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Shawn Watt 07-24-2017 03:57 PM

potash base glass
I have been reading a lot about how potassium rich glasses typically show brighter colors. So I am interested in creating a potash base glass for some colors. Could anyone give me some general percentages for me to get started with? much appreciated.

Pete VanderLaan 07-24-2017 05:08 PM

Maintain your normal max alkaline flux at 18 %. Make about five to six percent of that Potassium Carb or Potassium hydroxide if you don't want all the oxygen. It should be sufficient and will greatly enhance color with selenium, manganese and nickel.
It does increase the viscosity of the glass but at the same time greatly increases the luster. If you can replace calcium with Zinc, you have an excellent base for cadmium selenium reds.
You could likely increase the potassium and cut down on the soda and I would be interested in your color tests as you go up. Potash is expensive stuff compared to sodium so reality beckons to get you to use both. Now if you can get the calcium out completely replaced by barium you will get a profoundly brilliant glass that polishes like a dream and makes copper blues gorgeous. This would not work out that well making the reds. My clear base is a potash barium glass . Jim Myers at East Bay Batch will mix it for you in Oakland. Spruce Pine has indicated that they don't want to stock potassium products which makes it really hard. I won't replace with sodium.

If you haven't stored Potassium carb before, when you get your bag in, immediately take it out and put it in zip lok bags or it will start to take on moisture from the air. Don't store the bags on the ground, get them up on pallets and that's true f most of the forming chemicals. The difference in temp from a cool floor and a warm air, and vice versa make for condensation which really messes up the materials.

Shawn Watt 07-25-2017 05:49 PM

Thank you Pete.

Shawn Watt 07-30-2017 03:22 PM

so where do you get the potassium hydroxide? All I can really find is the flake form and I imagine that wont mix very well.

Pete VanderLaan 07-30-2017 07:16 PM

KOH and it is indeed available as a crystal. To the point where the dealer in Providence insists that potassium carbonate doesn't exist.
I don't think it s critical to have. Dudley was always peculiar in wanting it but you can overwhelm the carbonate with stannous oxide without breaking a sweat. I don't stock it and he keeps trying to sell me his. Any of the potassium compounds are going to be hydrophilic so you have to get them away from humidity. Either use zip locs or air condition the storage shed.

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