Mid-Range Crater Glaze Tests

CO-72-1

CO-73-1

CO-73-2:5

• As the quantity of Titanium Dioxide in the glaze increases, bubbles begin to fail to pop, and instead result in a very droopy, marshmallow-like glaze. This is consistent with Titanium Dioxide being refractory, so the greater amounts cause the glaze to not quite reach maturity. This Titanium Dioxide appears to be contaminated with a small amount of red iron oxide. My preferred results in this firing come from only 2% Titanium Dioxide.

CO-74-1

CO-74-3:6

• As the amount of Titanium Dioxide increases in the glaze’s content, the amount of cratering that we see decreases as well. The appearance of the RIO Crater glaze in an electric kiln, compared to a gas reduction kiln, is vastly different - likely due to the gas kiln’s inability to fire in true oxidation. This glaze is already quite low-melt given Red Iron Oxide’s refractory effect in oxidation, so the cratering isn’t very significant. My preferred results come from only 4-6% Titanium Dioxide, however this glaze needs to be tested without any TiO2 as well.

CO-74-7:9

• The increase in nepheline syenite predictably leads to an increased melt of the glaze. Importantly though, this increased melt leads to more/larger cratering. My preferred result here comes from 72% nepheline syenite, as the others don’t crater very much. Before going forth with this though, this recipe needs to be tested with no titanium dioxide, and nepheline syenite may be adjusted from there.

CO-74-13:15

• It’s hard to specify what a lack of silica is doing to this glaze. As the amount of silica increases, the glaze takes on a thicker, and more solid texture, and interestingly, the red iron oxide in the glaze becomes more varied, with more distinct light and dark patches. The 4% silica test appears to be “washier” or a much thinner application, despite being applied, to my knowledge, identical to the every other tile. I struggle to translate knowledge of the conventional effects of silica to its effect on crater glazes. My preference here is with 8% silica. It would be interesting to due a more drastic step test of silica in just the base glaze, starting with 0%, and jumping to 30-50%. If I undertake this testing, I will update here.

CO-75-1

CO-75-2:5

• These results differ greatly from my expectations, as typically this copper crater provides significant effect, however the craters are often rather low on the surface, but also quite sharp;this may be chalked up the issue in the firing disclaimer above. Nonetheless, there are results to be gathered here. The bleaching effect of titanium dioxide is on full display here. As the amount of titanium dioxide increases, the saturation of the copper decreases, until the surface is instead varied spots of darker blues, and a cool white. Though the coloring of the 4% tile [far left] is closer to what I was after, the results seen with titanium dioxide at 8% [middle right] is quite interesting, and may be worth further exploration. This glaze should also be tested with no titanium dioxide whatsoever.

CO-75-6:9

• The same unexpected results mentioned above may be said for this glaze as well. Both of these should really receive retesting. Still the results here are logical and provide information on the effect of rutile with other oxides in crater glazes. The surface is again smooth, however instead of bleaching with increased rutile content, we see a gradual turn towards orangeness, due to the red iron oxide in the rutile. Interestingly, the cratering seems to increase with rutile, though this may be a fluke due to uneven heat throughout the kiln, as the rutile should have a refractory effect similar to titanium dioxide. The results seen with rutile at 4% and 6% are quite nice [left most tiles] due to the complementing orange and blue, especially the darker speckling varying the surface at 6%, and this may be a good candidate to eliminate silicon carbide from to create a satin matte glaze.

CO-76-1

CO-76-2:5

• This surface is far smoother than expected, likely due to the reasons in the firing disclaimer above. The bleaching effect of the titanium dioxide can be seen here, however it’s also creating some interesting variegation in the surface (particularly apparent at 8% content) [middle right] and an almost icy look once at 10% [far right]. These should be retested, with a proper firing the next time around.

CO-76-6:9

• These results almost mimic the results with cobalt carbonate at 1%, which likely points to an error in my testing. The only noticeable difference is what appears to be more iron in the titanium dioxide, most apparent with the 6% content tile [middle left], though this is likely simply due to the source of titanium dioxide being somewhat inconsistent. The expected result here would have the glaze be noticeably more blue and darker in value.

CO-77-1

CO-77-2:12 REPRESENT AN EXPERIMENTAL ERROR

CO-77-2:5

CO-77-6:9

CO-77-10:12

CO-78-1

CO-78-2:5

• As the amount of Strontium Carbonate increases, the glaze becomes smoother, with less pinholes, however the coloring stays roughly the same. This lines up logically, as the strontium carbonate is exhibiting its fluxing properties. The overall effect of the rutile in the glaze is quite pleasant, with a blooming orange where the glaze is thick.

CO-79-1

CO-79-2:5

• As the amount of mason stain increases, predictably, the blackness of this glaze darkens. My preferred sweet spot here is around 6-8% [base glaze for 6%, middle right for 8%]. As the amount of stain increases, it also appears that the glaze bubbles more, likely due to the presumably high iron content in the glaze offing gasses.

CO-79-7:10

• The titanium dioxide doesn’t appear to do very much bleaching, and instead is just smoothing the surface. This is likely due to the same refractory nature seen before, so not much of note happening here.

CO-81-1

• A metallic glaze that didn’t crater very much. Not very interesting, maybe worth firing again though due to mistakes in this firing?

CO-82-1

• An incredibly interesting metallic crater glaze that looks a bit like a messy weld. I would like to further test this glaze in the gas kiln

CO-83-1

CO-83-2:5

• As the amount of mason stain increases, the glaze becomes slightly more saturated. The texture is rocky, and consistent throughout, without any big difference in texture. I’m surprised that the difference between the tiles isn’t more distinct.

CO-83-7:9

• This result was quite surprising to me. Though I’ve seen titanium dioxide bleaching out colors, it’s very distinct here. The 0% titanium dioxide tile is far more saturated than the tile at 4%. I’m surprised to see that eliminating titanium dioxide has a greater effect than doubling the amount of stain in the glaze. The texture of this tile is also ideal, and will be the base for developing a red crater glaze.