Lbegley Posted March 14, 2019 Report Share Posted March 14, 2019 I have a vanadium underglaze recipe that changes color from yellow to green (only wet in the container, it fires yellow). The color shift makes mixing colors difficult, and I’m hoping someone here has a solution to curb the growth of whatever microbes are changing its color. Link to comment Share on other sites More sharing options...
oldlady Posted March 14, 2019 Report Share Posted March 14, 2019 bleach works. just a little unless the staining has spread throughout the liquid. happens with my slips which i use for several years and i just bleach it out. Link to comment Share on other sites More sharing options...
Lbegley Posted March 14, 2019 Author Report Share Posted March 14, 2019 Is firing the bleach hard on the kiln elements? Chlorine gas is pretty corrosive, no? Is the amount used not enough to cause problems? Link to comment Share on other sites More sharing options...
liambesaw Posted March 14, 2019 Report Share Posted March 14, 2019 Is this an underglaze you make or one you buy? I'd think a store bought one would have a preservative. Keep it out of the light would prevent algae as well. Link to comment Share on other sites More sharing options...
Lbegley Posted March 14, 2019 Author Report Share Posted March 14, 2019 I make it and it lives in a windowless room, in an opaque container, so I guess you’re right and it’s probably some other microorganism, not algae. Whatever it is, it only lives in the vanadium underglaze, none of the other mason stains seem to change color, but the base does bubble when it’s freshly made like it’s fermenting! I’m going to try some vinegar and see if a ph change is enough to make it less appealing to the buggers. Link to comment Share on other sites More sharing options...
Min Posted March 14, 2019 Report Share Posted March 14, 2019 @Lbegley, a tiny bit of copper carbonate added to brushing medium stops the gums in the brushing medium from rotting, magma glaze additive suggests using copper also. The amount used is so small that it doesn't effect the colour. Same principle would apply to underglazes as glazes. By weight it would be 0.04% copper carbonate, like everything ceramics, if you try this test a small amount first. Link to comment Share on other sites More sharing options...
Lbegley Posted March 14, 2019 Author Report Share Posted March 14, 2019 5 hours ago, Min said: @Lbegley, a tiny bit of copper carbonate added to brushing medium stops the gums in the brushing medium from rotting, magma glaze additive suggests using copper also. The amount used is so small that it doesn't effect the colour. Same principle would apply to underglazes as glazes. By weight it would be 0.04% copper carbonate, like everything ceramics, if you try this test a small amount first. Thank you! I will test copper carb. Link to comment Share on other sites More sharing options...
Lbegley Posted April 26, 2019 Author Report Share Posted April 26, 2019 Update! I added 0.05% copper carb to my engobe base, and it seems to have worked! It doesn't effect the color fired and after a month it hasn't changed in the bottle (my control batch is green and stinky, so success!). The only bummer is that it is such a small percentage, that in order to measure it, I need to make a pretty large batch. I also tried vinegar which also worked to keep the engobe changing color, but changed the consistency, and the solids collected at the bottom. Link to comment Share on other sites More sharing options...
dhPotter Posted April 26, 2019 Report Share Posted April 26, 2019 Measure 1 gram. Using a knife or other straight edge, divide the pile by half, then divide a pile by half, then divide the pile by half, then divide by half. This gets you to 0.0625 Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.