glaze gone bad

Hi Everyone,
Can glazes go bad? I have a glaze that was real nice when it was new
(two years ago). Now it seems to have gone bad. The pots with this
glaze on them come out of the kiln with what looks like bubbles that
have formed and burst open but never smoothed over. All the other
pieces in the same load come out fine with different glazes. I fire to
cone 6 oxidation. No matter which clay I use, this particular glaze
has been unsuitable lately. It is laguna sage matte. Thanks to anyone
answering this question.
Sandi

"Red Deer" wrote in message
ps.com...
Hi Everyone,
Can glazes go bad?

Yes ... over time some ingredients of a glaze can get slowly dissolved in
the water. When the glaze is applied to the pot, the dissolved ingredient is
absorbed into the clay and out of the glaze mix. Hence, the glaze mix is no
longer complete, and all sorts of problems follow.

The solution is to dry the glaze out completely, grind it up and re-mix with
water ... or if that's too much trouble, just chuck it out and make a new
batch.

Cheers

Dave

On Sun, 1 Oct 2006 09:21:12 +1000, "David Coggins"
wrote:


"Red Deer" wrote in message
ups.com...
Hi Everyone,
Can glazes go bad?

Yes ... over time some ingredients of a glaze can get slowly dissolved in
the water. When the glaze is applied to the pot, the dissolved ingredient is
absorbed into the clay and out of the glaze mix. Hence, the glaze mix is no
longer complete, and all sorts of problems follow.

The solution is to dry the glaze out completely, grind it up and re-mix with
water ... or if that's too much trouble, just chuck it out and make a new
batch.


Hmm, I'd be really surprised if the dry-and-regrind changed anything.
if the problem is solubles. They'll probably redissolve immediately
the next time they see water. (They were originally bound to
something else in the glaze, but once they have become free salts
it will be just as though you had added the salts in the batch.)

But before you pitch the glaze, are you sure that it's completely
mixed? It's not uncommon for portions of a glaze to settle out
into a "hardpan" layer on the bottom of the container. (Remember,
glazes are just suspensions, not solutions, so settling is to be
expected.) If this is the case, you may be able to restore it just
by some vigorous mixing and sieving. If that doesn't do it, then
dry-and-regrind certainly would.

Another way glazes go bad is when there is some organic binder
present that deteriorates over time. I think this typically causes a
bad odor and/or discoloration, but there are lots of binder products
out there so maybe some aren't so obvious when they go bad.
At any rate, I don't know if this could cause your symptoms.

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

"Bob Masta" wrote in message
...
Hmm, I'd be really surprised if the dry-and-regrind changed anything.
if the problem is solubles. They'll probably redissolve immediately
the next time they see water. (They were originally bound to
something else in the glaze, but once they have become free salts
it will be just as though you had added the salts in the batch.)


I am no chemist, so I could well be wrong. Certainly if a frit or other
ingredient has broken down into base materials it will be a waste of time.

I understood that some glaze ingredients, although insoluble over the short
term, would very slowly dissolve into the water over a long period of time
(years). Supposedly these would be reclaimed if the glaze was dried and
reconstituted. Dry, regrind and remix was the recommendation from a large
premixed glaze manufacturer here in Australia (Cesco) - perhaps this applies
to fritted glazes only? I must admit that we have only rarely done this, as
the effort usually outweighs the cost of buying or making a new batch.

Cheers

Dave

On Mon, 2 Oct 2006 09:49:23 +1000, "David Coggins"
wrote:


"Bob Masta" wrote in message
...
Hmm, I'd be really surprised if the dry-and-regrind changed anything.
if the problem is solubles. They'll probably redissolve immediately
the next time they see water. (They were originally bound to
something else in the glaze, but once they have become free salts
it will be just as though you had added the salts in the batch.)


I am no chemist, so I could well be wrong. Certainly if a frit or other
ingredient has broken down into base materials it will be a waste of time.

I understood that some glaze ingredients, although insoluble over the short
term, would very slowly dissolve into the water over a long period of time
(years). Supposedly these would be reclaimed if the glaze was dried and
reconstituted. Dry, regrind and remix was the recommendation from a large
premixed glaze manufacturer here in Australia (Cesco) - perhaps this applies
to fritted glazes only? I must admit that we have only rarely done this, as
the effort usually outweighs the cost of buying or making a new batch.


