DIY Network

Glazing the Bowls Glazing the Bowls From "Throwing Clay" episode DTHC-102

Figure A

In preparation for the glazing process, Bill Van Gilder has applied wax-resistant emulsion to the bottom of the bowl, and now he's ready to apply the glaze (figure A).

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1. Prepare a black glaze. Keep in mind that glazes at the liquid stage do not appear the same color as they do dried. Black and amber glazes appear red when liquid, so it's essential to keep glazing buckets labeled to avoid confusion (figure B).

2. Dip the pot for three seconds and allow it to drain. Where your wet fingers have held the pot, patch the clay with a fingertip dipped in the glaze. Remove excess glaze clinging to the wax with a wet sponge; this prevents it from contaminating the second glaze (figure C).

3. To break up a solid line that would occur if the bowl is dipped straight down in the second glaze, Bill grips the bowl with his fingers placed along the center of the bowl. The impression left by his fingertips adds interest along the glaze line (figure D).

Figure B

Figure C

Figure D

4. Set the bowl aside to dry before placing it in an electric kiln for the glaze firing. During the firing, the pots cannot touch; if they do come in contact with each other, the glaze will fuse the pieces together.

A Few Notes on Firing

Bill uses both electric and wood kilns, but electric kilns are much easier to use: just flip a switch, and the kiln is ready to go.

Wood firing, on the other hand, is a complex art, one he has been perfecting for 20 years. The firing is planned three to four months in advance, and for Bill and his potter colleagues, it's a community affair. The firing process is labor intensive, as it involves heavy manual labor, including approximately five cords of wood, cut to length, split and stacked (figure E).

Pots are made about eight weeks before firing, using special clays prepared to absorb the flashing and texture of the fire as it moves through the clay. Slips and glazes are prepared for the firing, and thought is given to how the clay will be placed in the kiln; specific pots are made for specific parts of the kiln (figure F).

Figure E

Figure F

Loading the kiln and constant management of the fire is crucial to the firing process. If the fire rises too quickly, it can damage the pots. The temperature needs to rise approximately 100 degrees an hour, the time being limited to 24 hours to complete the firing process (figure G and figure H).

Figure G

Figure H

At the end of 24 hours, the kiln temperature is 2,500 degrees. Next, it must be cooled quickly by 200 degrees, and the kiln must be kept tightly shut for 48 hours. A wood fire is hard on clay, but the flames give an extraordinary surface to the clay as long as the process is correctly set up and executed.

In two days the kiln temperature should have cooled to 150 degrees, and the kiln can be opened. When the pots have cooled, they are unloaded, and the results of the firing can finally be viewed (figure I and figure J). (By contrast, an electric kiln fires for 10 to 12 hours and cools for another 24 hours before it can be unloaded. )

Figure I

Figure J

Figure K

For more than 5,000 years, potters have produced expressive, subtle surfaces by wood-firing their wares. Bill's electric-fired dish is both beautiful and functional: not only can it serve a decorative purpose, but it can also be used as a baking dish in the oven or microwave and then be brought straight to the table as a serving piece (figure K).

RESOURCES :

Kilns
L & L Kilns
Website: www.hotkilns.com

Clay
Highwater Clays
Website: www.highwaterclays.com

Extruders
American Art Clay Co. Inc. (AMACO)
Website: www.amaco.com