Upcycling Glaze Waste Deanna Ranlett

Appears in the Jul/Aug 2015 issue of Pottery Making Illustrated.

I am always on the hunt for new surface tips and tricks. We’ve all had dried up jars of underglaze or glaze, a container lid that is crusty, or a bucket left uncovered by accident. Here’s an interesting way to use up those materials and a great alternative to washing them down the drain or dumping them in the garbage.

Crushing and Sorting

I started by crushing up my dried materials and sorting them by type (commercial underglazes, commercial glazes, and homemade glazes) and cone temperature into individual mixing cups (1). Caution: Always wear a dust mask and work in a well-ventilated area when crushing dried glazes.

Immediately there is a noticeable difference: commercial products were hard to break up due to the addition of hardeners while homemade glazes crumbled easily. I crushed the chips to between ