Titanium instead of rutile for floating blue

Rutile blue glazes are actually titanium blues (because rutile mineral is an impure source of TiO2 and Fe₂O₃). The iron and titanium in the rutile react to form the floating blue effect. The GA6-C recipe has always relied on a 4% rutile addition. Its GA6-A base recipe contains significant iron (because of the 80% Alberta Slip), so could titanium oxide deliver the same floating blue effect? Yes.

These mugs are M390 clay. The top left one is the standard GA6-C (with rutile) fired using the C6DHSC slow-cool firing schedule (the bottom left normal cool PLC6DS schedule produces little color). But the ones on the right switch the 4% rutile for titanium dioxide (the L4655 recipe). The top right was fired using the slow cool, the bottom right was the normal cool schedule.

Titanium thus seems more consistent and reliable material than rutile. An excellent blue color is produced even without a slow cool (lower right).

Related Pictures

Rutile blue cone 6 glaze: Fast vs slow cool firing

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Same clay body: Plainsman Coffee Clay. Same glaze: MA6-C rutile blue. But the mug on the left was fired in the PLC6DS schedule (normally that one does not produce this much blue, but the heavily pigmented clay brings it out). The one on the right was fired in the C6DHSC schedule. That schedule also improves the gloss and surface quality of the inside GA6-B liner glaze.

Crystallization of this glaze gives insight into why it can host the floating blue effect

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These two mugs have the Alberta Slip base cone 6 GA6-A glaze on the inside and GA6-C on the outside (it just adds rutile to GA6-A). The left one was cooled normally (kiln off at cone 6 after soak). For the mug on the right, the kiln was soaked for half an hour at 1800F on the way down to develop the rutile blue glaze on the outside. But during this period crystallization occurred on the inside also. This provides an insight into my this GA6-A base hosts floating blue effects but GA6-B does not: The amount of Al₂O₃ is much lower, that improves melt fluidity and acts as a catalyst for crystallization.

Amaco PC-20 vs Ravenscrag Floating blues

They have advantages over the original recipe

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G2917, which I mixed as a brushing glaze, is on the right. This is not sold in jars, I make my own labels to demonstrate that DIY brushing glazes are not only possible, but can be better. I make the labels by ink-jetting onto regular paper, cutting them 62mm wide (2 7/16") and holding them securely in place using 2 7/8" transparent packing tape. The G2917 glaze is less melt-runny than typical floating blues. It contains the standard rutile/iron addition and exhibits good variation between thick and thinner applications. It also adds a little cobalt to ensure a good blue color no matter how the kiln cools. When I want more of the floating white colouration, I use the L4655 Alberta Slip floating blue recipe (left). Strangely, it contains no rutile, iron or even cobalt - it employs titanium dioxide (using iron available in the body and slow cooling as the mechanism of the blue). Both recipes have a big advantage over the original G2826R recipe from 50 years ago: they don't contain any Gerstley Borate, so the slurries don't turn to jelly in the bucket, this creates the option of mixing them as thixotropic dipping glazes

Videos

Links

Materials	Rutile A raw TiO2-containing mineral used in ceramics to color and variegate glaze surfaces.
Materials	Titanium Dioxide A super white powder used in ceramic glazes to variegate, opacify and moderate color.
URLs	https://insight-live.com/insight/share.php?z=oLZXQTy9TR Floating Blue - Substituting Gerstley Borate The original floating blue recipe shown side-by-side with variations made using frits instead of Gerstley Borate (and titanium and iron instead of rutile).
Typecodes	Floating Blue A popular cone 6 glaze that employed Gerstley Borate, it was very troublesome to use and to fire. Much work has been done to create alternative recipes.
Glossary	Rutile Blue Glazes A type of ceramic glaze in which the surface variegates and crystallizes on cooling in the presence of titanium and iron (usually sourced by rutile)

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