Craig Martell on mon 19 mar 07
Heidy was asking:
>What are the opinions about barium frits? I wonder why they are never
>mentionned on Clayart.
Hello Heidy:
I think there has been some discussion on barium frits in the past but I
can't remember any specific details.
I fire cone 10 reduction and I haven't used any barium frit for a long
time. Most of them contain elements, such as boron, that I don't need or
want in the glazes. Ferro used to make a frit, #3247, that was about 50%
barium plus alumina and silica only. This frit was very easy to calculate
into barium glazes. Ferro hasn't made this frit for almost 20 yrs I
think. I talked with one of their engineers in Los Angeles who told me
that it was too hard to grind so they subcontracted the grinding and the
subcontractor finally bailed out for the same reason. So it goes.
If you fire at cone 6 I think that some of the barium frits might work very
well since boron is sometimes quite essential to glazes at cone 6. Also,
barium and boron have a very strong effect on melt when combined at the
right ratio. They are said to form a eutectic but I don't have any solid
info on that. The problem with barium frits, or any other for that matter,
is calculating them into a glaze. A lot of people don't know how to do
this so they have someone else help them of just bag it all together.
Here's the big Caveat about barium frits. They are good for protecting the
potter from exposure to barium but one placed in a glaze and fired, they
dissociate under heat and the glaze can still leach barium if there isn't
sufficient alumina and silica to hold the barium under acid attack from
food. So, using a barium frit does not automatically make the glaze food
safe. It's just as dicey as using raw barium if you don't know how to
calculate the glazes molecular formula.
If a potter is going to use barium, the amount must be limited and the
other aspects of the glaze must be addressed and engineered so that you
will have ware that leaches very little or no (almost impossible) barium.
regards, Craig Martell Hopewell, Oregon
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