Slipware

Starting around 10,000 years ago, potters of the Neolithic era harvested clays of different colors and painted water-thinned mixtures on pottery as surface decoration.  Examples of slip painting date back as early as 8000 BC in Egypt, Anatolia, and other Mediterranean and Middle Eastern locations.  In predynastic Egyptian pots we even find examples of raised-relief slip-trailing.  Slip-decoration with a transparent glaze became the surface decoration of choice on Byzantine pottery, and with Byzantine and Ottoman imperial expansion, the technique traveled into the Balkans and Eastern Europe.

Traditional crafts throughout Eastern Europe often display elaborate surface decoration, including slip-trailing and feather-combing on pottery.  My father was full-blooded Czech, and from a young age I gravitated towards intricate decoration found in Eastern European crafts.  Around 1980 in my studio, Railroad Stoneware, in Blue Lake, California, I started doing slip-trailing and feather-combing as a diversion from production utilitarian ware.  I was shifting my studio production to one-of-a-kind slipware when, in 1985, my wife and I made the decision to attend graduate school in Massachusetts.  For the next ten years I did colored clay work, but resumed slip-decoration during my first few years running the clay program at the Appalachian Center for Crafts.  Some examples below are from 1980 to 1985 in California, and others from 1994 to 1998 in Tennessee.

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Decorating Slips

For slip decoration, I always start with a white base slip.  The Utah State University STA (Sticks to Anything) Decorating Slip (click here for the recipe PDF) is a popular white base slip.  I add ceramic oxides (as specified on the same PDF) or Mason stains for color.  Most of the common decorating slip recipes are based on traditional cone-10 porcelain claybodies, which are usually fluxed only with potash spar.  When used as a decorating slip, such recipes can result in problems with peeling and separating in the firing.  All-temperature decorating slip recipes like the STA are adapted by replacing part of the potash spar with a combination of lower temperature fluxes including a midrange flux such as nepheline syenite and lowfire flux such as Frit 3195, improving slip adhesion throughout any firing range.  Problems with slip-decoration separating from the base clay generally occur as the kiln passes through early red heat and the claybody and slip shrink at slightly different rates.  Addition of a the low-melting flux (either borax or a calcium-borate frit like Ferro 3195) improves the bond at the interface between slip and body just as firing shrinkage begins.  Also, the slip is deflocculated, greatly decreasing drying shrinkage and thus reducing chances of the slip separating during drying or firing. All of the pieces pictured above were reduction-fired to cone-10 in a downdraft gas kiln.

Slip-Trailing Applicators

Most of the slip-trailing seen here was done with rubber ear-syringe bulbs cut back at the tip and equipped with trimmed basket-ball-inflating needles and a short length of very fine plastic tubing. The inflating needles come with the hole on the side near the end, which won’t work in this case.  To adapt basket-ball-inflating needles for slip trailing, straighten out a paper clip, insert it all the way into the needle from the back end, and use wire cutters to snip off the tip including the side hole.  The paper-clip wire keeps the tube from collapsing when you cut it.  Lightly sand the end of the cut needle to remove the burrs.  This setup will work with just the modified ball-inflating needle affixed in the ear syringe bulb, but is less likely to gouge the clay surface if equipped with a short extension of very thin, flexible tubing.  1/16″-inside-diameter medical I-V tubing is ideal.  Lacking that, very small heat-shrink tubing (available from electronics or auto parts stores) will also work well. In the latter case, place one end of a one-inch piece of the heat-shrink tubing over the end of the ball-inflating needle, and then shrink the tubing with gentle heat from a propane lighter, candle, or stove flame.

Currently, my favorite slip-trailing vessels are the plastic bottle applicators offered by Xiem Studio Tools.  At their website, click “Precision Applicators” on the left and scroll down to select the ones best suited to your needs.  The plastic bottles are far less expensive than ear syringe bulbs or Xiem’s rubber-bulb applicators, equally effective, and far easier to fill, use, and clean.  Slip decoration often involves switching back and forth between many colors of slip, and that gets very expensive with multiple rubber bulbs.  With the Xiem plastic bottles, you can inexpensively purchase multiple bottles, caps, and precision tip sets to suit your needs.

Tools for Feather Combing

There is some misunderstanding about the technique known as feather-combing. The name comes from the combed pattern’s resemblance to a feather, not from the use of a feather as a tool to manipulate the slip.  Any flexible, fine-pointed tool will work, and the objective is to create enough friction to pull the liquid slip colors in order to attain the classical combed effect, but without digging into the clay substrate beneath.  My favorite tool is a short length of 50-pound-test monofilament fishing line affixed to a thin wood dowel handle with a piece of duct tape.  For a neater look, drill a small hole in the end of the dowel and affix the monofilament with a little glue.  The tool works best if the monofilament extends from the dowel about an inch and a half.  The cut monofilament is sharp enough to rake up clay from the substrate, but you can round it off by barely holding the tip close to a torch or lighter flame.  If you find that the monofilament does not pull the slip colors satisfactorily, hold the tip close to a lighter or torch flame a little longer and melt the end to form a tiny ball.