Naomi Rieder on wed 13 oct 99
Two questions about surface prep for terra-sig: I've read Vince Pitlka's
information about terra sig, and have worked with it for some time, but I do
not understand how a "light sanding" on a bone dry surface can eventually
have a smooth surface, without sanding marks. I do get a wonderful glossy
finish, just by rubbing with a chamois, but the sanding marks remain, ever so
slightly. The clay I use is 50/50 KMO4 and talc, no grog. I usually
airbrush, but recently have tried brushing the first few layers on--a very
thin t/s with a specific gravity of about 1.10, sometimes less--and then
airbrushing. The sanding is with 1500 grit pads. Sooo, Vince, or anyone
else who has solved this problem, please, please respond.
Second question: I've read about 2 ceramic artists: Duncan Ross in England,
and Pierre Bayle in France, who work with t/s, but they finish their surface
by smoothing with a rib, and then apply t/s when dry. They don't seem to
have a problem with the t/s popping off, so why would sanding be better?
Much TIA!!!
Naomi Rieder
Cindy Strnad, Earthen Vessels Pottery on thu 14 oct 99
Naomi,
Trying terra sig is still on my "to-do" list, but when I sand things, I use
fine steel wool, which leaves no discernible scratches so far as I can tell.
Would likely be different for applying the more sensitive terra sig, of
course, but maybe better than what you're doing. I'm thinking micro
scratches will help the sig adhere at least as well as larger scratches.
Cindy Strnad
Earthen Vessels Pottery
Custer, SD
Vince Pitelka on thu 21 oct 99
>information about terra sig, and have worked with it for some time, but I do
>not understand how a "light sanding" on a bone dry surface can eventually
>have a smooth surface, without sanding marks. I do get a wonderful glossy
>finish, just by rubbing with a chamois, but the sanding marks remain, ever so
>slightly.
Naomi -
Eliminating the sanding marks depends on the number of coats of terra sig
you apply, and the degree you compress the surface during
polishing/burnishing. The advantage of burnishing is that it levels out the
surface and eliminates all sanding marks, but of course it is extremely
time-consuming. I usually apply ten or twelve thin coats of terra sig
before polishing, and the remaining sanding marks are very minimal.
>The clay I use is 50/50 KMO4 and talc, no grog. I usually
>airbrush, but recently have tried brushing the first few layers on--a very
>thin t/s with a specific gravity of about 1.10, sometimes less--and then
>airbrushing. The sanding is with 1500 grit pads.
I have never used terra sig on a gritless body. All of my experiments with
terra sig over the years have been inspired by the Ancient Clay workshops I
teach, and we always use a gritty claybody in these workshops.
I cannot see any advantage in airbrushing the terra sig, unless you are
masking areas and using the airbrush for specific decorative effects.
Applying smooth flowing coats of thin sig with a brush is quick and
effective. As you apply repeated coats to the bone-dry sanded surface, you
will feel the surface becoming smoother and colder. When it starts to feel
almost "leather hard" (it just feels that way), the accumulated coats should
be thick enough that the residual sanding marks will be minimal.
>Second question: I've read about 2 ceramic artists: Duncan Ross in England,
>and Pierre Bayle in France, who work with t/s, but they finish their surface
>by smoothing with a rib, and then apply t/s when dry. They don't seem to
>have a problem with the t/s popping off, so why would sanding be better?
I don't have an answer for this. I suggest you try to contact them and ask
them. If you do, please let us know what they say. I have had trouble with
sig chipping and flaking when applied to a very smooth surface. And
besides, I do not object at all to a little bit of sanding marks showing.
But each to her/his own. If you do not like the sanding marks, then
obviously you need to do some further experimentation and find out how to
avoid them.
Good luck -
- Vince
Vince Pitelka
Home - vpitelka@DeKalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
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