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Tamas

Hard Crystals Developing In Glaze Slurry

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First of all, hello everyone, I am a hobby potter living in the UK, very much in the learning phase still. This is a great forum with a wealth of information, I hope I will be able to contribute, and not just ask silly questions.

 

So let's start right away with the first silly question:) The other day I mixed some Caramel Candy glaze for testing. The glaze recipe is here:

 

https://glazy.org/recipes/6131

 

After a few weeks when I opened the container I saw that hard crystals had developed in the glaze slurry, the size of small pebbles. Which component is responsible for this, and how can one prevent this from happening?

 

Thank you.

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Probably the sodium, possibly the lithium. 

 

How to prevent it is another matter.  Occasional mixing at regular intervals might help to disturb crystal growth but not sure.  This very occasionally happens in my glazes as well.

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What is the shape of these "pebbles"? Are they clearly little crystals with flat faces and nice edges and corners? If so, they are lithium crystals precipitating out from the lithium carbonate in the recipe. I have found these commonly when a glaze slurry has been left sitting for a while, particularly when there has been a temperature decrease in an unheated area. The solution (pun intended) is to sieve out the crystals and put them all in a small glass container with a small amount of the glaze slurry (enough to cover) and heat it in a microwave oven until the crystals dissolve again. Then stir it back into the glaze. You do not want to discard the lithium crystals because the lithium in them is a necessary flux in the glaze.

D.M.Ernst and Tamas like this

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I have realized I never reported back. The solution you proposed has worked - heating the glaze has indeed dissolved the crystals and it became usable again. Thanks!

D.M.Ernst likes this

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if you have a mortar and pestle, sieve the glaze, use the m and P to grind up the crystals, add the powder to the glaze, sieve again and add again. hopefully you can get enough to retain the quality of the glaze.

The microwave action sounds easier.

 

Marcia

Tamas likes this

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