Mayco underglazes from Amaco whenever the colors are similar enough and that does seem to have helped. Guess I'll look at other brands for the few Amaco I haven't been able to duplicate... Thanks, guys, it sounds like a plan )
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I know - it's actually beautiful! And it does blend out during the ^6 firing. But I think there's gotta be a problem hiding here somewhere.... I'm in St. L, too, btw...
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Hi Denice, Okay, to be sure we're on the same page - the mugs have been bisque'd to 04 and this is the first time I'm glazing them. And YES! I've had problems with glaze not adhering to some areas of the underglaze. I posted about it last year, actually, and resolved it, mostly, by making sure the glaze is not too thin, especially on edges. It's weird, though, because both the underglazes and glaze are Amaco products - wouldn't you think they'd work well together? Do you have any suggestions about what to do? This pattern occurs mostly on black and turquoise (Velvet & LUG)...
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Thanks for your reply. Actually I use some Mayco underglazes, but notice this happening on Amaco's products. And it happens most often on black and turquoise (Velvets and LUG). And... these mugs were slowly bisque'd to ^04. But I think you're on the right track...
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Yes, they are hand built, but the slabs are moved from canvas to dry-wall and rib-smoothed in all directions. So, I don't think that's it - thanks though!
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I've had this happen occasionally, but now it seems to be more frequent. After dipping a mug in a commercial clear glaze, the surface has an odd pattern, like webbing. I think this happens only on mugs, but that seems pretty weird. Usually on the inside, but the outside and handles are also affected sometimes. I don't know if it's coincidental (there are no...?), but it happens with certain underglaze colors primarily. Does anyone know WHY this happens? Is there anything anyone can suggest? I think it fires pretty well, the pattern melts, but I'm always concerned it won't... Thanks for your help! Carol
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Clear Glaze Forms Bubbles At Edges & Rims
carolross replied to carolross's topic in Clay and Glaze Chemistry
Hi Neil - thanks for posting. My original problem (starting 3-4 years ago!) was with Amaco Med Blue Underglaze glazed with Amaco low zinc HF-9 glaze. That produced these bubbles... Wouldn't products from the same manufacturer be compatible? I switched to Mayco UG-97 Bight Blue and kept the same HF-9 glaze. Bubbles. Tried Mayco clear glaze - bubbles. I only recently tried the blue slip - obviously I have little experience making slips, but did some readin and said oh, what the hell? And mixed it w/ 30% blue mason. I'd tested other colors using under 10% and for the most part, they were washed out. An engineer at Amaco looked at a greenware piece I'd put UG on a couple of years ago. He was surprised, but the inderglaze wasn't too thick. From the tests I just posted and pieces I've fired recently, I think maybe I've used too little glaze... -
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Clear Glaze Forms Bubbles At Edges & Rims
carolross replied to carolross's topic in Clay and Glaze Chemistry
Here are the other 2 photos - one each of the whole disk. Thanks! -
Clear Glaze Forms Bubbles At Edges & Rims
carolross replied to carolross's topic in Clay and Glaze Chemistry
Hi Curt! I did the tests - 2 disks, one of each clay - and I dried them in a convection oven (moving air) at 200 degrees. I hope you're able to see everything clearly - if not, I can retake the photos, just let me know. I'm really looking forward to your response - thanks you! There are 6 jpgs - don't think I can get them all in one post, so please check the next one, too. -
Clear Glaze Forms Bubbles At Edges & Rims
carolross replied to carolross's topic in Clay and Glaze Chemistry
Curt - okay I'll come out from under the slab roller where I've been hiding and I'll do it! And will post the results! Thanks for the suggestion. Joel - that's an interesting thought... I'll definitely give your suggestion a try. 'Cause if I fire this new clay and get the same bubbles and stuff... thank you!
