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Pouring a mold and cleaning greenware are probably the two most important
procedures of ceramics. If a mold is not poured right or to the proper
thickness or the piece is removed from the mold too soon, the final outcome
can be very disappointing. Greenware is very fragile regardless of the
thickness. Pouring a piece too thin will make it even more fragile and
will also increase the chances of the piece cracking in the kiln. I have
always used Excel slip and had great results. There are less expensive
slips around but I think Excel is one of the best. I want my greenware
to be easy to work with so I don't mind paying a little more for the slip.
Most pieces I pour are about 1/4 inch thick, although I pour some larger
pieces thicker so they will be stronger and if I am going to scraffito
or carve on a piece I make sure it is thicker than normal. Some people
will say a piece should be removed from a mold in an hour or two but I
have found that a piece is much easier to handle if it's taken out of the
mold after several hours. I know too much moisture is not good for the
mold but I see no reason to rush and end up deforming a piece because it
was taken out of the mold too soon and is not very firm. There are some
pieces, like lattice plates, that will crack as they shrink if they are
left in the mold too long.
Cleaning greenware is the most boring step in ceramics and it can be
very frustrating. I have cleaned pieces that I wanted to enter in competition
and set them aside for a day. When I have gone back to work on them I see
places I missed the first go round. Someone told me once that you should
clean a piece, set it aside for a day, check it and clean some more and
set it aside for another day, etc. until you don't find any places that
you missed. This may be going to the extreme although if you're working
on a show piece, it's probably not a bad idea. I use an exacto knife and
my fingers to do most of my cleaning. The exacto knife is so much sharper
than a regular cleaning tool and it cleans the seams smoother but I do
have to be careful because it can scratch just as bad as a cleaning tool.
If I have trouble getting the seam as smooth as it should be, I will rub
it gently with my thumb until it's smooth. I use as little water as possible
on my greenware and I use a cleaning pad as little as possible to avoid
unnecessary scratches. If there is a seam in the middle of a design, a
scraffito tool can be used to reshape the part of the design that is destroyed
during cleaning.
One of the products I enjoy working with most is Duncan's Cover Coat
Underglazes. They are nice and creamy and brush on greenware better than
some other underglazes. I normally brush on underglazes, although sponging
them gives a nice slightly textured affect. Underglazes are normally fired
at the same temperature as greenware. Textured glazes that go on greenware
seem to come out brighter and colors if I fire them to cone 02.