ronnie beezer on mon 29 dec 03
Happy and Healthy New Year to all.
I need your help on mixing commercially made glazes. I purchased dry mixed glazes from our local ceramic supply place and some from Laguna Clay Co. I purchased 25 Lbs and 10 Lbs of various colors and would like to make 5 and 3 gallons for dipping. I've only done this once before and some of the glazes after they sat for a couple of days get hard and clumpy in the bottom of the bucket and it is extremely difficult to stir, then some from the same supplier stir very easily. Laguna told me that I need to add Bentonite to the dry mix to avoid this. I'm unclear on the exact amount I should use since one salesperson told me it is not necessary to use and another told me 114grms. Can you tell me how much Bentonite do I add to 25 and 10 Lbs? Can I add the Bentonite to already mixed liguid glazes? also since some glazes from the local supplier were OK, I don't know if the Bentonite was added to some but not all of the glazes I just purchased, will anything happen to the glaze if I add
the Bentonite regardless if it already has been added?
Thanks for your imput.
Ronnie
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Dave Finkelnburg on mon 29 dec 03
Dear Ronnie,
Depending on how much clay, especially ball clay, is in the commercial
glaze, you need none, some or a lot of bentonite. :-) The more clay, the
less bentonite is needed.
The best thing to do is mix, in correct proportions, about 100 grams of
dry glaze in water, let it sit a couple days, then see what it is like. If
it settles rock hard, then do the same test but first add 2 grams of
bentonite (2%). The easiest way to do this is to add the bentonite to the
dry glaze in a jar you can seal tightly, and then shake it up good, then
pour it into the water and let it just sit there overnight, then mix and
screen. For glazes you want to suspend a little, add 1/2-percent bentonite.
In between, add more. You really don't want to go much over 2%, though, or
you'll have problems with the glaze not drying or shrinking too much.
Because of that, I would NOT just add bentonite to any glaze without
testing the glaze first.
Once you determine how much bentonite to add to a particular commercial
glaze, write that down in your studio notebook where you can find the
information the next time you need to make up a batch. And, knowing the
percentage, you can figure how much to add to 10 or 25 pounds or any other
amount of dry glaze mix.
Good glazing!
Dave Finkelnburg, just in from cross country skiing in gale-force
winds in Idaho...
----- Original Message -----
From: "ronnie beezer"
Sent: Monday, December 29, 2003 8:11 AM
> I need your help on mixing commercially made glazes. .
Snail Scott on tue 30 dec 03
At 07:11 AM 12/29/03 -0800, you wrote:
>...dry mixed glazes...get hard and clumpy in the bottom of the
bucket...how much Bentonite do I add...?
Some glazes (as you've observed) settle more than
others. For the ones that don't settle much at all,
leave them alone. Of the ones that do, add 1% of
bentonite (1% of the dry glaze weight before mixing).
Then see how it does. Some glaze may require 2%,
but don't start with that much; wait and see if it's
needed before adding that much.
You can add bentonite to either wet or dry glaze.
If adding to dry, dry-mix the powder before adding
water so you don't get jello-like lumps. If adding
to wet glaze, sift it lightly into the glaze while
mixing vigorously. You can also mix the bentonite
into water before adding to the wet glaze, but that
can add up to a lot of water to get it past the
'jello' phase, so I'd only do that if there's still
room left in your bucket.
Adding while dry is the easiest, but naturally
requires some previous experience with the glaze to
know how much to add. I'd mix just a small batch
(100-200 grams) to start - that'll be enough to
tell you whether it tends to settle, and test how
much bentonite is optimum. Then, mix the needed
amount into the dry glaze before making up the full
batch.
-Snail
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