Wendy Kelsey on wed 31 may 06
I know I should make my own glazes but I have a stash of
commercial glazes that are semi-transparent that I would
like to make opaque. What product do you suggest I add - I
see there are quite a few chemical products listed as
adding opacity but I don't know which one to choose.
Any ideas as to quantity to add also would be appreciated
although I know experiment is the key?
Thanks all for your help.
Wendy Kelsey
Operations Manager
Martini Ceramics
Custom Tile and Ceramic Arts
1272 Paradise Cove
Ferndale, WA 98248-9469
Telephone: 360-392-8607
Fax: 832-550-4856
Bob Masta on thu 1 jun 06
Wendy:
When making glazes from scratch, it's not unusual to add
10 to 15% zircopax by dry weight to get opacity. If your
commerical glazes are dry powders, the you might try
5, 10, and 15% tests to get the lay of the land. If they
are premixed with water its a little tougher. I'd use a
crude assumption that half of the weight is water, and
try 2.5, 5, and 7.5% of the wet weight just to get started.
However, I suspect you will be unhappy with the results.
You will notice that as they get more opaque, the glazes
will also get whiter. You may end up losing most of the
color you are used to. Th reason is that when a glaze
is trasparent/translucent, you can see all the color
all the way through the thickness of the glaze. But when
a glaze is opaque, that very opacity blocks all the color
except that on the very surface. If you start trying to get
that color back by adding more coloring oxides, you
may end up needing rather large amounts... sometimes
so large that they change the character of the glaze.
As an alternative, you might consider keeping the glazes
just as they are, and putting down an opaque white slip or engobe
first.
Best regards,
Bob Masta
--------------------------------
Wendy Kelsey wrote:
>
> I know I should make my own glazes but I have a stash of
> commercial glazes that are semi-transparent that I would
> like to make opaque. What product do you suggest I add -
> I
> see there are quite a few chemical products listed as
> adding opacity but I don't know which one to choose.
>
> Any ideas as to quantity to add also would be appreciated
> although I know experiment is the key?
>
> Thanks all for your help.
>
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