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Re: Sgraffito: how to?

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From: Marvin Bartel (marvinpb_at_TeacherArtExchange)
Date: Tue Oct 05 2004 - 09:48:00 PDT


I often use several colored slips that are put on the pot while clay
is soft or no harder than leatherhard (for satisfactory slip
adhesion). To encourage students to think artistically, I assign
them to to use at least three different size sharpened stick points
for line variation when scratching their designs, patterns, motifs,
etc on the clay. No pin point tools are allowed on their first
efforts because the glazing hides it too much when the lines are too
thin. I encourage bold, simple, and fairly quick approaches until
they see some finished results.

In my work, my favorite drawing tool is a quarter inch diameter wood
dowel rod, not pointed, but left with a square cut end. When I draw
with the corner of the square cut end, it gives line thickness
variation adding movement and life to the lines. I only work on wet
clay to avoid dust. I leave the burrs around the scratches. Before
glazing, I rub the burrs off of the bisque with a small piece of
broken kiln shelf or a hard piece of broken brick. Bisque dust is
not so fine and is much less apt to get airborne and hazardous to
breath.

I show no examples, but I have students practice on clay scrap before
doing it on the projects. For ideas, they make sketches and make
lists about themselves. We study cultures as a follow up after they
have fired some work. Our work is to express our selves and our
culture just as their work expresses themselves their culture.

Simple slip recipes I use
Since slip does not melt, you do not need to be accurate for slip as
you would for glaze recipes - use any convenient measuring device.

Brown
1 scoop of red iron oxide
3 scoops of the same clay used for the pots (dry scrap is okay)
Put it in water. Let it set quietly until the clay is mushy. Stir
until thick as coffee cream.

Blue
1 spoon cobalt carbonate or oxide
9 spoon of dry clay
I add some liquid blue tempera to make it look blue when using - just
guess at this.
(Cobalt is toxic if you breath it repeatedly, but it is not too bad to touch)

Copper (green in electric kiln)
1 spoon copper carbonate
6 spoons dry clay

As you notice, some coloring metals are much stronger than others.
These can be combined in any way you want to get other colors.
Adding rutile is like adding some yellowish color.

I tell students that thick coats (several applications) of slip will
look different than thin coats. They should be sure to try both
approaches to see what they like better. Sometime thin coats
disappear entirely under glazes. Some glazes cover more than others.
Thick glazes cover more than thin glazes. By not showing an example
first, they have no reason to expect a certain effect, and I tell
them to expect surprises. It never fires the way you expect it to
the first time. Their friends will always like it better than they
do because friends do not pre-visualize the result before it if fired.

This is an example of a piece with brown slip and a light tone glaze
over it. The slip was combed with an old credit card I notched with
a scissors. I never buy a tool if I can make it. I often use things
they were not intended to be used for.
http://www.goshen.edu/~marvinpb/ex22.htm

VARIATION using wax

Paint a slip design on the leatherhard or softer piece.
When the slip firms to leatherhard, cover the area with wax resist
(available from ceramic suppliers - it is wax emulsified in water).
When the wax dries, at leatherhard stage scratch additional lines,
hatching, etc.
Paint with a different colored slip. Give it several slip coats.
Slip that is on top of the wax will rub off after firing before
glazing.

Marvin Bartel
bartelart.com

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