Majolica painting problem (cobalt paint recipe please ???)

Hello all,
I am a beginner and I have a problem.
I have been trying with several glaze formulas.
The commercial glaze (tin added) that I have now is beautiful.
I fire at about 1050 C.
Problem is the cobalt blue (Delft style) lines I want to paint.
Lines have round craters as if the cobalt splatters a little or pops
open whem melting.
I have used several percentages between 2 and 8% of cobalt to paint.
My paint: 100% clear glaze+8%cobalt oxide+a few drops glycerine+a few
drops water. I paint on top of the dried unfired tiles glaze and fire
the tile.
What is the problem????? can anybody give me a good paint recipe?????
Thanks, Nina

In article , Nina
wrote:

Hello all,
I am a beginner and I have a problem.
I have been trying with several glaze formulas.
The commercial glaze (tin added) that I have now is beautiful.
I fire at about 1050 C.
Problem is the cobalt blue (Delft style) lines I want to paint.
Lines have round craters as if the cobalt splatters a little or pops
open whem melting.
I have used several percentages between 2 and 8% of cobalt to paint.
My paint: 100% clear glaze+8%cobalt oxide+a few drops glycerine+a few
drops water. I paint on top of the dried unfired tiles glaze and fire
the tile.
What is the problem????? can anybody give me a good paint recipe?????
Thanks, Nina

Nina, you might try the cobalt with just water, or with water and a bit
of gerstley borate, I'd have to look up the percentages at the studio.
I usually eyeball the cobalt with some water. Cobalt tends to spit
like that, but it might be a problem with the clear glaze. Try a few
tests. Hope this helps.

Cea

"Nina" wrote in message
om...
Hello all,
I am a beginner and I have a problem.
I have been trying with several glaze formulas.
The commercial glaze (tin added) that I have now is beautiful.
I fire at about 1050 C.
Problem is the cobalt blue (Delft style) lines I want to paint.
Lines have round craters as if the cobalt splatters a little or pops
open whem melting.
I have used several percentages between 2 and 8% of cobalt to paint.
My paint: 100% clear glaze+8%cobalt oxide+a few drops glycerine+a few
drops water. I paint on top of the dried unfired tiles glaze and fire
the tile.
What is the problem????? can anybody give me a good paint recipe?????
Thanks, Nina

Are you using cobalt carbonate or cobalt oxide? I use just colbalt
carbonate mixed with water and have never had a problem with it (hard to see
because of the pink color... some vegetable food coloring might work to make
it more visible if that is necessary).

"Nina" wrote in message
om...
Hello all,
I am a beginner and I have a problem.
I have been trying with several glaze formulas.
The commercial glaze (tin added) that I have now is beautiful.
I fire at about 1050 C.
Problem is the cobalt blue (Delft style) lines I want to paint.
Lines have round craters as if the cobalt splatters a little or pops
open whem melting.
I have used several percentages between 2 and 8% of cobalt to paint.
My paint: 100% clear glaze+8%cobalt oxide+a few drops glycerine+a few
drops water. I paint on top of the dried unfired tiles glaze and fire
the tile.
What is the problem????? can anybody give me a good paint recipe?????
Thanks, Nina

From memory when I did majolica it was 50% colourant and 50% frit added with
water I can check it out for you. As someone else mentioned though I think
what you have to do is lots of testing. Test with cobalt carbonate and
oxide, test your coppers and magnesiums and irons etc at the same time alone
with commercial stains. Do them with glaze, with just frit, lots of testing
because every glaze and every kiln is different and so testing is always the
key. Remember also that majolica is not food safe, the colourants are not
tied into a glaze and therefore release oxides etc.
A