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Adjusting the Thixotropy of an Engobe for Pottery

How to fine-tune the thixotropy of a ceramic engobe for pottery

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Transcript/Notes

Let’s adjust the thixotropy of an engobe for pottery.
I mixed this some time ago and have used it on several occasions. While it has gelled in storage notice how the mixer action quickly turns it into a fluid slurry, too fluid for my needs.
To achieve a gelling action in the 5 to 10 seconds that I need, I’ll add a pinch of Epsom salts, let it mix for a while and test to see how well it performs on a mug.
Hmmm. On pour-out it is evident that it is now gelling too quickly, not draining as well as it should staying on too thick by the handle.
It appears I have gelled it too much, something very easy to do.

more..

Fortunately, it can be thinned with a Darvan addition. But it’s super sensitive. I’ll add just one drop.
Now, it’s better, more fluid when I first draw the mug out. But then gelling before it can drain.
With another drop it’s better.

Engobe slurries are sensitive like this, requiring periodic adjustment.
Be determined. The ceramic tile industry uses thousands of tons of engobe a year, dealing with the this issue every day is just part of the process.

Links

Glossary	Engobe Engobes are high-clay slurries that are applied to leather hard or dry ceramics. They fire opaque and are used for functional or decorative purposes. They are formulated to match the firing shrinkage and thermal expansion of the body.
Glossary	Thixotropy Thixotropy is a property of ceramic slurries of high water content. Thixotropic suspensions flow when moving but gel after sitting (for a few moments more depending on application). This phenomenon is helpful in getting even, drip-free glaze coverage.

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