Randy McCall on wed 26 oct 05
Would someone explain the use of veegum C in glazes and the amounts to use.
I have looked at the archives and I don't see anything that specifically
addresses the above two issues.
It may be there but I can't find it.
Randy
Pottery Web Site
members.tripod.com/~McCallJ/index.html
South Carolina
David Beumee on thu 27 oct 05
Would someone explain the use of veegum C in glazes and the amounts to use.
I haven't had much luck with the use of Veegum Cer in glazes because of its deflocculating effect. For a celadon or other type of glaze where addition of bentonite is detrimental because of high iron content, and/or where the base glaze contains little or no clay, 2% Veegum T works well for the addition of a clay-like material that helps float the glaze and adds no iron content. I like to mix all ingredients dry inside a bag before adding to water.
David Beumee
Lafayette, CO
-------------- Original message ----------------------
From: Randy McCall
> Would someone explain the use of veegum C in glazes and the amounts to use.
> I have looked at the archives and I don't see anything that specifically
> addresses the above two issues.
>
> It may be there but I can't find it.
>
>
> Randy
>
> Pottery Web Site
> members.tripod.com/~McCallJ/index.html
> South Carolina
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Paulette Carr on mon 31 oct 05
Randy,
Veegum is a thixotrope which behaves in a suspension such as glazes
and slips like bentonite. Veegum Cer (Veegum C) is a mixture of
Veegum and CMC. The benefit of this material is that it keeps glazes
in suspension, and binds and hardens the surface of the glaze so that
it can be handled after drying.
I do not observe the deflocculation effect that David mentioned. We
may be using very different glazes. All of my glazes are thickish
and well "floated." There are differences between glazes, however,
due mainly to the type of fluxes (sodium vs potassium), and other
ions present. Generally I can adjust the thickness and viscosity
(flow) of the glaze to what I want using Darvan 7 to thin
(deflocculant), or a saturated Epsom salt solution (magnesium sulfate
- flocculant) to thicken.
The trick with VgC is that the glaze may apply thinner on the pot
than you are used to for what appears to be a glaze of similar
"creaminess"/thickness/viscosity. You can adjust for this by using
less water than you normally use in the glaze preparation, and then
thinning the glaze with something like Darvan 7 - it makes the glaze
wetter with more glaze materials in suspension, but be careful,
because if you use too much, it can cause the glaze to gel. It is
confusing, I know, but this is over-deflocculation. In all cases, it
is a good idea to scratch the surface to determine the real
thickness. If you know the specific gravity of the glazes which you
have been successfully using, you can prepare your glazes containing
VgC to the same specific gravity, and then adjust for viscosity/flow.
All this said, I prepare my glazes for brushing, rather than dipping,
so I aim for a paint-like, slightly deflocculated glaze. When trying
a new glaze, I start with 1.5% VgC based on the dry weight of the
glaze. If I already have materials in the glaze that are
thixotropes like Gerstely Borate, or a glaze with a high clay
content, I may drop this to 1%, or even less, if I am preparing a
pouring glaze. I, almost always, substitute the VgC for bentonite.
If you are dipping or pouring, you may want to lower the %-age amount
of VgC. Zamek's book lists fro 1/8% - 1.5% VgC. It is always true
that you have to try it, even if you are provided with guidelines.
As for spraying - I do not know, but Jonathan Kaplan (whom I believe,
is currently off-list and unavailable) has some very valuable posts
in the archives (April, 2005 - Spraying glazes and glaze rheology) -
just follow that thread.
For basic preparation, I weigh out all the ingredients, including VgC
and pour them into a smallish amount of hot water, and allow them to
slake for several hours or overnight. I then sieve the glaze twice:
once through 50 mesh (60 will do), and finally through 80 mesh. The
slaking throughly wets the ingredients, and the sieving mixes and
suspends all ingredients without the necessity to use high shear
mixing. Here, I record or adjust the specific gravity to make
certain that I know how much solid is suspended in the water. Then I
can adjust the flow and recheck the specific gravity. It sounds like
it takes a lot longer than it actually does.
I hope that this helps, and if you have any further questions, let me
know. Best of luck with your glazes!
