Arimajol Posted August 23, 2022 Report Share Posted August 23, 2022 Hi! I just unloaded a kiln and I have that sinking feeling we all know. I had mixed glaze prior to this firing, the same glaze I've been using for about 5 years. There are small white bits in the glaze, I'm fairly certain that it is an undissolved ingredient. It is uniformly distributed across most of the pots in the kiln. I seived the glaze 3 times in mixing. The seive is mesh 60, but was sold as a glaze seive. Now I'm seeing that glaze should be mixed with a 80-100 mesh seive. That's frustrating. I haven't had this problem before. Two questions: 1. How can I keep this from happening again and salvage the bucket of glaze I just made with crazy expensive tin oxide? Should I get a different seive? 2. Anything I can do to salvage this kiln load? Is it a bad idea to just sand down the bits? I can't provide them to customers like this. Thank you! Quote Link to comment Share on other sites More sharing options...
Pres Posted August 23, 2022 Report Share Posted August 23, 2022 Some pictures would be helpful, hard to tell what is going on with just a description. best, Pres Quote Link to comment Share on other sites More sharing options...
Arimajol Posted August 23, 2022 Author Report Share Posted August 23, 2022 Here is a photo Quote Link to comment Share on other sites More sharing options...
Pres Posted August 23, 2022 Report Share Posted August 23, 2022 It looks to me that they are larger than sieve size, but not certain of that. First thing I would do is to re-sieve the glaze to see if you get any particles in the sieve. Secondly, even though the glaze looks to have gone on evenly, did you wash the pot before hand? Did the pot set out before glaze firing? Was this on a lower shelf that had a shelf above with kiln wash on the bottom side? Had to ask. Is this in a bowl? best, Pres Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted August 23, 2022 Report Share Posted August 23, 2022 I’m leaning towards loading error, not glaze ingredient. That looks like shelf wash crumbs. They’re dry and refractory, and sitting on top of the glaze, not coming up from within it. If it is shelf wash, yes, you can try grinding them down a bit, dabbing a little bit of glaze back on and re-fire. And be extra careful to give the shelves a light brush with your hand before you place them. Quote Link to comment Share on other sites More sharing options...
Arimajol Posted August 23, 2022 Author Report Share Posted August 23, 2022 34 minutes ago, Callie Beller Diesel said: I’m leaning towards loading error, not glaze ingredient. That looks like shelf wash crumbs. They’re dry and refractory, and sitting on top of the glaze, not coming up from within it. If it is shelf wash, yes, you can try grinding them down a bit, dabbing a little bit of glaze back on and re-fire. And be extra careful to give the shelves a light brush with your hand before you place them. That kinda makes sense. Some of the chunks are big enough that there's no way they passed the seive. Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted August 23, 2022 Report Share Posted August 23, 2022 I’ve done it, and I know the pain of that realization! At least the fix is straighforward. Quote Link to comment Share on other sites More sharing options...
Arimajol Posted August 23, 2022 Author Report Share Posted August 23, 2022 1 hour ago, Pres said: It looks to me that they are larger than sieve size, but not certain of that. First thing I would do is to re-sieve the glaze to see if you get any particles in the sieve. Secondly, even though the glaze looks to have gone on evenly, did you wash the pot before hand? Did the pot set out before glaze firing? Was this on a lower shelf that had a shelf above with kiln wash on the bottom side? Had to ask. Is this in a bowl? best, Pres The bisque was sponged and rinsed before glazing to clean out dusty matter, and was glazed an hour or two after cleaning. This particular piece is a cup. The chunks are on the inside vertical wall, not just on the bottom. Does that point to it not being kilnwash? The shelves do not have kiln wash on the bottom. Chunks were even in the ware in the top shelf, which did not have a shelf above. That points to it being in the glaze, I'd think. I do remember when seiving that there were some larger gritty particles. Quote Link to comment Share on other sites More sharing options...
neilestrick Posted August 23, 2022 Report Share Posted August 23, 2022 They look like kiln wash chunks to me, too. I think you would have noticed them when you applied the glaze if they were in the glaze. Run the glaze through an 80 mesh sieve and see if you get anything on the screen. Pres 1 Quote Link to comment Share on other sites More sharing options...
