I went to glaze some pots the other day only to find that my glazes had settled like a rock at the bottom of the buckets. I spent an hour painstakingly scraping the glaze only to have it re-settle a few minutes later. I found an excellent article written by Pete Pinnel addressing this problem.
To paraphrase the article, Pete begins by explaining that glazes are made up of many different sizes of particles. Under a microscope, the large ones looks like boulders and the smaller ones look like flat hexagonal platelets. The platelets like to hook together to form "flocs" that slow the boulder-like particles from sinking to the bottom. A glaze that is held in suspension by these flocs is called a flocculated glaze. Some materials that can cause a glaze to deflocculate are soda feldspar, nepheline syenite, wood ash, lithium carbonate and many common frits. I have a lot of soda feldspar in my base glaze, which explains the deflocculation.
The solution is to add a flocculant to the glaze. One common flocculant is epsom salts. I decided to try this option since it is cheap and readily available! I mixed a few teaspoon-fulls of epsom salts with hot water. I contined to add the epsom salt until no more would dissolve. I added this solution, a few teaspoon-fulls at a time to my glaze (trust me, a little goes a long way!) The glaze might thicken a bit, so it is OK to add more water. This worked like magic, and over a month later, my glaze still hasn't re-settled!
To paraphrase the article, Pete begins by explaining that glazes are made up of many different sizes of particles. Under a microscope, the large ones looks like boulders and the smaller ones look like flat hexagonal platelets. The platelets like to hook together to form "flocs" that slow the boulder-like particles from sinking to the bottom. A glaze that is held in suspension by these flocs is called a flocculated glaze. Some materials that can cause a glaze to deflocculate are soda feldspar, nepheline syenite, wood ash, lithium carbonate and many common frits. I have a lot of soda feldspar in my base glaze, which explains the deflocculation.
The solution is to add a flocculant to the glaze. One common flocculant is epsom salts. I decided to try this option since it is cheap and readily available! I mixed a few teaspoon-fulls of epsom salts with hot water. I contined to add the epsom salt until no more would dissolve. I added this solution, a few teaspoon-fulls at a time to my glaze (trust me, a little goes a long way!) The glaze might thicken a bit, so it is OK to add more water. This worked like magic, and over a month later, my glaze still hasn't re-settled!
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