Jennifer Baumeister on thu 23 dec 04
What I did was first was to add bentonite ( 2 %, slaked and mixed into glaze , then whizzed with handblender, let sit for 12 hrs, re whizzed and put through sieve. ) This made no apparent effect other than the watery part of the glaze became more skim milk like. The solids in the glaze went through the screen and straight to the bottom of the
bucket.
Next I tried the Epsom salts. Added a tbsp to a cup of hot water. Whoooosh, The instant that the mixture hit the glaze it turned back to a normal creamy suspended consistency, like magic . I did not add all of the Epsom water, probably about a 1/4 cup.
The glaze had indeed deflocculated. As to why , I'm not sure yet but plan to learn more about my materials.
.....Is it possible that whizzing with a hand blender could deflocculated a glaze...(if you over whip some things in cooking , they can separate ...) ?
For consistency, I use demineralized water ( reverse osmosis ) for glaze mixing . My buckets were newly acquired and may have had some contaminate in them ( restaurant buckets ),I used 2 buckets when mixing back and forth.
I have fired with the fixed glaze and It has turned out "normal"... ( even reglazed a couple of the pieces that had messed up before the fix ,they turned out also.
For better understanding of the materials and their reactions to each other ,John Brit recommended The Potter's Dictionary of Materials and Techniques.
I lucked out , My Hubby , who always waits until we are in a hourly countdown to xmas before thinking he should shop or something, asked what I would like...
The dictionary is on rush order an may even make it by tomorrow !!
I am very excited, after looking at teasers for the dictionary on the internet, it looks like it is exactly what I need to help wrap my brain around glaze materials and their formulation.
I'm a slow learner, I've been doing nothing but read glaze books for the last year and I feel like I have retained
less than 1%, but at least I now almost understand what is being talked about.
I wish someone had warned me when I got hooked on form (clay) that I would also have to become a chem. major, tool maker, web page builder, marketing expert, accountant, janitor , not to mention the time spent getting into shape in order to lift the 100's of kilo's of clay into the basement ! Grin....I love it !
( ...for those of you who missed the original post the glaze we are talking about is MC6 High Cal Semi 2 with rutile 6
copper carb 4 , cobalt .5. It turns out a lovely variegated green, and is absolutely gorgeous dipper over raw sienna ! )
For the next batch I mix up , I'm not sure whether to add bentonite or not... Perhaps I'll split the batch, half with and half without. We will see what happens. I will also check the acidity of the water , the jug says demineralized by reverse osmosis and ozonated ( whatever that means..., could it be ionized ? ). I also may have added a smaller amount of tap water to the glaze mix while adjusting the mix. I'll check the ph on that also .
Cheers,
Jen
Date: Wed, 22 Dec 2004 02:04:26 -0500
From: Ron Roy
Subject: Re: What happened to my beautiful green ?
Hi Jen,
I did not respond to your original post because I knew John would have
better advice - he works at cone 6 and I work at cone 10 - so he has the
experience.
If a glaze has too much water - it will settle out quickly - as John said -
I would take some water off and try it thicker.
Neph Sy can make glazes settle out quickly - but in this case there is only
4% and the raw clay is high - so I would not expect the problem.
If - however - the water you are using is acidic - then I would think
deflocculation might be a problem - and bentonite will help. You may want
to use deionized water (or distilled) next time you mix this glaze
The advice about Epsom salts is also worth exploring - just melt a couple
of table spoons in a cup of water - make sure it's dissolved - a microwave
is a fast way to do it - just keep applying the heat till you can't see any
more crystals - but don't let it boil over.
Lets say you have a 5 gallon bucket of glaze - add one teaspoon of Ephesian
solution - stir - wait for 10 min - stir again. If the glaze thickens a bit
that may be all you need - the trick is to add it a little at a time - too
much and the problem gets worse by the way.
It is possible that the copper carb is processed with other chemicals -
they may still be present - and may be causing the problem - if that is the
case you can try "washing" it before you use it - use hot water and the
copper oxide or carbonate to it - when it settles out pour off the water -
do that a couple of times - to just the right amount of copper called for
in the glaze - that will lower the amount of any problematic solubles in
the copper - you can then just add it to your glaze before sieving.
Let us know if any of the suggested solutions work - we can all learn from
your experiments.
RR
>Thank you to everyone who responded to my questions.
>I'll give the fixits a try. Luckily I had only made a 1500 gram batch.
>
>Are there certain material combinations that cause this phenomena (
>deflocculated )?
>
>I have used the MC6 High Cal semi mat base with other combinations and
>have not had this problem..
>( I am assuming it has something to do with the copper )
>
>Is there anyway to predict "fall out" using the unity data for any given
>recipe ?
>
>Wishing everyone Happy Holidays ,
>Jen
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