Harrington on mon 19 aug 02
Thanks for all the info. Honestly, I don't know how much sulfer my water
clay contains. The technicians at Smooth-On, who manufacture and sell
the rubber for the molds, told me that water clay has sulfer and to
avoid the problem, I should switch to plasticine. I swore I'd rather
die, and slapped on the shellac. Anyone know if there's a clay content
database on the web? And no, I didn't use a mold release over the
shellac. The same guy said only to use the release between the rubber
and plaster. I'll try it next time.
Lisa
Snail Scott wrote:
>
> At 11:07 AM 8/16/02 -0400, you wrote:
> >So I made this torso sculpture out of solid (except for the armature)
> >stoneware clay (cone 6) with the intention of making a mold for bronze
> >casting. To make the mold, I had to coat the wet clay with shellac to
> >prevent the sulfer content of the clay from lousing up the mold rubber.
>
> Your waterbased stoneware clay has that much sulfur
> in it? Are you sure? Many types of plasticine
> (oil-based) clay contain enough sulfur to mess up
> mold rubber, (it's added to improve its handling
> characteristics,) but I never heard of a 'regular'
> clay having anything but trace amounts. Weird!
>
> >After I removed the rubber mold, the clay piece was still intact. Some
> >of the shellac stuck to the rubber...
>
> That shouldn't have happened. Did you use a mold
> release over the shellac?
>
> >So
> >my question is: Is there any reason why I can't hollow this thing out
> >and pop it in the kiln? Would the remaining shellac be a problem, or
> >would it just burn off?
>
> No problem, go right ahead. It'll burn off.
>
> >Also, If I don't intend to glaze the finished piece, should I fire to
> >maturity, or just bisque?
>
> Fire to maturity whenever possible. The piece will
> be stronger, and most bare clays are more attractive
> when fired to vitrification. I've occasionally fired
> pieces only to bisque, when the final surface was a
> non-fired one, but I've always regretted it when it
> came time to ship the damn things.
>
> -Snail
>
> ______________________________________________________________________________
> 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.
Snail Scott on mon 19 aug 02
At 03:17 PM 8/19/02 -0700, you wrote:
>Thanks for all the info. Honestly, I don't know how much sulfer my water
>clay contains. The technicians at Smooth-On, who manufacture and sell
>the rubber for the molds, told me that water clay has sulfer and to
>avoid the problem, I should switch to plasticine.
Really? How weird. I've used Smooth-On products for years, and
never had a problem with any water-based clays. Now, plasticine,
that's another story. If you get a non-sulfur variety (most of
them specify on the label), you'll do just fine, but I've seen
horrible, sticky disasters when an artist failed to tell their
hired mold-maker that they used Roma or one of the other sulfur-
bearing plasticines. Plasticine is handy, but make sure you get
the right stuff! Never a problem with water-based clay, though.
(Many people make their own plasticine using dry clay as the
base; if it had sulfur in it, you'd think they'd have had a
problem, too.) The sulfur in plasticines is added as part of
its manufacturing process, to improve handling characteristics;
it's not naturally present in the other component materials, at
least not in significant percentages.
>I swore I'd rather
>die, and slapped on the shellac...
Don't blame you. Many people loathe the oily feeling plasticine
has. (But, I DO like not having to worry about drying and
shrinkage while working, or while making the mold!) It's a good
idea, when using water-based clays, to use a sealant to eliminate
any porosity (if it's green or fired) and retard drying (if it's
wet), and shellac is as good as any. For myself, if I am making a
rubber mold from ceramic clay, I like to bisque it first, then
make the mold. One exception would be if the piece needs to be
cut into parts to facilitate mold design. In such a case, I might
leave it leather-hard, to allow parts to be cut apart more readily.
(When I worked in a commercial foundry, we nearly always advised
customers who worked in ceramic clay to bring it in bisqued, and
not to plan on firing it later as the mold-making process can be
potentially destructive to the pattern. "You might get it back in
one piece, but don't bet the farm on it..." In many cases, better
to make something with the intention of using it solely as a mold
pattern, than to try to save it for firing later. That's not true
for everything, but it can result in a better, faster (cheaper)
mold if a fragile pattern doesn't have to be saved intact. You
can also make the pattern faster if the requirements for making
a fireable object don't need to be observed, so you're not losing
as much effort if it all 'goes south'.
>And no, I didn't use a mold release over the
>shellac. The same guy said only to use the release between the rubber
>and plaster. I'll try it next time.
Really? In my experience, that rubber sticks permanently to darn
near anything without a release! Smooth-On makes their own
spray-on release (about $8.00 a can) which works well over most
surfaces and is compatible with their product line. (For the
rubber-to-plaster surface, I use plain old Vaseline as a release.)
You probably would have been better off just putting the rubber
over the wet clay, since one of the few things it won't stick to
is wet surfaces.(Did the tech-support guy know you were
shellacking it, or was he thinking of just bare wet clay?)
Still, you shouldn't have any problem hollowing out your solid
clay pattern and firing it. The shellac will burn off just fine.
Good luck!
-Snail
Ceramic Design Group on tue 20 aug 02
Perhaps the state of the art in modeling clay (IMHO) is a product called
Klean Klay
it is available in different consistencies, degrees of hardness
(workability)
and is available from
Art Chemical Products
OI Box 678
Huntington Indiana 46750
(219) 356 2328
We use this material daily in jobs from building models, "claying up"
originals, extruding gutter material for making press dies, etc. etc.
It far outshins any of the other modeling clays I have ever tried.
Jonathan
--
Jonathan Kaplan
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
infor@ceramicdesigngroup.net www.ceramicdesigngroup.net
(use PO BOX for all USPS correspondence)
970 879-9139
Plant Location
1280 13th Street
Steamboat Springs CO 80487
(use PLANT LOCATION for all UPS, Common Carrier, and Courier deliveries)
Harrington on tue 20 aug 02
Yes, I have actually used Klean Klay, and I find it preferable to
plasticine, but somehow it doesn't quite respond to manipulation with
wooden tools the way water clay does. When I was using it, I was only
able to get it in one pound packs, which is a pretty big problem when
you need 50 pounds of clay. I'll consider trying it again if I can get
it in big boxes. After all, water clay can be a hassle too.
Lisa
Ceramic Design Group wrote:
>
> Perhaps the state of the art in modeling clay (IMHO) is a product called
>
> Klean Klay
>
> it is available in different consistencies, degrees of hardness
> (workability)
> and is available from
>
> Art Chemical Products
> OI Box 678
> Huntington Indiana 46750
> (219) 356 2328
>
> We use this material daily in jobs from building models, "claying up"
> originals, extruding gutter material for making press dies, etc. etc.
>
> It far outshins any of the other modeling clays I have ever tried.
>
> Jonathan
>
> --
>
> Jonathan Kaplan
> Ceramic Design Group
> PO Box 775112
> Steamboat Springs CO 80477
> infor@ceramicdesigngroup.net www.ceramicdesigngroup.net
> (use PO BOX for all USPS correspondence)
> 970 879-9139
>
> Plant Location
> 1280 13th Street
> Steamboat Springs CO 80487
> (use PLANT LOCATION for all UPS, Common Carrier, and Courier deliveries)
>
> ______________________________________________________________________________
> 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.
| |
|
