|Monthly Tech-Tip |
Modified: 2021-04-20 12:48:32
An amber-colored glaze that produces a clean, micro-bubble-free transparent glass. Works well on brown and red burning stonewares.
|Alberta Slip 1000F Roasted||40.00|
|Ferro Frit 3195||20.00|
An alternative recipe to GA6-A (this uses Ferro Frit 3195 instead of 3134). It fires to a more brilliant glossy surface.
This fires to a lower thermal expansion (by virtue of higher B2O3, Al2O3 and SiO2 levels) so will solve crazing issues on most bodies on which the GA6-A version crazes.
The chemistry in this is not compatible with the rutile blue version (see picture below).
This one also does not crystallize on slow cooling.
The difference is a slow-cool firing. Both mugs are Plainsman M340 and have a black engobe inside and partway down on the outside. Both were dip-glazed with the GA6-B amber transparent and fired to cone 6. The one on the right was fired using the PLC6DS drop-and-hold schedule. That eliminated any blisters, but some pinholes remained. The one on the left was fired using the C6DHSC slow-cool schedule. That differs in one way: It cools at 150F/hr from 2100F to 1400F (as opposed to a free-fall). It is amazing how much this improves the brilliance and surface quality (not fully indicated by this photo, the mug on the left is much better).
Glaze is GA6-B Alberta Slip rutile blue base. Fired at cone 6. The "Mother Nature's porcelain". from which this piece is made, has 6% Mason 6600 black stain. This glaze is an amber transparent and on the black porcelain produces a blacker deeper color than a typical transparent would.
Hand built. Cone 6 drop-and-hold PLC6DS firing. The engobe is the L3954B base recipe with added Mason 6600 black stain, it was applied at the leather hard stage inside and part way down the outside. The GA6-B glaze enhances the black under it. By Tony Hansen.
Fired at cone 6 using the C6DHSC schedule. On Plainsman M340 and Buffstone. Left: Alberta slip with 20% Ferro frit 3195 (GA6-B). Right: Alberta Slip with 20% Fusion Frit FZ-16 (G3903). This Fusion zinc frit is a super-melter, much better than 3195. A picture cannot do this glaze surface justice! The zinc brings out the red coloration much better. Frit FZ-16 is not readily available, we are hoping companies will eventually stock it. And it produces a more brilliant glassy surface that highlights thickness variations even better. Adding a little extra iron oxide (e.g. 1-2%) would make the effect even richer.
Fired to cone 6 using the C6DHSC schedule. Top: GA6-B. This recipe is 80% Alberta slip and 20% Ferro Frit 3195 (we used to use frit 3134 but have found frit 3195 works much better). Bottom: We added 1, 2, 3 and 4% iron oxide. At about 2%, the color matches the rich reddish effect you would get if you used an 80:20 Albany:3195 recipe (without an iron addition). An added benefit is that the iron acts as a fining agent to remove micro-bubbles to achieve better transparency.
Making black using metal oxides normally involves cobalt oxide, manganese dioxide, copper oxide and iron oxide. Combined they typically comprise 10-15% of the recipe. Using the Alberta Slip GA6-B base recipe, only 4% Mason 6600 black stain is needed to get a jet black! These blacks were applied in varying thickness on a porcelain and buff stoneware before having the white second layer applied. The black glaze on the top-right tile only has 3% stain. The overglaze is a gloss white with increasing amounts of tin oxide added (4-7%). Beyond 5% there appears to be no advantage.
GA6-A - Alberta Slip Cone 6 Amber Base Glaze
An amber-colored glaze that produces a clean, micro bubble free transparent glass on brown and red burning stonewares.
L3500E - Alberta Slip Cone 6 Amber Base 3 - Low Expansion
An amber-colored glaze that produces a clean, micro-bubble-free transparent glass for use when GA6-B crazes.
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