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Glaze Making Issue

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#1 DMCosta


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Posted 16 July 2014 - 08:22 PM

Bare with me, I'm relatively new at glaze making...

I recently made 250g of a yellow-brown glaze, a grey-brown glaze, and a transparent. All low fire cone 04, all with the same base ingredients. They all fired very gritty and rough feeling, and lack any shine or 'glass like' look. The kiln fired properly I got the recipes from a reputable glaze book. I wanted to tweak the recipe to get them more shiny but what can I do? Will adding more silica/flint help? If so how much more to a 250g sample?

Thanks for your help

#2 Marcia Selsor

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Posted 16 July 2014 - 10:29 PM

you could try an small increase of silica line 1 or 2 % for starters
.or it could require a soaking at the maturing temperature during the firing.
Marcia Selsor, Professor Emerita,Montana State University-Billings

#3 ayjay


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Posted 17 July 2014 - 10:30 AM

 They all fired very gritty and rough feeling,


Did you sieve the glazes?

#4 neilestrick


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Posted 17 July 2014 - 10:53 AM

For batches that small, sieving can be difficult. A stick blender works really well for smoothing out small batches.

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#5 Bob Coyle

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Posted 17 July 2014 - 01:52 PM

The glaze might not have fluxed, or it may have a lot of un-dissolved material left in it which would also cause roughness.


For small batches of test glaze, I sieve the finished glaze through a standard 10 cup coffee filter basket. I use a 1 inch paint brush and swirl it around inside the filter basket to help force the glaze through the fine mesh. This way even the most stubborn lumps get blended in.  Any crud in the raw materials gets left in the basket.

#6 Pugaboo


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Posted 17 July 2014 - 05:52 PM

You can also buy a Talisman test sieve, it's small, comes in different mesh sizes and fits inside a small plastic container from the paint aisle. You can use a rib or a brush to work it through. I bought mine for making small batches of colored slip up so I can mix the mason stain in evenly but now that I am starting to test glazes find they work for that too. I don't have a stick blender yet will have to see if I can find a cheap one but until then the sieve seems to be working.

The world is but a canvas to the imagination - Henry David Thoreau

#7 DMCosta


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Posted 23 July 2014 - 07:51 PM

Thank you everyone for the advice, I did indeed sieve the glaze, I always do. Still perplexed about it, I may just ditch that recipe all together and move forward with something different. 

#8 Babs


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Posted 23 July 2014 - 08:31 PM

What was your thickness of application? Is your clay body a smooth one? Did you apply straight after mixing? Just wondering here.

What's the recipe?

#9 Wyndham


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Posted 24 July 2014 - 08:22 AM

Wollastinte and zinc oxide can harden in the bag over time, we need to see the recipe to help


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