Dan_W Posted December 31, 2019 Report Share Posted December 31, 2019 Hi everybody. I've recently started working with ceramics in loose connection to some architectural research I'm undertaking. I'm trying to make a crater glaze, which according to everything I've read, shouldn't be so hard (right?!?!?). For my starting point, I've made a number of variations using this recipe as a guideline: https://glazy.org/recipes/21422 However, when being fired (kiln sitter, cone 6) nothing is happening. The glaze is coming out identical to when it goes in, as with this morning's heartbreak: The same results have happened regardless of the clay body or increases in the silicon carbide. Strangely, when I applied the mixture to a broken scrap which had already been glazed, there did seem to be a reaction with this pre-existing commercial glaze. I'm wondering if there might be some rookie issue I am overlooking here? Any help would be greatly appreciated and would leave me indebted to you for life Link to comment Share on other sites More sharing options...
neilestrick Posted December 31, 2019 Report Share Posted December 31, 2019 It's just not melting. Just looking at that recipe I'd say it's more geared towards cone 10, not cone 6. You can get a crater effect by adding silicon carbide to just about any glaze that melts well. If I were you I'd start with a recipe that you know works. Link to comment Share on other sites More sharing options...
Min Posted December 31, 2019 Report Share Posted December 31, 2019 The Glazy recipe you linked is basically the ^6 Marilee Lava glaze recipe. Amounts rounded off to whole numbers except the silicon carbide amount is a fair bit different. Glazy recipe is 1.2% versus 3.4% for the Marilee Lava recipe. Other variable might be the mesh size of the silicon carbide you use. I believe you will get a better crater/lava effect with a coarse grade of silicon carbide, about 100 mesh. I'ld do a progression blend, base plus 1% silicon carbide, dip or brush on a test tile then add another 0.50% silicon carbide and repeat. Keep going until you get up to 4%. Results are not going to be precise as each time you dip a tile you are removing some of the base amount but it will get you in the ballpark. I'ld probably do this test with a 200 gram base amount. (protect your kiln shelves with a good layer of wash and put the pieces away from the elements) Link to comment Share on other sites More sharing options...
Jays Posted January 1, 2020 Report Share Posted January 1, 2020 I’m just about to start experimenting with crater glazes and the plan is start on some test pieces with the Marilee recipe. Min, you mention protecting the kiln shelves and keeping away from the elements....I assume from that that I can expect some glaze splatter? If that is the case I assume I’m going to have problems firing pots on the same kiln shelf. Link to comment Share on other sites More sharing options...
Min Posted January 1, 2020 Report Share Posted January 1, 2020 Yes, they can spit. How far and how badly is going to depend on the glaze, might be an issue, might not be. One other thing, I've come across lava/crater recipes using cryolite or fluorspar, if you try those be very careful in the firing of them. Both cryolite and fluorspar release fluorine gas which is both a severe irritant and poisonous. If you find the glaze doesn't melt enough then bump up the whiting. Link to comment Share on other sites More sharing options...
liambesaw Posted January 1, 2020 Report Share Posted January 1, 2020 4 minutes ago, Min said: Yes, they can spit. How far and how badly is going to depend on the glaze, might be an issue, might not be. One other thing, I've come across lava/crater recipes using cryolite or fluorspar, if you try those be very careful in the firing of them. Both cryolite and fluorspar release fluorine gas which is both a severe irritant and poisonous. If you find the glaze doesn't melt enough then bump up the whiting. Nothing like a little hydrofluoric acid to brighten up your day Link to comment Share on other sites More sharing options...
Bill Kielb Posted January 1, 2020 Report Share Posted January 1, 2020 2 hours ago, liambesaw said: Nothing like a little hydrofluoric acid to brighten up your day Really dangerous delayed reaction or deep burns possible. Careful! Etches glass, go figure in a kiln full of glazed stuff. Link to comment Share on other sites More sharing options...
C.Banks Posted January 1, 2020 Report Share Posted January 1, 2020 Please be careful with fluorspar/cryolite/lepidolite. For some the drawbacks associated with it's use are not worth it. Link to comment Share on other sites More sharing options...
Dan_W Posted January 3, 2020 Author Report Share Posted January 3, 2020 Hi everybody. Just come back to this, really helpful! Going to jump back on it tomorrow and hopefully get some more tests fired. @Jays Really interested to see how you get along too...... Link to comment Share on other sites More sharing options...
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