Enhance the G1947U Cone 10R Transparent Base Glaze

Project Name

Develop a Better Cone 10R Transparent

Project Codenumber

UnAssigned

Notes

G1947U was developed from a transparent glaze original used for porcelain insulator manufacture. To create G1947U I changed that recipe to source CaO from wollastonite instead of calcium carbonate and added a little zinc to start melting earlier.

Over time it has become evident that G1947U is not as transparent as it could be (because of suspended microbubbles and likely unmelted grains of quartz). That is why this does not work well for underglaze decoration.

Switching to Grolleg or New Zealand kaolin has proven to give whiter results on white burning porcelains.

We have traditionally used 200 mesh silica, it seems logical 400 mesh would result in fewer undissolved particles (and better clarity). Fully dissolved SiO2 would lower thermal expansion and increase durability.

Sourcing KNaO and some of the CaO, Al2O3 and SiO2 from a frit should improve melt flow and produce a glass better able to dissolve quartz, pass gas bubbles and level to an ultra gloss. The little B2O3 it brings will give "a kick" to the melting process. A possible issue will be solubility in the frits causing rheology instabilities.

G1947U does craze on some bodies, so I believe it would benefit from a reduced thermal expansion. That will come from changes above, but would move down even more by trading a little of the CaO for MgO and increasing the SiO2. Both of these would otherwise impede melting, but the measures taken above to improve it should easily accommodate this.

G3910 has been done and produced excellent results. Now we are ready for G3910A.

Cone 10R Transparent Base

Total:100.00

Auto Unity Formula + Mole%

Notes

*This glaze can be used in oxidation or reduction for a crystal clear. It works well in reduction on whiteware bodies like Plainsman P580 and P590 and is also good on all other high temperature stonewares (even iron reduction).

Add Zircopax (up to 15%) for white, and stains for colors as desired. Colors however will be more subdued than at lower temperatures and some, such as chrome-tin pinks, may not work at all.

Add 2-15% iron for a whole range of celadon, brown crystal, tenmoku, kaki, translucent brown and crystaline glazes. About 11% is good for a tenmoku. If the iron fluxes the glaze too much, remove the zinc.

This glaze has been tested in high temperature oxidation and produces the same glossy transparent. However, on stoneware bodies with coarser particle sizes the surface can be slightly dimpled. It does not seem to make a difference whether the zinc is removed or not.

Some stains that work very well at this tempature are mason stains no. 6242,6464,6305,6319,6364,6134, and 14k139. I found it was better to apply the stain over the glaze then under.

Pictures

G1947U Cone 10R Transparent Base glaze cone

On H550, H570 at cone 10R

On H550, H570 at cone 10R

On H450, P600 at cone 10 oxidation

On H450, P600 at cone 10 oxidation

Glaze cones fired in April 2012 con

Glaze cones fired in April 2012 cone 10R. kiln, shelf B6. Glaze cone clay is P700 P5797. The glaze cone on the left uses E.P.Kaolin for kaolin portion of recipe and glaze cone on right uses Grolleg Kaolin for kaolin portion of recipe.\nLooking to achieve \"bluish\" hue in color of glaze using the Grolleg Kaolin in glaze recipe instead of E.P.K. and is evident in photo this is confirmed. Color may be a little enhanced with light shade adjusted but this is being done to enhance what you can actually see in real life as there is a definite bluish hue to the Grolleg kaolin based recipe of this glaze.

1947U on Crystal Ice cone 10

Fritted version of G1947U #1

Total:120.00

Auto Unity Formula

Notes

*This changes G1947U as follows:
It sources KNaO from a frit
Using a calcined/raw kaolin combination
Switches ZnO for B2O3
Increases the SiO2

1500 powder, 1300 water.
Still very watery, had to add alot of epsom salts.

Melting much better. Much more transparent.

Pictures

G3910 ball melt test (vs. G1947U)

G3910 Transparent flow test (vs. G1947U)

G1947U, G3910 ON H443 AT CONE 10R

G1947U, G3910 ON H550 AT CONE 10R

The opacity in G1947U can really be noticed with side-by-side with G3910.

G1947U stains, G3910 does not

Felt pen, cleaned with acetone.

Cone 6 melt comparison G1947U/G3910

Cone 10ox comparison G3910/G3910

Fritted version of G1947U #2

Total:100.00

Auto Unity Formula

Notes

*Changes G3910 as follows:
Switch from EPK to Grolleg kaolin
Switch to 400 mesh silica
Increase silica to get better ultragloss and reduce thermal expansion.
Test this in cone 10 oxidation and reduction.

Pictures

Typecodes

ST-Untitled typecode

Alternate Code Number:GS10-C

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Fritted version of G1947U #2" id="188286" key="7xzPQqvr" date="2020-12-24" typecodes="ST" codenum="G3910A" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3110" amount="21.800"/> <recipeline material="Ferro Frit 3249" amount="3.600"/> <recipeline material="Grolleg Kaolin" amount="25.900"/> <recipeline material="Silica 400 mesh" lookup="Silica" amount="32.100"/> <recipeline material="Wollastonite" amount="16.600"/> </recipelines> </recipe> </recipes>

Born: 1994-06-30, Modified: 2020-12-24 13:29:33