Lou Roess on fri 26 nov 04
Is there some rule of thumb about the consistency of glazes for
different application methods? For instance is a glaze for pouring
generally thicker than one for dipping? How about brushing and
spraying? I'm not asking for specific gravities, just for the relative
thicknesses
Thanks,
Lou in Colorado generally a lurker but having a lot of questions
lately..
william schran on sat 27 nov 04
Lou in Colorado wrote:>Is there some rule of thumb about the
consistency of glazes for
different application methods? For instance is a glaze for pouring
generally thicker than one for dipping? How about brushing and
spraying? <
From thinnest to thickest: spraying, dipping & pouring (same), brushing.
For all methods of glaze application, one can vary thickness by
glazing dry bisque, dampening or wetting the pot.
Bill
Cindy on sun 28 nov 04
Hello, Lou
Consistency of dipping and pouring glazes varies between whole milk and
heavy cream. What you need depends on the temperature of your wares (warm
will absorb more moisture and therefore attract a thicker glaze coat), the
thickness of the wares (thicker walls absorb more moisture, etc.), the
temperature to which you have bisqued the wares (lower bisque means more
absorbent wares) and the behavior of the individual glaze (runny glazes need
a thinner coat . . . some glazes look better with a thicker coat, and so
on).
Glazes for painting need to be smoother and have more flow. Sometimes it
helps to add CMC and non-toxic antifreeze or other additives of your choice.
I generally like paint-on glazes to be a little bit thicker than pouring and
dipping glazes, but I don't do a lot of brush work, so I'm no expert on
paintable glazes.
For spraying, you need a thinner glaze with non-toxic antifreeze added (just
a small amount--maybe a half tsp. to a half-pint jar--I just pour a little
bit in. For spraying, you should also sieve the glaze. It's a hassle, but it
saves frustration later.
Hope this helps,
Cindy in SD
John Rodgers on mon 29 nov 04
Glazes vary quite a bit in their reaction to application as thick or
thin. Also the glazing method used has some bearing as to whether the
application is thick or thin. I personally use a thinner mix fr
spraying, a thicker mix for dipping and brushing. I find that prefer to
know the numbers on each glaze for each application as well. That is,
after experimentation, I like to know what the specific gravity or
density of a particular glaze is for a particular application. I like to
use SpG of 1.3 for dipping Floating Blue. When I spray it I reduce the
SpG to 1.0 and then apply 10 coats. I really like the effect. I try and
work out the numbers on all my glazes. Gives better control.
Regards,
John Rodgers
Chelsea, AL
Lou Roess wrote:
> Is there some rule of thumb about the consistency of glazes for
> different application methods? For instance is a glaze for pouring
> generally thicker than one for dipping? How about brushing and
> spraying? I'm not asking for specific gravities, just for the relative
> thicknesses
> Thanks,
> Lou in Colorado generally a lurker but having a lot of questions
> lately..
>
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Christy Pines on mon 29 nov 04
So in trying to make glazes the right consistency for the application
technique, do you keep two separate batches of glaze, as in your example of
Floating Blue below? Or do you keep one batch at 1.3 and then thin a portion
of it to 1.0 when you want to spray? Do you have a formula that you use to
go from 1.3 to 1.0 or did you measure how much water it took the first time
and that's the measurement you use consistently ever since?
I'm most curious about the practical side of having one glaze at two
different specific gravity measurements and how that works in the studio. I
am working on my preferred specific gravity for dipping the glazes I use
right now, having seen the dramatic differences the thickness can make over
the last 4 days of back to back glaze firing.
Thanks in advance for your input.
christy in connecticut
cpines at ix.netcom.com
----- Original Message -----
From: "John Rodgers"
> after experimentation, I like to know what the specific gravity or
> density of a particular glaze is for a particular application. I like to
> use SpG of 1.3 for dipping Floating Blue. When I spray it I reduce the
> SpG to 1.0 and then apply 10 coats. I really like the effect. I try and
> work out the numbers on all my glazes. Gives better control.
