PottaFella Posted March 12, 2015 Report Share Posted March 12, 2015 This is my clear glaze, it works either with or without the Lith Carb... it's a Michael Bailey recipe. Soda feldspar 70.0 Bentonite 3.0 Lith Carb 3.0 Dolomite 7.0 Zin oxide 5.0 Flint/Quartz 12.0 I am going to test it swapping the Soda feldspar for Nepheline Syenite, in an attempt to achieve that 'tide mark' I discussed in previous post. Can someone possibly tell me please... will it still be a balanced glaze? Or is the adjusted recipe likely to cause crazing problems etc? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted March 12, 2015 Report Share Posted March 12, 2015 Without doing calc..... you are increasing the soda content... the highest COE flux there is. Likely the overall COE will change so that it moves more toward crazing. And the lithium is the lowest COE material... so leaving that out also moves the glaze toward crazing. No time to do the calc now... sorry. best, .......................john Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 12, 2015 Report Share Posted March 12, 2015 The soda feldspar doesn't give you the nice burnt edges? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted March 12, 2015 Report Share Posted March 12, 2015 WHICH soda feldspar are you using? best, ...................john Link to comment Share on other sites More sharing options...
Tyler Miller Posted March 12, 2015 Report Share Posted March 12, 2015 It will likely craze, as it ups your COE significantly, but that's the cost of upping your soda content. Assuming you're using a soda spar like minspar, you're losing about 8% silica in the switch from soda spar to neph. sy. You can adjust the flint to compensate, but that would take you back in the direction of the glaze you had, just with different ingredients. I get the feeling that if you've got a balanced glaze, you might not get the effect you want. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 13, 2015 Report Share Posted March 13, 2015 WHICH soda feldspar are you using? best, ...................john I have never seen anything other than 'soda feldspar' being sold in the UK. Link to comment Share on other sites More sharing options...
PottaFella Posted March 13, 2015 Author Report Share Posted March 13, 2015 WHICH soda feldspar are you using? best, ...................john Sorry for delay, I checked packaging and it is just labelled 'Soda Feldspar' as supplied by CTM in exeter : ( Link to comment Share on other sites More sharing options...
Chilly Posted March 13, 2015 Report Share Posted March 13, 2015 I was looking at my sample tiles the other day, and almost every ^6 tile has that burnt toast around the edges of the glaze. By comparison, none of the ^06 have it. Most are commercial glazes. So is it more likely a combination of clay and firing temperature that causes the toast ???? Now I've read this thread, I'm going to go back and have another study of all the tiles. I think it doesn't notice so much on finished items as the glaze usually goes to the bottom, and for things with feet, the glaze goes around the bottom too. I'll report back. Link to comment Share on other sites More sharing options...
PeterH Posted March 13, 2015 Report Share Posted March 13, 2015 I checked packaging and it is just labelled 'Soda Feldspar' as supplied by CTM in exeter If it's any help to the discussion here is an analysis from CTM's site http://www.ctmpotterssupplies.co.uk/MSDSetc/H&S&specs/Spec%20Sheets/Soda%20Felspar%20Spec.pdf Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 13, 2015 Report Share Posted March 13, 2015 I use CTM and their soda feldspar gave me nice burnt edges. Will find the glaze recipe. Link to comment Share on other sites More sharing options...
Colby Charpentier Posted March 13, 2015 Report Share Posted March 13, 2015 Keep your recipe the same, spray a very light mist of soda ash at the edge of your glazes. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 14, 2015 Report Share Posted March 14, 2015 Cone 8-10 Soda Feldspar 30 Cornish Stone 30 Quartz 9 Dolomite White 10.5 Whiting 10.5 China Clay (Puraflo) 6.7 Tin Oxide 2.7 Cobalt Carbonate 0.6 TOTAL 100 The burnt edges seem less looking back but it is there. Link to comment Share on other sites More sharing options...
Chilly Posted March 14, 2015 Report Share Posted March 14, 2015 I had another good (proper) look at my test tiles..... The ones with the toasty look were all overfired ^6, probably to ^8, but as I only had 5/6/7 cones set, I can't be certain. But the same glazes fired to ^6 don't have the toasty look. The raw material sample that High Bridge re-posted in the other "toasty" thread also overfired. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 14, 2015 Report Share Posted March 14, 2015 So it looks like around cone 8 that the soda begins to volatilize. Link to comment Share on other sites More sharing options...
Babs Posted March 15, 2015 Report Share Posted March 15, 2015 HIgh Bridge your totalling to 100 is interesting. The tin oxide and cobalt being colourants , I would not be including in the percentage formula.... If it works use it?? But would be interesting to see what the glaze would be like if the percentages were worked for the first six components of this glaze. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted March 15, 2015 Report Share Posted March 15, 2015 Good spot Babs, I never even noticed. This was the very first glaze I started with so I am not surprised I included them in the total. Link to comment Share on other sites More sharing options...
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