Craig Martell on tue 6 mar 07
Hi glaze slakers:
I would have to parrot John's response and also say that it's not necessary
to slake a glaze overnight. I use a jiffy mixer and usually do a 5 gallon
batch at a time.
I am pretty careful to control the density of the glaze suspension by
adding X amount of water per gram of solids. So, if I'm going to mix a 5
gallon batch I will use 10,000 grams of the raw materials to 10,000 ml of
water. When this ratio of water to solids is used you get some interesting
insights on different glazes and how they suspend differently and also how
the glaze flows and applies. I was noticing when I changed the iron, in
one of the tenmokus that I use, how much thicker and flow resistant the
glaze was due to the finer, purer iron particles. I always check the glaze
by pint weight and not hydrometer and it was the same weight as before the
iron change. So, to get the flow and movement that I wanted, I added
several drops of Darvan, a deflocculant, until things were right. I didn't
want to add more water because that would dilute the suspension. I've
dealt with this ad nauseum with ash glazes. One thing that I don't like
when a glaze has too much resistance to flow is that it's harder for the
wax resist to resist, if you will. The glaze has a tendency to adhere to
itself and won't break and flow off the waxed areas. This is especially
true with glazes containing ball clay and other very fine particles. There
are electrical charges that enter into this too. If the glaze is too fluid
after mixing a 1gram solid to 1ml water ratio you can add drops of a
saturated epsom salt solution until the glaze "sets" and is again the
consistency that suits you and applies as you want it to.
The other thing that I factor in mentally is that different materials are
different molecular weights and particle size and this will vary the number
of molecules per/ml of water. I don't do anything or get real concerned
about. I just make a mental note of it.
So, I add the given amount of water in millilitres first and then add the
clay and vee gum(or whatever suspender is used) then blunge that until it's
pretty homogenous. Next I add the rest of the solids and let that glaze
hydrate while I mix other glazes and colorants. When I'm finished weighing
and measuring everything I reblunge all the glazes and sieve them a couple
of times thru a 100 mesh screen. The ash glazes are ball milled for an
hour to grind the ash and then I dump the charge thru a 100 mesh into the
glaze bucket and that's it.
regards, Craig Martell Hopewell, Oregon
Lee Love on wed 7 mar 07
If you are working with non-industrial, non-refined materials,
slaking is essential. For example, my Amakusa stone is not a powder,
but is often in large, hard chunks that don't break up even with my
heavy duty drill mixer. But, after sitting overnight, these chucks
become soft.
It is also essential for mixing glazes by the wet ladle measure,
to get consistent results. With ash glazes, it saves time because
you do not have to dry the ash before measuring. You just use the
washed ash slurry.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
| |
|
