WoDo White Matte

None of the ingredients in this recipe are toxic; but to judge it's safety, one would need to know what temperature you would be firing and then it would have to be broken down to make sure it has enough alumina and silica to be a good, functional glaze. Also, if you intend to use colorants with this glaze, the colorants and amounts would have to be taken into consideration.

Regards, June

Hi June, Thanks for your speedy reply. I will be firing at ^5 to ^6. Right now I will be just testing the base recipe so I don't have any colorants percentages worked out yet. Some suggestions I have come across and would like to try are the following percentages:

This WoDo Matte is reported to be a waxy white. I would love to hear from others who may have tried it so I can get various opinions. I'll be trying it myself soon, one way or the other. My main concern was for any toxicity levels. I checked before I posted here, but want ed to hear from those more experienced. This will be my first self mixed glaze and I don't want to screw up right off the bat. Thanks so much, Gaye

That glaze is too low in silica, even for a cone 6 white glaze. The ratio of alumina and silica is only 4.33 which should be very matt, but because it's too low in silica, it winds up being a waxy surface because of the deficiency of silica. Here's a revision of it, bringing it up around the minimum of 2.5 moles of silica for cone 6. This will also greatly lower the expansion of the glaze which will lessen the possibility of badly crazing. The original has an expansion rate of 8.54 and this has an expansion rate of 7.47. The ratio of silica/alumina on the revised version is 6.61 which would make this a nice, smooth matt.

Perry C 6 Matt

Nepheline Syenite 39.8 dolomite 20.3 Wollastonite 4.9 OM #4 Ball Clay 16.3 Silica 18.7

If you want it more satiny, you can add 11 more grams of silica which will bring the ratio up to around 8 which will give a more satin finish. It will also help the expansion-- lowering it to 7.03. You might want to do a test of each, and then wet mix equal amount of each of them to get a third variation. Note, that when you add high amounts of iron, you risk running unless you up the alumina and silica. Iron is a very active flux and you have to compensate for that.

Regards, June

Thanks.

Deb R.

June, Thank you for your advice and revised recipe. I printed out your post. I appreciate you going through all that trouble. I plan to test both. Now, you've prompted another question...you said the recipe I posted was too low in silica and that's why it is waxy...I think I would like it waxy. That was part of what made me interested in the recipe. Do you think it would be foodsafe or, if I decide to use it, should I stay away from anything to do with food consumption? Thanks again. Gaye

snipped-for-privacy@aol.com (GaSeku) wrote in news: snipped-for-privacy@mb-m04.aol.com:

Gaye

Your glaze is not foodsafe.

It does not fall into the limits for a food safe glaze. You do not have enough silica to fully form a glass. To be food safe glazes need to be hard and shiny. Matt glazes are for decoration.

I have forwarded you a Matrix printout so you can visually see that it does not conform

John W

When a glaze is low in silica, the low silica keeps the glaze from forming a glassy structure which would hold coloring oxides in solution. When they aren't held in solution, then acidic foods, dishwasher soap, etc. can literally pull the oxides out of the glaze and at least wash the color out of the glaze and at worst, deposit potentially toxic oxides into the food. Matt glazes can be perfectly food safe. They just have to be properly formulated with and the right amounts of materials and alumina and silica for their temperature range to make a safe, balanced glaze. As far as flameware goes. It is something I would advise to shy away from, at least commercially. There have been a lot of law suits over flameware which is why you rarely see potters making it any more. You are very limited to the glazes you can use because to make the glazes fit the body, you need very low expansion glazes. The iron certainly can be part of the cause of the running, but in a properly formulated and fired glaze you can have high iron without running. It's all a matter of balancing the formula and the firing.

Regards, June

Excellent explanation June. Thanks! Gaye