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Glaze Application - Cracks


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I have just poured the inside of a stoneware cylinder (test piece bisqued to 1000oC) with a transparent glaze that crawled horribly in a previous batch. This is a commercially mixed dipping glaze - very reliable by all accounts! Following advice here and elsewhere I let it stand and drew the excess water off the top. The glaze is now like pouring cream consistency. 100ml weighs 153g. I've poured the inside - about 3 seconds. As it dried the glaze cracked - see photo. What does this indicate? Can I just finger-sand it and dip the outside or am I destined for more disappointment?

 

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If the glaze cracked, it is going to crawl 95% of the time when you fire it. Unless it is really fluid. So it's probably best to scrap it and wash it and dry it.

 

To me it sounds like your glaze is too thick and creamy, even if its weight/ml is close to what you want, it sounds like you need to add Darvans in small amounts and stir until you can poor a cup and it not crack.

 

A few drops goes a long way. 

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No idea. I am sure others will weigh in that might have a better idea of what to do. I know I had a glaze with this issue, if I added water the color was to thin, but it was way to thick to dip/pour or spray. It had a lot of Gerstly Borate in it which made it absorb water like crazy. So I used Darvans to thin the glaze without adding more water. It worked brilliantly. You could try searching for deflocculant and see what comes up on the forums or google.

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Pouring cream consistency for a C06 bisque. May be way too thick.

I'd test a few tiles with measured added water quantities.

Then wipe out pot with damp sponge.

You don't have to test fire your tiles, go with the "thickness which doesn't crack on the tile dip test..or have you been there and such application is too"skinny" for the look you want?

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How I love this forum - wake up to find all this advice, it's great!

 

I washed off the old glaze last night. The pot is drying off in the airing cupboard. I added a small quantity of sodium silicate to my bucket of glaze.

 

First time round I did wipe the pot before pouring the inside - and NOW ....

I'll try dipping a test tile as you suggest Babs and will dampen the pot by wiping again before a second pouring attempt.

 

That means I've followed the advice of everyone above. Watch this space!

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