I am no chemist either, but once the soluble is dissolved in the
water, drying out will surely just leave it as a powdered salt.
I would not expect it to be re-bound to the original minerals just by
drying together with them. What would most assuredly work (if
you were stranded on a desert island with only this glaze and your
kiln) would be to calcine the whole works into a do-it-yourself frit.

I wouldn't think a properly fritted glaze would ever release anything
much into solution... after all, the reason for making a frit in the
first place is to make sure those pesky solubles are no more... their
metals become part of the glass, and their carbonates, etc, are
driven off.

But I agree that it makes a lot more sense to just start over from
scratch, in most real-world situations.

Best regards,



Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

Red Deer wrote:
Hi Everyone,
Can glazes go bad? I have a glaze that was real nice when it was new
(two years ago). Now it seems to have gone bad. The pots with this
glaze on them come out of the kiln with what looks like bubbles that
have formed and burst open but never smoothed over. All the other
pieces in the same load come out fine with different glazes. I fire to
cone 6 oxidation. No matter which clay I use, this particular glaze
has been unsuitable lately. It is laguna sage matte. Thanks to anyone
answering this question.
Sandi - Hi - suggest if have glazes that are old, try firing a small sample first - save a pot!

Red Deer wrote:
Hi Everyone,
Can glazes go bad? I have a glaze that was real nice when it was new
(two years ago). Now it seems to have gone bad. The pots with this
glaze on them come out of the kiln with what looks like bubbles that
have formed and burst open but never smoothed over. All the other
pieces in the same load come out fine with different glazes. I fire to
cone 6 oxidation. No matter which clay I use, this particular glaze
has been unsuitable lately. It is laguna sage matte. Thanks to anyone
answering this question.
Sandi- Hi, suggest if glaze is old, try small sample fire on piece of clay first - save a pot!

Red Deer wrote:
Hi Everyone,
Can glazes go bad? I have a glaze that was real nice when it was new
(two years ago). Now it seems to have gone bad. The pots with this
glaze on them come out of the kiln with what looks like bubbles that
have formed and burst open but never smoothed over. All the other
pieces in the same load come out fine with different glazes. I fire to
cone 6 oxidation. No matter which clay I use, this particular glaze
has been unsuitable lately. It is laguna sage matte. Thanks to anyone
answering this question.
Sandi, (Australia) Suggest try firing small sample of old glazes first - save a pot!

David Coggins wrote:
"Red Deer" wrote in message
ps.com...
Hi Everyone,
Can glazes go bad?

Yes ... over time some ingredients of a glaze can get slowly dissolved in
the water. When the glaze is applied to the pot, the dissolved ingredient is
absorbed into the clay and out of the glaze mix. Hence, the glaze mix is no
longer complete, and all sorts of problems follow.

I was not aware of this. It leads me to ask a question.

I am in the habit of keeping 5 gallons of glaze. When the level in the
bucket goes down so much that it is hard to apply through dipping, I
mix more and add it in. Is it the case that I am susceptable to this
problem? I probably go through 5 gallons of my more popular glazes
once a year, but others can take longer.

Thanks,

Mark.

Hi Everyone,
Can glazes go bad?

Yes ... over time some ingredients of a glaze can get slowly dissolved in
the water. When the glaze is applied to the pot, the dissolved ingredient
is
absorbed into the clay and out of the glaze mix. Hence, the glaze mix is
no
longer complete, and all sorts of problems follow.

I was not aware of this. It leads me to ask a question.

I am in the habit of keeping 5 gallons of glaze. When the level in the
bucket goes down so much that it is hard to apply through dipping, I
mix more and add it in. Is it the case that I am susceptable to this
problem? I probably go through 5 gallons of my more popular glazes
once a year, but others can take longer.

If you are not having any trouble with your glazes, I wouldn't worry about
it - we have glaze mixes ten years old which are still OK. It probably only
happens with a small number of ingredients - and in my experience only on
low fire glazes.

Cheers

Dave