Making Glaze “Test Tubes” with an Extruder

Nicole S. Young Ceramics, Extruder, Glaze, Kiln, Pottery, Studio 7 Comments

After setting up my studio, I wanted to create test tiles to work with some of the Coyote glaze samples I have. I was originally going to do flat tiles, but after finding this pin on Pinterest I decided that extruding small tubes would give me a better visual on what the glaze would do to the curves and corners of a piece. It also allows the glaze to run down the tubes and show how it works on upright pieces, such as mugs.

While making them, I thought I would take photos and do a step-by-step on the process in case anyone is interested. Here it is!

Step 1:Set up a hollow die in an extruder. I’m using the North Star stainless-steel extruder with the small octagon hollow die.


Step 2: Extrude several tubes as needed. Let them sit as long as they need until they are still soft, but firm enough to handle without getting squished or deformed. If the clay is really soft then you’ll probably have to let them sit for a little while. Some of the clay I worked with was pretty firm (but still soft enough to be pushed through the extruder) so I didn’t have to wait at all.


Step 3: Set a miter box on the edge of a table (you can get it at a hardware store), cut a rectangle of foam to fit, and then place more foam on the end for the “flow-over” clay so that it doesn’t bend while going through the miter box.


Step 3: Use a wire cutter inside of the miter box and cut into 3″ lengths. This will allow you to cut fairly straight cuts very quickly. And, the foam underneath helps prevent it from warping. (Tip: push the wire through and down into the foam to get a clean cut.)


Step 5: Stamp one end (the end that is on top). This helps to see what the glazes will do over textured surfaces. And, if you are testing more than one clay, use different stamps for each clay to tell them apart.


Step 6: Poke holes to allow for hanging. Make sure that the hole is on the opposite side and opposite end of the stamped area.


Step 7: Dry until bone-dry. Be sure to set them upright on the “hole-side” the whole drying and firing process to make sure it stands up properly in the kiln during the glazing process.


Step 8: Bisque fire the test-tubes. Then, when they are fired and cooled, organize them into types of clay (or whatever works for your system).

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Step 9: Glaze each tube according to your setup. I used Coyote 4 oz sample containers filled with glaze, labeled them with numbers, and wrote the number on each tube before I dipped it. I had a nice “assembly line” that went something like this:

  1. Get one tile from each type of clay and line them up side-by-side.
  2. I selected a glaze container and wrote a number on the top of the lid.
  3. Using an oxide stain and a tiny brush, I wrote the number of that glaze on each tile near the hole.
  4. Then, I went through and dipped each tile in the glaze.
  5. I did these steps 40 times until I had them all glazed!

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Step 10: Glaze-fire the kiln. I set my Scutt 1022 to Cone 5, Medium speed, with a 20-minute hold at the end.


Step 11: Put them on display for the world to see! :) Here I have a simple peg-board with some hooks holding each of my tubes. The peg-board I have installed wasn’t long enough to hold all 40 glazes, so I just picked out some I wasn’t too thrilled with and kept the rest on the wall. (I also don’t have enough hooks yet … still waiting on my hardware store to get more in since I cleaned them out yesterday!)

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Overall, I won’t have ALL of these glazes on-hand to use with my future work. I did this to find the ones I really wanted to start with, and so then I picked out five glazes (plus a clear glaze) and mixed them up to start with. Over time I expect to add more glaze buckets to my collection.