>
Cindy on tue 30 nov 04
Hi, Christy
I'm not the writer of the post you were asking about, buy maybe I can help.
You don't need to keep two batches of glaze. You would need to adjust the sg
before using it again in any case because your pots don't take up equal
quantities of glaze material and water when you dip them.
I've never been able to make the sg tester work consistently in thick glaze,
even though I bought one especially for that purpose. But maybe you'll have
better luck. I believe altitude and barometric pressure have some effect on
your readings as well. I'm sure it would make things easier for you if you
purchase a graduated cylinder to use for testing. You can probably get one
from www.sciplus.com . That's American Science and Surplus.
What you do is ladle off some water before you mix up the glaze. Save
it--you may end up adding it back in. Mix thoroughly and then test
immediately. Add back in water as necessary. After a while you get a feel
for how much water you want to see sitting on top of a given glaze before
you mix it up.
For spraying, you just take out some well-mixed glaze, add some water,
sieve, add propylene glycol--maybe a tsp. or so (that's non-toxic antifreeze
. . . the kind you buy for your RV) and pour it into your sprayer jar. Oh
yes--test the sg first. The propylene glycol improves the flow and keeps the
glaze moist just a bit longer on the pot. When you're done, you can save it
or pour it back into the glaze bucket.
Good luck,
Cindy in SD
Lee Love on tue 30 nov 04
Christy Pines wrote:
>So in trying to make glazes the right consistency for the application
>technique, do you keep two separate batches of glaze, as in your example of
>Floating Blue below? Or do you keep one batch at 1.3 and then thin a portion
>of it to 1.0 when you want to spray? Do you have a formula that you use to
>go from 1.3 to 1.0 or did you measure how much water it took the first time
>and that's the measurement you use consistently ever since?
>
Christy,
Glaze thickness is critical for the application of my
teacher's nami jiro glaze. Too thick and it was too opaque to allow
the inlay to show. Too think and the iron body made the glaze too
dark. We would change the thickness of the glaze at least a half dozen
times during glazing. Glaze thickness was judged by scratching the
surface and looking at the actual thickness of application, first of a
test shard and then on an actual pot. Specific gravity was not
accurate enough for my teacher's tolerances because barometric pressure,
humidity, thickness of the bisque and the hardness of the bisque are all
values that make S.G. inaccurate.
I follow a similar procedure: When you first start
glazing, you remove the water off the top of the glaze bucket. Then
you mix and add a small amount of water before your first test. The
initial thickness, before the surface scratch test, is judged by how
the glaze pours out of the ladle. The thickness glaze is used to
glaze the thinnest pots. Pots are glazed from thinnest to thickest.
When the thinnest pots are finished, more water is added and then the
next thickest pots are glaze. This continues until the largest pots
are glazed and the most water is added to the glaze.
If too much water is accidently added, a small bucket of very
thick glaze is kept on hand and is added to thicken up the glaze thickness.
This isn't the end of it either, because a different amount
of kaolin is in the same glaze according to where it is going to be put
in the kiln, from 25% in the hottest part of the noborigama to 5% in the
coolest part of the kiln.
So, if you multiply a minimum of 5 thickness of application
with the minimum of 3 different levels of kaolin added, you end up
with 15 different versions of the same glaze: all different thickness
and temps that allow different thickeness of ware in different parts of
the kiln look exactly the same.
If you are using this method with a Minnesota type shino
glaze that has soda ash in it, you save the water you scoop off of the
glaze in the beginning, to add to the glaze when thicker work is glaze.
The other aspect that helps in the uniformity of glaze
thickness is the sponging of the bisque with a wet sponge before it is
glaze.
--
in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
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mailtoandrew@FSMAIL.NET on tue 30 nov 04
Hi,
Isnt a glaze with an SG of 1.0 just water?
Regards,
Andrew
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