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Min

Member Since 31 Mar 2010
Offline Last Active Yesterday, 04:32 PM
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Posts I've Made

In Topic: Can A Glaze With A Higher Coe Have Less Crazing Than A Lower Coe?

Yesterday, 04:32 PM

Have you read this article: http://ceramicartsda...file-glaze-fit/

It says it more succinctly than I could. I like the tight pants versus baggy pants analogy.

 

For your flux, I would try one of the low expansion ones in place of the whiting. Magnesium from talc, dolomite, magnesium carb or lithium from spodumene, a lithium frit if you can get one in GB that's not to expensive, or even some lithium carb with some source of magnesium. Keep an eye on the alumina to silica ratio. I don't fire ^10 so hopefully someone else can chime in here and give you a hand with other suggestions. 


In Topic: Can A Glaze With A Higher Coe Have Less Crazing Than A Lower Coe?

Yesterday, 03:32 PM

 

 

I thought glaze should be under compression not the clay?

 

Oops, typo, thanks for catching that, I fixed it now.


In Topic: Can A Glaze With A Higher Coe Have Less Crazing Than A Lower Coe?

Yesterday, 01:55 PM

Couple things, do you have a gloss glaze that fits your body without crazing? If you do, what is it's COE (without colourants or opacifiers)? The silica to alumina ratio's suggest your tests are not gloss, COE figures don't work with matte glazes.

 

Did the tests come from the kiln crazed or did you put them through accelerated craze testing? Glaze thickness all the same?

 

Way too little silica in all those ones you tested to be durable plus the first one is really low in alumina also, the second quite low too. If these are the ingredients you want to play with maybe start with about 80 cornwall and 20 whiting but I think you will still get crazing.

 

To put the glaze under compression glaze should have an expansion that is slightly lower than the body but there is a risk of shivering when you do this too much.


In Topic: Clay Ph

Yesterday, 12:52 PM

Hi Babs, thanks for the thoughts. I think I will just have to calcine some OM4 and do some tests. Was hoping someone had a definitive answer but this is ceramics so I guess there rarely is one :)


In Topic: Alberta Slip Glaze

24 November 2014 - 12:12 PM

This is similar to Steve Slatin's Gnu Blue and the Alberta Slip Rutile Blue from Digitalfire. Pretty sure you can put the colour change down to your rutile if your clay, application method and firing schedule haven't changed.

 

From Digitalfire: http://digitalfire.c...html?logout=yes

Hansen says you can restore the blue colour by adding 0 point 25 cobalt ox. if you don't do the slow cool this glaze prefers.

 

If you have titanium dioxide you could try a test of that plus some iron to sub for the rutile. It's not going to be exact since rutile has other "dirty" ingredients in it but it might get you close. So for the 5 rutile in your recipe you would try titanium diox 4.5 and iron ox 0.5