Regards,
Paulette Carr
Paulette Carr Studio
Member/Potters Council
St. Louis, MO
Randy McCall wrote:
Would someone explain the use of veegum C in glazes and the amounts
to use. I have looked at the archives and I don't see anything that
specifically addresses the above two issues.
Randy McCall on mon 31 oct 05
Paulette thanks for the information and instructions. Those are the best
descriptions with amounts I have been able to find.
Randy
Pottery Web Site
members.tripod.com/~McCallJ/index.html
South Carolina
----- Original Message -----
From: "Paulette Carr"
To:
Sent: Monday, October 31, 2005 1:41 AM
Subject: Veegum C????
> Randy,
>
> Veegum is a thixotrope which behaves in a suspension such as glazes
> and slips like bentonite. Veegum Cer (Veegum C) is a mixture of
> Veegum and CMC. The benefit of this material is that it keeps glazes
> in suspension, and binds and hardens the surface of the glaze so that
> it can be handled after drying.
>
> I do not observe the deflocculation effect that David mentioned. We
> may be using very different glazes. All of my glazes are thickish
> and well "floated." There are differences between glazes, however,
> due mainly to the type of fluxes (sodium vs potassium), and other
> ions present. Generally I can adjust the thickness and viscosity
> (flow) of the glaze to what I want using Darvan 7 to thin
> (deflocculant), or a saturated Epsom salt solution (magnesium sulfate
> - flocculant) to thicken.
>
> The trick with VgC is that the glaze may apply thinner on the pot
> than you are used to for what appears to be a glaze of similar
> "creaminess"/thickness/viscosity. You can adjust for this by using
> less water than you normally use in the glaze preparation, and then
> thinning the glaze with something like Darvan 7 - it makes the glaze
> wetter with more glaze materials in suspension, but be careful,
> because if you use too much, it can cause the glaze to gel. It is
> confusing, I know, but this is over-deflocculation. In all cases, it
> is a good idea to scratch the surface to determine the real
> thickness. If you know the specific gravity of the glazes which you
> have been successfully using, you can prepare your glazes containing
> VgC to the same specific gravity, and then adjust for viscosity/flow.
>
> All this said, I prepare my glazes for brushing, rather than dipping,
> so I aim for a paint-like, slightly deflocculated glaze. When trying
> a new glaze, I start with 1.5% VgC based on the dry weight of the
> glaze. If I already have materials in the glaze that are
> thixotropes like Gerstely Borate, or a glaze with a high clay
> content, I may drop this to 1%, or even less, if I am preparing a
> pouring glaze. I, almost always, substitute the VgC for bentonite.
> If you are dipping or pouring, you may want to lower the %-age amount
> of VgC. Zamek's book lists fro 1/8% - 1.5% VgC. It is always true
> that you have to try it, even if you are provided with guidelines.
> As for spraying - I do not know, but Jonathan Kaplan (whom I believe,
> is currently off-list and unavailable) has some very valuable posts
> in the archives (April, 2005 - Spraying glazes and glaze rheology) -
> just follow that thread.
>
> For basic preparation, I weigh out all the ingredients, including VgC
> and pour them into a smallish amount of hot water, and allow them to
> slake for several hours or overnight. I then sieve the glaze twice:
> once through 50 mesh (60 will do), and finally through 80 mesh. The
> slaking throughly wets the ingredients, and the sieving mixes and
> suspends all ingredients without the necessity to use high shear
> mixing. Here, I record or adjust the specific gravity to make
> certain that I know how much solid is suspended in the water. Then I
> can adjust the flow and recheck the specific gravity. It sounds like
> it takes a lot longer than it actually does.
>
> I hope that this helps, and if you have any further questions, let me
> know. Best of luck with your glazes!
>
> Regards,
> Paulette Carr
> Paulette Carr Studio
> Member/Potters Council
> St. Louis, MO
>
>
> Randy McCall wrote:
> Would someone explain the use of veegum C in glazes and the amounts
> to use. I have looked at the archives and I don't see anything that
> specifically addresses the above two issues.
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
| |
|
