Url Krueger on mon 13 dec 04
I don't have a lot of experience dipping as a glaze application method
so a whole kiln load of pots came out with too thin a layer of glaze,
especially on the outside of the pots.
Glaze slop had a density of 1.4 g/ml,
Bisque was to ^04, and
I submerged whole pot for 4 seconds.
Dipping half the pot a second time for 4 seconds came out about right.
As I understand it to get a thicker layer I can:
Increase the density of the glaze, or
Lower the bisque cone, or
Dip for longer.
Based on your experience which method would you try first?
Thanks...
Earl...
Cindy on tue 14 dec 04
Dear Earl,
First, I would not try to measure the sg of the glaze. If I try twice in a
row on the same glaze, I tend to get different measurements. Maybe it's my
technique, but for me, this *always* doesn't work. If you really want
precision you can measure, get some sort of device for measuring the
thickness of the actual glaze coat on the pot. That will tell you much more.
After a while, you get a feel for how thick a given glaze should be just by
looking at it and stirring it in the bucket. One way to help this along is
to try scratching the just-dried glaze coat and see how thick it is.
Naturally, the criteria will vary from glaze to glaze, but a general rule of
thumb is that it should be about the thickness of a credit card. Also, if
your pot looks a little bumpy after glazing, or you can see any clay through
the glaze at all, the glaze is too thin.
You must remember that thinly thrown or constructed pots will not take on as
much glaze in a given time as a thicker-walled piece will do. Adjust your
submersion time or number of dips accordingly. You do have to experiment.
Unfortunately, nobody gets to learn this the easy way. Even with a mentor
standing over your shoulder, you'll still eventually have to do it the hard
way. Bummer!
Oh yes, and I forgot to mention--in case you haven't noticed, warm pots
absorb a lot more glaze than if they've cooled completely. And if the room
is cold, you'll need thicker glaze. You may adapt to the weather, but your
pottery materials won't.
Sometimes, a pot will be so thin, or a glaze so over-watered, that dipping
it for one long time isn't going to work. The reason being, the glaze will
drip and slump--just like paint that has been applied too thickly in the
first coat. When the glaze or the pot is this thin, you have to wait until
the pot is sufficiently dry (which may take longer than a count of 10, or
whatever you usually do) before you try to give it a second coat. In future,
you might want to dip the thin pots first, then add a little more water to
the glaze.
My usual routine for stirring glazes is like this: I dip off quite a lot of
the water sitting on top. (I save it, in case it makes any difference--with
some glazes it can.) Stir the glaze up really well with an electric drill
and (plastic) paint stirrer. (Reason for the plastic--it doesn't shave bits
off the inside of the bucket.) I am definitely going to try Russell's
suggestion of using a toilet brush first, BTW. Once stirred, I add back
water until the glaze looks right--generally about the consistency of medium
to heavy cream.
I dip small pots first--cups, little bowls, votive candle holders--anything
that will be really thin. I add back more water, then dip medium pots. If I
have any really large pots to do, I add back still more water. You need the
most water if you're going to have to pour the glaze over the pot. For some
reason, that seems to make the pots grab more glaze.
So, that's the routine. Hope you have a shorter learning curve than I have
had so far. ;)
Merry Christmas,
Cindy in SD
Subject: Glaze layer too thin
> I don't have a lot of experience dipping as a glaze application method
> so a whole kiln load of pots came out with too thin a layer of glaze,
> especially on the outside of the pots.
>
> Glaze slop had a density of 1.4 g/ml,
> Bisque was to ^04, and
> I submerged whole pot for 4 seconds.
> Dipping half the pot a second time for 4 seconds came out about right.
>
> As I understand it to get a thicker layer I can:
> Increase the density of the glaze, or
> Lower the bisque cone, or
> Dip for longer.
>
> Based on your experience which method would you try first?
>
> Thanks...
>
> Earl...
>
>
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Ron Roy on wed 15 dec 04
Hi Earl,
I always adjust the glaze slop for thicker or thiner - and use a piece of
bisque - and scratch through the glaze as soon as it is dry enough - to see
how thick it is.
Make two tiles and glaze with different thicknesses - scratch through one
and fire the other - you then know what thickness gives what result.
This method is fool proof as it takes into account different absorbency and
thickness in the bisque and changes in the reology of the glaze slop.
RR
>I don't have a lot of experience dipping as a glaze application method
>so a whole kiln load of pots came out with too thin a layer of glaze,
>especially on the outside of the pots.
>
>Glaze slop had a density of 1.4 g/ml,
>Bisque was to ^04, and
>I submerged whole pot for 4 seconds.
>Dipping half the pot a second time for 4 seconds came out about right.
>
>As I understand it to get a thicker layer I can:
> Increase the density of the glaze, or
> Lower the bisque cone, or
> Dip for longer.
>
>Based on your experience which method would you try first?
>
>Thanks...
>
>Earl...
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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