sulamaye Posted October 4, 2015 Report Share Posted October 4, 2015 Has anyone got any ideas what is happening here? I am using Rhodes white stoneware glaze, same recipe, same materials from same buckets as I have used for years and yet on my last batch and worse still on this latest load some of the glaze is peeling as illustrated in photo. When it happened in last batch I remixed a whole new pot of glaze just to be on the safe side. Has anyone seen this? Is it the clay, the glaze or something else? I took the side bung out to put a thermocouple in when it was 650 c but closed it again, otherwise did not crack it until below 200 as usual. Any advice gratefully received as these are my Xmas orders and I've had enough trouble having had to borrow a kiln while my old one goes to the menders. Ahhh it's been a bad year, I was hoping my luck was changing. Thank you for reading Link to comment Share on other sites More sharing options...
oldlady Posted October 4, 2015 Report Share Posted October 4, 2015 so many pretty birds! so sorry this is happening. i think the correct term for this is "crawling". i cannot help but there are lots of previous threads about crawling and some of the glaze experts may be able to suggest something. Link to comment Share on other sites More sharing options...
bciskepottery Posted October 4, 2015 Report Share Posted October 4, 2015 You mention using a different kiln . . . is the firing schedule for the kiln the same as your old one? Or is it firing faster or slower? For your previous firing, did you use the borrowed kiln or your own? Is any of the glaze spitting onto the kiln shelves? Was the glaze dry when you loaded the kiln or still damp? Typically, crawling occurs when the glaze is applied too thick. You can also get a result like this if the firing is too fast. Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 Thanks for your reply . The first lot were fired in my old kiln, this lot in the new kiln. The glaze was dry when i painted the colours on and dry when it entered the kiln. It did not spit. Not all of them have done it. I must have dipped in excess of 18,000 birds so far in my life and if it's ever too thick it never goes like that, just a bit thick, in fact sometimes i like it when its a bit thick, more mossy looking, but I've never managed to get it so thick it did this and these were not thick, I'm pretty expert at judging that after so many years of churning out the critters Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 ps there was no sign of any problem when I put them in the kiln, nothing to indicate they were beginning to crawl. I have some left over to fire and they look just like they usually look before firing. Plus all the robins on the lower levels were fine so i don't think it was the firing. Perhaps there was a contaminate in the old glaze and the bluetits were dipped in that, it's just that it's so long siince I glazed what with having to get the kiln sorted that I have forgotten. I can't think what could have contamintaed it, it isn't like it was always doing it, I'd dipped plenty in it before it started going wonky. Thanks for your advice I will search 'crawling'. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted October 4, 2015 Report Share Posted October 4, 2015 Crawling can also be because of oily hands touching the pots before glazing. Link to comment Share on other sites More sharing options...
Min Posted October 4, 2015 Report Share Posted October 4, 2015 +1 for what Joel said, also could the bisque have gotten dusty before you glazed? Do you wipe them off with a damp sponge if they have been sitting around for a while before glazing? They are lovely! Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 thanks but I just don't think after ten years of glazing these I would suddenly start doing something different. Link to comment Share on other sites More sharing options...
Tim T Posted October 4, 2015 Report Share Posted October 4, 2015 Well obviously something has changed. Dust can be a culprit - could there be dust from when you changed the kilns over, and the birds picked some up? You don't say if you are using the same clay? Was the new glaze made out of materials you already had? - if not, ask your supplier if they have a different source or a different batch. Tim Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 Yes obviously something is different, but my methodology isn't, that's what I meant. I make, store, dip and decorate in the same way. Yes exact same materials that I have used for ten years, from the same bins,no new materials have been bought in that time. As I said it happened in the last kiln and the new one. Maybe some contaminant got into the batch of glaze, I have no idea what or why, but at least I now understand that something greasy could have caused this peculiar effect if it contaminated the bucket of glaze for some reason. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted October 4, 2015 Report Share Posted October 4, 2015 The reason I went for oils is because I feel a dodgy glaze would craze the whole batch. Maybe the clay? Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 Joel, I have wondered about the clay. I bought forty bags about two years ago so it was one of those bags, but have you ever known clay to have oils of some sort in it? It's certainly not something noticable when handling it, it is a right mystery and very frustrating. If I knew what it was I could be certain I'm not spending hours making only to have to chuck it in the bin. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted October 4, 2015 Report Share Posted October 4, 2015 Probably not oils in the clay, not sure what would make it happen. Only time I have seen crawling is too much clay in the glaze, too much zinc oxide and oily finger prints. Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 Not that then Joel. Only China clay, dolomite, whiting and feldspar, proportions tried and trusted. Not fingers, mine are clean and I hold the tiniest corner of tail to dip. Hmm do you think batt wash could have that effect if it contaminated? Clutching at straws here, but I guess a tiny bit could possibly have got into the bucket half way through? Link to comment Share on other sites More sharing options...
bciskepottery Posted October 4, 2015 Report Share Posted October 4, 2015 You mentioned the robins on the bottom turned out okay; but the bluetits on the top had the glaze issue. Could it have been something that contaminated the colorants used for decorating the bluetits? Link to comment Share on other sites More sharing options...
sulamaye Posted October 4, 2015 Author Report Share Posted October 4, 2015 That's what made me wonder if unremmebered by me the bluetit's had been dipped in the batch I threw a way , the robins were def recently done this week, but the bluet it's a little longer ago and my memory is bad, so perhaps that's all there is to it, but how that glaze got contaminated is beyond me unless a gremlin got some bat wash in it? Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.