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 rawclay.) (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 onbisque 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 twoissimilar and the slipdoesn'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.

  1. Kentucky Ball Clay (Old Mine #4) 40g
  2. EPK (Kaolin, sometimes called China Clay) 20g
  3. Nepheline Syenite (flux) 10g
  4. Talc 15g
  5. Silica Sand (sometimes called Flint) 15g

Here is a recipe for high fire clay

  1. #6 Tile Clay (Georgia kaolin) 25g
  2. EPK (Kaolin) 25g
  3. Ball Clay 25g
  4. Frit 3124 15g
  5. 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 youmultiply all the ingredients in the above recipes by 10, you will get 1000 grams, whichwill fill about1/2 of a 5 gallon bucket.You can then divide this up into 5 1 gallon buckets and mix different stains in each. Asa starting point, use about 15% of the total gramsof 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 apower 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 howwell 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 willdry out, so spritz with waterperiodically, 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 engobesin 1 pint containers, from Western. 

Check out our selection of underglaze.

copyright 2000, Cindi Anderson, www.bigceramicstore.com
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