Kate Johnson on thu 20 jan 05
Hello, all...would #6464 Zirconium yellow Mason stain affect how an object
accepted a transparent gloss glaze? Has anyone had experience with this?
It's the only thing I can pin down a problem on a couple of my slip
decorated pieces to--that's what appears to be in common.
One piece has been reglazed twice now, and the surface is still mottled and
matte in places--it's in for the third time, after which I'll give up!
Another out of the kiln the other day was marbled with this slip, as well as
white and one made with manganese and cobalt...where the yellow was, I now
have matte marbling, not glossy.
Very strange, as I haven't had this problem before...
Thanks!
Best--
Kate
Paul Lewing on thu 20 jan 05
on 1/20/05 10:45 AM, Kate Johnson at graphicart@EPSI.NET wrote:
> Another out of the kiln the other day was marbled with this slip, as well as
> white and one made with manganese and cobalt...where the yellow was, I now
> have matte marbling, not glossy.
Kate, the problem may be the incredibly fine particle size of the stain.
This sometimes blocks the pores in bisqueware and prevents proper adhesion
of the raw glaze coating. If there's a high percentage of stain in the
slip, which there probably is if it's a strong color, that may be what's
happening. So it wouldn't be so much that it's this stain, but that it's a
stain at all, rather than a raw oxide like the manganese and cobalt. Have
you used this slip with other stains?
It may also be just this stain. Zirconium is one of the most refractory
things around, and this yellow one also has silica in it. That could be
causing the mattness.
Can you use less stain? Or can you increase the particle size of some other
ingredient in your slip? Maybe a different clay or a coarser silica, if it
has either of those? That might help with the porosity thing.
Paul Lewing, Seattle
Kate Johnson on thu 20 jan 05
Hi Paul, and thank you for responding...
>> Another out of the kiln the other day was marbled with this slip, as well
>> as
>> white and one made with manganese and cobalt...where the yellow was, I
>> now
>> have matte marbling, not glossy.
> Kate, the problem may be the incredibly fine particle size of the stain.
> This sometimes blocks the pores in bisqueware and prevents proper adhesion
> of the raw glaze coating.
One of these was raw glazed, and the other wasn't, IIRC...
If there's a high percentage of stain in the
> slip, which there probably is if it's a strong color, that may be what's
> happening.
Yes, I was trying for a good strong yellow. Ooops.
So it wouldn't be so much that it's this stain, but that it's a
> stain at all, rather than a raw oxide like the manganese and cobalt. Have
> you used this slip with other stains?
No, I guess I haven't, just with oxides.
> It may also be just this stain. Zirconium is one of the most refractory
> things around, and this yellow one also has silica in it. That could be
> causing the mattness.
> Can you use less stain?
I don't believe I'll be wanting to use that one at ALL any more. I was
attempting another way of getting that honey-color on the finished product,
since my RIO in transparent glaze is still only producing a rather light
yellow. I thought maybe if I started out with a yellow, then glazed with
the RIO mixture, I might come closer to the 18th C. effect I'm after. Not
if it's matte, though!
Or can you increase the particle size of some other
> ingredient in your slip? Maybe a different clay or a coarser silica, if
> it
> has either of those? That might help with the porosity thing.
It's only a liquid version of my white earthenware clay--I make it myself,
seived 3-4 times. No idea if it has silica in it or if it's just clay, but
I suspect the latter.
Thank you! I'm glad my hypothesis sounds correct...just sorry I used it on
the owl and owlets sgraffito plate that I worked myself silly on.
Best--
Kate
Snail Scott on sat 22 jan 05
At 07:41 PM 1/20/2005 -0600, Kate J. wrote:
>...just sorry I used it on
>the owl and owlets sgraffito plate that I worked myself silly on...
I'm only skimming Clayart right now since
the spring semester has begun, but I noticed
your post.
NEVER USE YOUR WORK IN PLACE OF A TEST TILE!
When Tony and other folks talk about testing on
actual pieces, they are talking about simple
thrown production ware - dozens per hour. They
might as well sacrifice a few to glaze testing.
That doesn't mean that you should treat more
time-consuming pieces that way. If it takes you
more than an hour to make, don't use it for a
test piece.
Now that you've got your designs and slipware
working well, keep at them, but DON'T use them
for glaze tests! Make simple little things
for that. If you don't want to do useless
test samples, maybe just make coaster-sized
plates with a tiny bit of slip trailing. You'll
have to move up to the 'real' work eventually,
since they'll always act a little bit differently
from smaller test pieces, but don't start out
that way.
Let the plates accumulate as bisque while you
refine your glazes. Get them into the right
ballpark, THEN glaze the work!
-Snail
Kate Johnson on mon 24 jan 05
Hi Snail!
> At 07:41 PM 1/20/2005 -0600, Kate J. wrote:
>>...just sorry I used it on
>>the owl and owlets sgraffito plate that I worked myself silly on...
>
>
> I'm only skimming Clayart right now since
> the spring semester has begun,
Busy here too, or I would have answered sooner!
but I noticed
> your post.
>
> NEVER USE YOUR WORK IN PLACE OF A TEST TILE!
Yes, ma'am.
> When Tony and other folks talk about testing on
> actual pieces, they are talking about simple
> thrown production ware - dozens per hour.
DEFINITELY not what I do. I've been shaking my head at the mugs
discussion...I can make about 4-6 a DAY, the way I work...I'm definitely not
going to get rich any time soon.... (And no, not talking about a full 8
hour day doing one thing...I can't keep up that pace, and have to trade
off...)
They
> might as well sacrifice a few to glaze testing.
> That doesn't mean that you should treat more
> time-consuming pieces that way. If it takes you
> more than an hour to make, don't use it for a
> test piece.
Yes, ma'am. Truthfully, honesty, please don't beat me--I didn't. I don't
know if you noticed the little sgraffito sparrow-like bird tile on my Yahoo
album...that WAS the test. It looked great...golden yellowish, shiny but
not TOO shiny, somewhere in the neighborhoos of satin rather than high
gloss. Perfect, I thought...so I went for it with the owl plates.
>
> Now that you've got your designs and slipware
> working well, keep at them, but DON'T use them
> for glaze tests! Make simple little things
> for that. If you don't want to do useless
> test samples, maybe just make coaster-sized
> plates with a tiny bit of slip trailing. You'll
> have to move up to the 'real' work eventually,
> since they'll always act a little bit differently
> from smaller test pieces, but don't start out
> that way.
Didn't.... Though I'll admit I did only the one test tile, I just didn't
expect it to react THAT differently! And yes, very frustrating--both those
owl plates had several hours in them. Different location in the kiln? Slip
mixture older or more concentrated with age? Dunno.
>
> Let the plates accumulate as bisque while you
> refine your glazes. Get them into the right
> ballpark, THEN glaze the work!
Back to the drawing board...
Best--
Kate
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