Glaze Mixing
Crystalline Glaze Forum Dialogue
Original Post by Phil Hamling
Replies by Terry Fallon, Bill Schran, Doris Macdonald, Chris Groat
I have been batching and ball milling my base glazes. I find this tedious. There
is a limit to the amount of material I can get in the jars. I think it does a
great job of mixing everything together and probably accomplishes some particle
size reduction. I don't know if this is really needed and wonder why I don't
batch in a 5 gallon bucket and mix it all together with a large drill mounted
mixer blade. Also there is the issue of does a "ballmiller" contaminate his or
her glaze with the mill and ball's chemistry. I don't believe contaiminating the
glaze is an issue if the mill is porcelain and the balls alumina, but think
steel balls could be problematic. Also if the colorants were added to the mill
batch will they contamiate the system and booger up the works for subsequent
batches?
On the topic of coloring oxide additions my first attempts involed stirring the
oxides into the base. I found that I didn't do a real good job of breaking up
and dispersing the agglomerates so I got pretty nasty streaking. I ordered some
sieves, but before they arrived mixed some more by combining the colorants with
a small amount of the base glaze and making a homogeneous paste using a spatula.
I then introduced it to the batch I was coloring and blended it in with a small
drill mounted mixer blade. It seemed to work fine - no streaking. I could see
the colorant paste being incorporated in the base and went until I could not see
coloration in the clear wall of the container from it.
Well I have the sieves now and envision using them as a sloppy mess.
Can I get everyone's feedback on this? What are the pros and cons of the methods
I describe above? What do you all commonly do?
I mix 200 to 300gram at a time. I weigh out all ingredients including colorants
and CMC.
This I add to my 3lb. ball mill, add 80ml. of boiling hot water to every 100mg.
of dry.
Two to three hours later I pour through a 40 sieve catch my ball bearings and
sieve again though an 80.
After reading about some of our ingredients silica, manganese to name just two,
I felt that any sort of dry mixing was out, since my workroom is in my house.
I use a stenciling brush with the sieves, and after ball milling there is really
nothing to push though.
I use what are called mini sieve they are no mess to use. Check out Axner
Pottery Supply for them. The ball mill has a heavy rubber can and cleans up like
a whistle.
If I mix a larger quantity of glaze (500 - 1000 grams), I'll weigh out the
ingredients, put into a plastic container with lid and store dry. I will give
the batch a short stir, then dry sieve twice, 30m then 60m screens. I then weigh
out a portion, usually 200 grams, add my colorants, add CMC gum solution, then
sieve through 60m then 80m screens. This is enough for a few small pots or a
couple larger ones.
If I'm doing tests, then I start with the 200 gram batch and continue from that
point.
FYI, most of my work is tests. I haven't found a single glaze that doesn't
deserve a bit more tweaking.
Have you tried a kitchen blender? I have an 8 cup blender that seems to mix
glazes very well with no adverse effects. When mixing a large batch for dipping,
I first do a rough mix with the drill-mounted mixer, then blend it in batches.
Much faster and through than screening.
I've only done it one way. I always use a sieve. For my test batches I run it through an 80 or 100 mesh test sieve. I usually use the back of a spoon to push it through the sieve. The other day I pushed the spoon all the way through the sieve and so I tried using the big sieve from my talisman rotary sieve. It worked equally well, and actually didn't make much of a mess. Before and after sieving I shake the glaze a lot to mix it. I never get streaking if I sieve
Zinc Silicate Crystalline Glaze Pottery, A chronicle of my recent progress, Phil Hamling