Pres Posted August 23, 2022 Report Share Posted August 23, 2022 Sounds like you need to re sieve. If you can get an #80, I would try that. I always sieve twice, once into a spare container, then back into the original container after cleaning it and the sieve. best, Pres Quote Link to comment Share on other sites More sharing options...
Min Posted August 23, 2022 Report Share Posted August 23, 2022 11 hours ago, Arimajol said: I seived the glaze 3 times in mixing. Did you sieve the glaze when you made it up 3 times or just before you used it? Glazes containing soluble materials (including boron frits) can form bits (scale) on the sides of the buckets and in the slurry over time. Other materials, like wollastonite can agglomerate causing "bits" in the glaze slurry. If you use hard water this will exacerbate the solubility problem. Image below from digitalfire that looks an awful lot like your problem, cause was soluble materials causing scale bits. #1 for using an 80 mesh screen. I would take a Dremel tool and grind them out then apply a small amount of (screened) glaze to those bare areas and refire to a slightly cooler cone. If you went to ^6 before try just over ^5. dhPotter 1 Quote Link to comment Share on other sites More sharing options...
Arimajol Posted August 23, 2022 Author Report Share Posted August 23, 2022 4 minutes ago, Min said: Did you sieve the glaze when you made it up 3 times or just before you used it? Glazes containing soluble materials (including boron frits) can form bits (scale) on the sides of the buckets and in the slurry over time. Other materials, like wollastonite can agglomerate causing "bits" in the glaze slurry. If you use hard water this will exacerbate the solubility problem. Image below from digitalfire that looks an awful lot like your problem, cause was soluble materials causing scale bits. #1 for using an 80 mesh screen. I would take a Dremel tool and grind them out then apply a small amount of (screened) glaze to those bare areas and refire to a slightly cooler cone. If you went to ^6 before try just over ^5. I seived back and forth between two buckets three times, mixed with remnants from the last batch. I didn't spend much time mixing before seiving and maybe that's where I went wrong. I tried to use some 120 frit sandpaper and hand sand one down and it barely scratched it. Dremel is definitely the way to go. Thanks for that tip! Quote Link to comment Share on other sites More sharing options...
Arimajol Posted August 29, 2022 Author Report Share Posted August 29, 2022 Hi all, just wanted to follow up for posterity and with gratitude. I followed the advice to Dremel the chunks and and dab to fill and it worked pretty nicely. Difficult to reapply a consistent amount of glaze, but it's good enough. As to the root of the problem, I re-sieved and did something I've never done before: cleaned out the glaze bucket. I always sieve back and forth, ending up in the old bucket that has 5 years of crust all along the sides. This time I cleaned all the crusted glaze off. I suppose I could have scraped and mixed it in well, breaking up chunks and I may do that in the future. Cheers! Babs, kristinanoel, Hulk and 1 other 4 Quote Link to comment Share on other sites More sharing options...
oldlady Posted August 29, 2022 Report Share Posted August 29, 2022 BUY A RUBBER SPATULA AND ALWAYS CLEAN EVERY BUCKET! the 60 mesh sieve has worked for me since 1972. wore out one or two. Chilly 1 Quote Link to comment Share on other sites More sharing options...
kristinanoel Posted September 7, 2022 Report Share Posted September 7, 2022 So glad you solved this problem! I had it a while back, mine was also a sieving problem. In looking for the cause, I also came across this great post that talked about the importance of blending. Enjoy! https://glazy.org/posts/173081 Callie Beller Diesel and Roberta12 2 Quote Link to comment Share on other sites More sharing options...
Babs Posted September 7, 2022 Report Share Posted September 7, 2022 2 hours ago, kristinanoel said: So glad you solved this problem! I had it a while back, mine was also a sieving problem. In looking for the cause, I also came across this great post that talked about the importance of blending. Enjoy! https://glazy.org/posts/173081 Bit like discussion of finer grades of Silicone carbide in the current lava glaze post. Quote Link to comment Share on other sites More sharing options...
Mark C. Posted September 7, 2022 Report Share Posted September 7, 2022 80 mesh screen always fixes any chunk issue Pres 1 Quote Link to comment Share on other sites More sharing options...
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