clay lover Posted September 27, 2011 Report Share Posted September 27, 2011 I use glazes that have been run through Hyperglaze, and there is a lot of info on the recepie sheet that I have yet to know enough to profit from. One piece of info I understand is the the silica/alumina ratio as a guide to how shiney or matt a glazz will be when fired correctly. I have a glaze that is rated 4.6:1 making me think it would be definitely matte. But when fired it is very glossy, even when cooled very slowly. Other glazes in the same kiln at the same firing rate will come out satin or matt, but not this one. Can someone educate me more on this subject? Thanks Link to comment Share on other sites More sharing options...
neilestrick Posted October 5, 2011 Report Share Posted October 5, 2011 Can you post the recipe? Any chance there is soda ash in the glaze? Link to comment Share on other sites More sharing options...
clay lover Posted October 23, 2011 Author Report Share Posted October 23, 2011 Sorry I missed your question, I've been away for a week. Thanks for responding. Recipe is; Nepheline sy 47 dolomite 10 ball clay 10 gerstly borate 23 tin oxide 5 zircopax 5 add 3% bentonite This glaze is great on darker clays with carvings, but why is it shiney with a S/I ratio of 4.6 to 1? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted October 23, 2011 Report Share Posted October 23, 2011 What cone end point are you firing to? best, ...............john Link to comment Share on other sites More sharing options...
clay lover Posted October 23, 2011 Author Report Share Posted October 23, 2011 ^6 , 2195* with a 20 minute soak does perfect tip touching cones all throught my kiln now that the mother board works correctly. Ya! I do the stepped down cooling that Hessleberth recommends and other glazes are soft satin matt, but not this one. Link to comment Share on other sites More sharing options...
Benhim Posted October 24, 2011 Report Share Posted October 24, 2011 Gerstley Borate is low melting at 1600 F, or cone 010. I can't imagine that at 23% it would be easy to make a glaze go matte. Maybe if the rest of the glaze was clay it would be matte?? What you've listed there looks like an opaque glossy glaze to me that would probably start to melt out at about cone 1 - 3. Link to comment Share on other sites More sharing options...
clay lover Posted October 24, 2011 Author Report Share Posted October 24, 2011 I don't know where it came from, but lots of people at the school where I am have used it for years, great on carving, brown if thin, white on porcelaine, always shiney unless very thin, not runny and fired to ^6. When it is put through Hyper Glaze it is listed as having a silica/alumina ratio of 4.6 to 1. Link to comment Share on other sites More sharing options...
Benhim Posted October 25, 2011 Report Share Posted October 25, 2011 4.6 silica to 1 alumina makes sense. That glaze has very little clay, and consists of mostly feldspar, borate and flux. Link to comment Share on other sites More sharing options...
clay lover Posted October 25, 2011 Author Report Share Posted October 25, 2011 4.6 silica to 1 alumina makes sense. That glaze has very little clay, and consists of mostly feldspar, borate and flux. And my question is, with that ratio, why isn't it a matt glaze ? I was taught that the ratio is a good indicator as to howw matt or shiney a glaze is. Link to comment Share on other sites More sharing options...
Benhim Posted October 26, 2011 Report Share Posted October 26, 2011 Here are some articles that can help explain some of your questions. Rather than listen to me it might help more to hear it from the horses mouth. This article explains gerstley borate in pretty good detail. This might help you understand the role gerstley borate is playing in your glaze. http://digitalfire.com/gerstleyborate/material/m-0101v0.htm To understand the matte article you should read this article about the glossy base glaze. http://digitalfire.us/4sight/education/g1214w_cone_6_transparent_base_glaze_121.html Then this article might help you understand the matte cone 6 glaze. http://digitalfire.com/4sight/education/g1214z_cone_6_matte_base_glaze_122.html Link to comment Share on other sites More sharing options...
Guest JBaymore Posted October 26, 2011 Report Share Posted October 26, 2011 Excellent reference to supply to them there, benhim. Anyone who is not familiar with DigitalFire.com and the Insight glaze chemistry software should do themselves a favor and check it out. A Level II program purchase is a GREAT deal that opens up some awesome online reference materials that are not available for free or in the Level I version of Insight. That Level II is the minimum purchase that I use with my undergraduate students in the ceramic materials course at my college. http://digitalfire.com/index.html best, ..............john Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.