Ida Pauken, who was a student in the Ceramic Arts department at Richland College in Dallas, Texas, designed and made a handy little extruder. She created it after a number of discussions with her instructor, Fred Sweet, about the possibility of using a caulking gun as an extruding device.
There are two basic types of tube support on caulk guns: those with sheet metal cradles and the more expensive twin-bar type. At Richland, they use the type with the sheet metal cradle most often to make extruders. The cradle makes loading and unloading easier for some people, since they can put downward pressure on the PVC tube when pulling back on the plunger rod, and they can use the cradle to support the tube when inserting the die between the tube and the end cap/plate.
Modifying a Caulking Gun
The end of the caulk gun has a slot or notch to hold the nozzle of the caulk tube. Unless you want to make only very narrow coils, you need to cut this slot open to a more round shape with a jeweler’s saw. Finish the opening with a half-round metal file to get the burrs off, both for safety and to better set the die against the end cap.
For the extruder barrel, use a medium- to thick-walled PVC pipe, chosen for its interior diameter, which should closely match the plunger plate of the caulking gun. Thin-walled tubing should work if the interior diameter agrees with the plunger plate.
Cut the ends of the PVC pipe squarely and sand them smooth to prevent excessive leaking between the die and the end of the barrel.
Most PVC pipe is not perfectly round or smooth in the bore. It may contain some bumps and drips. This can be rectified or refined in most cases by running the plunger back and forth in the empty barrel, scraping the flaws away. If the flaws are excessive, get a better piece.
Insert dies between the end of the PVC barrel and the modified slot at the end of the gun. Pressure seems to seal most of the leaks. If the barrel is cut squarely and sanded smooth, leaking will be minimal. Tip: If the clay blows back over the plunger plate, a small wad of dry cleaner bag placed in the barrel between the clay and the plunger plate usually solves most excessive leaking.
Unmodified fender washers of various interior diameters make excellent dies for this extruder. However, using a jeweler’s saw, it’s relatively easy to adapt their original shapes. If you happen upon washers with square interior holes, perhaps intended for use with carriage bolts, they will make nice, solid square forms. If the barrel length is cut back an additional ½ inch or so, Lexan, Plexiglas, or plywood could also be used. Ida also tried using waterproof epoxy to glue other pieces of materials to the “washer” die to block part of the original opening. These additions should face back into the barrel, giving extra support to these attachments by the pressure of the moving clay. Some potters have found cookie press dies in flea markets and garage sales, which also work and are a source of non-round openings.
For cleanup, use a bottle brush for cleaning baby bottles. A dish towel threaded through the barrel works as well. Remember that WD-40 or equivalent applied to the inside of the barrel before loading the clay makes clean up easier. Occasionally lubricating the handle mechanism also makes the job easier.
Given that you’ll most likely be making small-diameter extrusions and that you’re relying only on the strength of your grip, this extruder works best with clay that is well wedged, fairly moist, and low in grog.