Tip #7: Making Slips for Decorating
If you haven't decorated with slips, you're missing out. One of the benefits
is that the slips stay put, so designs don't blur or run, unlike many
glazes. This also means you can make textures in the slip that will
stay exactly as you made them. And you can make designs that won't
work with glazes since glazes need multiple coats (ie splattering.)
You can squeeze slip out of a bottle into designs (slip trailing) and use it
for sgraffito (coat with slip then scratch designs in the slip exposing the
raw clay.) (Note: sometimes decorating slips are called engobes,
and the terminology isn't tightly defined; they are generally the same
thing.) Slips are best
applied to leatherhard greenware, but may be used on bisque also.
They may be used on low-fire and high-fire clay. The slip must be
similar to the clay however, so the shrinkage between the two is similar
and the slip doesn't crack or peel off.
Here is a
recipe that is often used because it fits a wide variety of low fire clay
bodies. Thinned, it works well on bisque also.
Kentucky Ball
Clay (Old Mine #4) 40g
EPK (Kaolin,
sometimes called China Clay) 20g
Nepheline
Syenite (flux) 10g
Talc
15g
Silica Sand
(sometimes called Flint) 15g
Here is a
recipe for high fire clay
#6 Tile Clay
(Georgia kaolin) 25g
EPK (Kaolin)
25g
Ball Clay
25g
Frit 3124
15g
Nepheline
Syenite 10g
You can find
many other recipes for slip in books and on the web, including some
specifically for applying to bisque. Mixing:
Note that recipes typically add up to 100g. If you multiply all the
ingredients in the above recipes by 10, you will get 1000 grams, which will
fill about 1/2 of a 5 gallon bucket. You can then
divide this up into 5 1 gallon buckets and mix different stains in each.
As a starting point, use about 15% of the total grams of stain.
(eg 1000 grams / 5 = 200 grams per color, 15% of 200g is 30g, so use 30g of
each stain)
The classic
method is to pre-mix the dry ingredients, then add them to water. But
many experienced potters do not premix their dry ingredients. They
simply drop them into the water and mix with a jiffy mixer or paint mixer
attached to a power drill. Use about half the volume of the dry
ingredients for the amount of water. Mix the ingredients into the
water with your hand or a stick before using the drill, to avoid stirring up
dust. Depending on how well your mixer does, it the slip is lumpy
you will want to push it through a sieve.
The completed slip should be
the thickness of cream for greenware, or slightly thinner on bisque. Apply slip with
a brush, a slip-trailing bottle, or by dipping. As you work, your
piece will dry out, so spritz with water periodically, and wrap
tightly between sessions. You can build up multiple layers of slip to
make very intricate designs.
Note for
purchasing ingredients: 100g is approximately 1/4#. For those who
don't want the convenience of pre-mixed, we also sell engobes in 1 pint
containers, from Western. See the underglaze section of the glaze
page.
copyright 2000, Cindi Anderson, 