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G2926B Cone 6 Transparent Whiteware Base Glaze

Description

For Whitewares, Porcelains

Intended for use on M370. It has the lower thermal expansion necessary to fit (without crazing). It sources boron from a frit instead of troublesome Gerstley Borate (you need to see and use this side-by-side with a Gerstley Borate based glaze to appreciate how much better this is). This recipe has good suspension and very good application properties (if it is mixed to the correct consistency).

G2926B Whiteware transparent with various stain additions on a porcelain body. It does not work as well as the G2916F Transparent for chrome-tin stains.

Firing

It is standard practice to fire cone 6 using a hold (or soak) at top temperature schedule (e.g. for 30 minutes) to produce a defect-free glaze. However we recommend a drop-and-hold firing schedule (like PLC6DS). Both require manual programming of your kiln (because none of the built-in programs do any kind of hold). If you have not manually programmed your kiln, this is a barrier you need to cross to produce more defect-free glaze surfaces.

Recipe

The recipe of this glaze is open-source. We developed it and sell it premixed but you can batch it (or even adjust it) yourself. For detailed technical information its page at the Digitalfire Reference Library by clicking the following: G2926B.

Adding the Stains and Opacifiers: Simply multiply the weight of the amount of powder you want to use and divide by 100. For example, if you have 2000 grams of glaze powder and want to add 6% stain: 2000*6/100=120 grams of stain. Or, 10% zircopax: 2000*10/100=200 grams of zircopax (stain %'s are suggestions, for some colors you may need more, testing is needed). Bright colors and whites will be muted on dark-burning bodies.

Crazing? If this crazes, perhaps on P300, we do have an alternative recipe, G2926S, that lowers thermal expansion. It utilizes a low expansion frit (either Ferro 3249 or Fusion F-69).

The story of two transparent base glazes. The inside one is our standard recipe. It is durable, glossy, clear and fits most bodies. It can be colored with stains, opacified and variegated. But it does not produce the brilliant metallic green when copper oxide is added. For that we recommend base base having high melt fluidity (it melts more), G3806C.

Mixing Instructions

For a one-coat dipping glaze we recommend a specific gravity of 1.44 (multiply the total weight of powder by 1.04 to determine the amount of water). Yield is about 1.4 litres per kg of dry powder. To prepare it for use as a single layer dipping glaze, add the powder to 90% of the water and mix until it flows well. Then adjust the amount of water to get the right specific gravity (more water to lower it). If needed, adjust the viscosity to prepare for sieving through 80 mesh. If the slurry is thin, there is a danger of it settling out while sieving, so it must be gelled. To do that add enough flocculant (vinegar, epsom salts) so that the slurry mass stops motion in about 5 seconds after mixing or stirring is ceased. Flocculants are powerful, only a few drops of vinegar (or pinches of crushed epsom salts) per gallon are needed.

After sieving do a final viscosity adjustment to make the slurry thixotropic (thixotropic liquids gel after motion stops). You can "see" the slurry thixotropy by noting a "bounce-back" on final stop-motion after stirring. Add enough flocculant to get stop-motion in around 2 seconds (in a 1-2 gallon bucket). As before, be careful in adding the flocculant, it is easy to add too much and get a bucket of jelly (if that happens add (by the drop) Darvan to re-thin it). When the slurry is right, you can two-second-dip a piece and on withdrawal it will drain well, gel quickly, only a few drips will fall and on turn-over the glaze will not run back down. It will apply in an even layer on dense or porous bisque. This "rheological state" of the glaze slurry can change on storage so be ready to adjust it later. Recheck the specific gravity from time to time and, if needed, adjust by adding or removing water.

As you gain confidence with doing this you will be able to create a thixotropic slurry at a range of specific gravities. Our recommended specific gravity is based on how much water is needed to get the undeflocculated glaze to a state where it needs about 2 grams of epsom salts per gallon to gel.

This can also be mixed as a brushing glaze or a first-coat dipping glaze.

Gallery

Underglazes with M370 and G2926B transparent. The colors were airbrushed and the clear glaze was sprayed over top.

L3954A white engobe on M340 and M390. The engobe has been applied to the inside and wrapped over the rim to midway down the outside. The clear glaze on the inside is G2926B Whiteware transparent. The outside glaze on the right is that same clear with 4% added iron oxide. The outside glaze on the left mug is GA6-A Alberta Slip clear using Ferro Frit 3195 as the flux.

Polar Ice with a G2926B clear glaze fired at cone 6. Notice the translucency.

These Coffee clay mugs have been white L3954B engobed at leather hard stage on the insides (the center one partway down the outside). After bisque the left and right ones were white-glazed on the inside (using G2926B+10 Zircopax). The one on the right has GA6-A (Frit 3195 version) on the outside (the center mug inside and out). The GA6-A over the black clay produces a very deep, rich ultra-gloss surface. The mug on the left has Ravenscrag floating blue (GR6-E) on the outside (producing a very right color over the Coffee clay).

Safety Data Sheet

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Logo Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508
Email: plainsman@telus.net