tag:blogger.com,1999:blog-15240675.post4245440819904917981..comments2023-10-22T08:34:33.383-07:00Comments on Egyptian Paste (aka Faience): Some resultsanitrahttp://www.blogger.com/profile/06273181184408113726noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-15240675.post-50264522962485066322011-08-20T12:25:09.617-07:002011-08-20T12:25:09.617-07:00Can you fire egyptian paste in the same kiln used ...Can you fire egyptian paste in the same kiln used for clay pieces that are finished with commercial glazes?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-15240675.post-67235188649043825062010-10-26T06:22:45.918-07:002010-10-26T06:22:45.918-07:00Hi Ajda, sorry for the slow reply but I have been ...Hi Ajda, sorry for the slow reply but I have been away for weeks. Hmm interesting - I guess it could be sodium chromate that is developing. I do not use straight chrome in my mixes (but I do uses some stains and there is possibly chrome in those). I am concerned of toxicity levels and endeavour to take care in my handling of powders and oxides. I wonder if it is more toxic during firing..... I did speak to someone in the industry who was surprised that I was experiencing this problem at such low temps and he suggested firing with the kiln bungs open for the entire firing. I have only just made a batch of beads to test fire on the weekend - so will leave the bungs out and see what happens.<br />In response to your qstn, I have never fired porcelain so do not know if you will experience these problems - but I do remember reading online somewhere about an artist making porcelain beads and having this problem with the white beads. So I guess there is a possibility. Good luck and let us know.krikethttps://www.blogger.com/profile/10350962289836481175noreply@blogger.comtag:blogger.com,1999:blog-15240675.post-5809816819285958942010-08-22T01:54:00.299-07:002010-08-22T01:54:00.299-07:00I'm not a chemist any more than I am a ceramic...I'm not a chemist any more than I am a ceramicist, but chromium and sodium do form a compound with oxygen - Na2CrO4 - known under several different names, most commonly Sodium Chromate. It is bright yellow in colour and is used as a pigment in certain dyes. Do you think you might be producing that? It is quite a nasty toxic (possibly carcinogenic) compound - though I imagine in tiny quantities encased in glaze it couldn't pose any significant risk... It might, in any case, be worth talking to a chemist to see if they could explain what's causing it and how you could prevent it.ajdahttps://www.blogger.com/profile/02210293841616806772noreply@blogger.comtag:blogger.com,1999:blog-15240675.post-74200162144688888842010-08-22T01:32:46.001-07:002010-08-22T01:32:46.001-07:00Kriket - this is all most interesting to me. I'...Kriket - this is all most interesting to me. I'm hoping to learn how to make accurate replicas of faience beads from Egyptian and Roman times. I'm not a ceramicist, but I am also keen to experiment some day with porcelain, which of course needs even higher temperatures... So, what would you use for firing porcelain beads? Would you expect to see the same problems with nichrome that you're experiencing now? Or maybe it is to do with the sodium salts in the paste and so would not be an issue with clays.ajdahttps://www.blogger.com/profile/02210293841616806772noreply@blogger.comtag:blogger.com,1999:blog-15240675.post-86995256570288736372010-08-17T22:32:16.520-07:002010-08-17T22:32:16.520-07:00We have Lots of very different issues to address h...We have Lots of very different issues to address here on the eve of my hiatus from the Internet for two weeks. But I'll try to head you off at the pass here. The stainless steel wire has high chrome content, 10% or more depending on the quality. <br />· Using stainless steel will probably multiply your problem by a factor or two. The iron component of stainless steel wire contains a host of undesirable properties too. But by all means try it just to prove it won't work. My opinion, is you can learn more from a solid failure than a marginal success. <br />· What are you using for your green colorant? Does it contain chrome?<br />· Enamel!!? <br />· Kiln wash for Egyptian paste is a one-to-one ratio of aluminum hydrate to kaolin, that is by weight rather than volume. One omits the silica component of shelf primer. We need to be certain that we are on the same page.<br />· As for waxing, from what you described waxing isn't going to help. There are two types of wax hot wax and wax resist. For the hot wax, you would just dip it. For wax resist/emulsion; you painted on; normally one layer will suffice. Yes, wax burns off in the initial stages of the firing. Because we determined that that the flashing is happening in the kiln and not in the drying process, waxing is totally unnecessary.<br />· If you look back in this blog you'll find a video on making a bead tray/island. It renders down to a porcelain mandrel in the bead hole. Brush a couple of layers of kiln wash on the bead tray; your recipes forms thick glaze, you don't want to be drilling porcelain out from your holes. Therefore, the “island” will work for your 2 mm bead holes. There is serious doubt it will work for .7 mm holes, unless you are really perfect at tapering porcelain.<br /><br /><br />These are a few thoughts I had for just now. When I'm back online, I would have had time to ponder over it. Perhaps I'll come up with a solution. Did you run the experiment to see that the wire is the culprit? I'd like to see image of that BTW. Let's confirm we've identified the problem correctly.anitrahttps://www.blogger.com/profile/06273181184408113726noreply@blogger.com