ronroy@CA.INTER.NET on sat 21 apr 12
Hi John,
Often the cause is can be traced to the MOR (modulus of rupture) of
the clay in the recipe - EPK has a rather low MOR compared to ball
clays. Clays with higher MOR's are stronger as they dry - sometimes
adding bentonite to the glaze will help.
In this case ball clay should work - what ball clays do you have? I'll
reformulate if you want.
RR
Quoting "POST, JOHN" :
> I had a glaze I used in the past that had 5% titanium dioxide in it
> and it would often crawl. I cut that back to 3.5% and eliminated
> the problem. 10% titanium sounds like it might be the source of
> your problem. I would try cutting that back some and see if the
> crawling stops without changing the visual appearance of the glaze
> too much.
>
>
> --------------------------------
> Subject: Cure for crawling
>
> I can almost get this glaze to apply
> thick enough to give me the result I want. When I get it thick enough
> I get checking as it dries, then a crawl pattern from the
> fire.
>
>
> the glaze
> g358 c8 ox slate slow cool cycle
>
> Minspar 200 27.8
> Whiting 23.3
> Volcanic Ash 21.4
> EPK 12.6
> Flint 12.4
> Zinc ox 2.4
>
> Add 10% titanium ox and 4% copper carb.
>
Larry Miller on sat 21 apr 12
I'm glazing fireplace tiles with a semimat charcoal/green glaze and
firing to c8 electric.=3DA0 I can almost get this glaze to apply
thick enough to give me the result I want. When I get it thick enough
I get checking as it dries, then a crawl pattern from the
fire.
I have tried deflocing with a bit of sodium silicate, I think it
helped a bit. Also replaced some and then all of the epk with
calcined
epk and then defloced with sodium silicate. (it visibly changed the
slurry, whats up wid that?)
the glaze
g358 c8 ox slate slow cool cycle
Minspar 200 27.8
Whiting 23.3
Volcanic Ash 21.4
EPK 12.6
Flint 12.4
Zinc ox 2.4
Add 10% titanium ox and 4% copper carb.
Calcine some of the vocanic ash? literature says too fine particle
size in glaze is a possibility.
I'd like to just dip these tiles, it works fine when I get the
thickness. I'm trying a second coat by spraying today to see if
I can get the thickness up a bit.
I can get acceptable results with some wasters, but why can't I get it
on thick? Inquiring minds want to know.
Larry near Alden, Mich
POST, JOHN on sat 21 apr 12
I had a glaze I used in the past that had 5% titanium dioxide in it and =3D
it would often crawl. I cut that back to 3.5% and eliminated the =3D
problem. 10% titanium sounds like it might be the source of your =3D
problem. I would try cutting that back some and see if the crawling =3D
stops without changing the visual appearance of the glaze too much.
--------------------------------
Subject: Cure for crawling
=3D20
I can almost get this glaze to apply
thick enough to give me the result I want. When I get it thick enough
I get checking as it dries, then a crawl pattern from the
fire.
the glaze
g358 c8 ox slate slow cool cycle
Minspar 200 27.8
Whiting 23.3
Volcanic Ash 21.4
EPK 12.6
Flint 12.4
Zinc ox 2.4
Add 10% titanium ox and 4% copper carb.
Edouard Bastarache on sat 21 apr 12
Crawling is caused by a high index of surface tension in the melting glaze.
It is triggered by adhesion problems, often caused by bad application. It
occurs where a glaze is excessively powdery, and does not fully adhere to
the surface of the clay. This can be alleviated by the addition of a small
amount of gum to the glaze batch. Crawling is more common in matt glazes
than in fluid ones; sometimes the problem of crawling can be adjusted by th=
e
addition of a small amount of extra flux. Crawling can also occur when one
glaze is applied over another, particularly if the first is allowed to dry
out completely before the second application. Some fluxes, particularly zin=
c
and magnesium, are likely to cause crawling when used in excess. Calcining
part of the zinc can help this problem (Robin Hopper in The Ceramic
Spectrum)
Plejkore,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://smart2000.pagesperso-orange.fr/bloggs_edouard.htm
http://www.facebook.com/edouard.bastarache
----- Original Message -----
From: "Larry Miller"
To:
Sent: Saturday, April 21, 2012 9:39 AM
Subject: Cure for crawling
I'm glazing fireplace tiles with a semimat charcoal/green glaze and
firing to c8 electric. I can almost get this glaze to apply
thick enough to give me the result I want. When I get it thick enough
I get checking as it dries, then a crawl pattern from the
fire.
I have tried deflocing with a bit of sodium silicate, I think it
helped a bit. Also replaced some and then all of the epk with
calcined
epk and then defloced with sodium silicate. (it visibly changed the
slurry, whats up wid that?)
the glaze
g358 c8 ox slate slow cool cycle
Minspar 200 27.8
Whiting 23.3
Volcanic Ash 21.4
EPK 12.6
Flint 12.4
Zinc ox 2.4
Add 10% titanium ox and 4% copper carb.
Calcine some of the vocanic ash? literature says too fine particle
size in glaze is a possibility.
I'd like to just dip these tiles, it works fine when I get the
thickness. I'm trying a second coat by spraying today to see if
I can get the thickness up a bit.
I can get acceptable results with some wasters, but why can't I get it
on thick? Inquiring minds want to know.
Larry near Alden, Mich
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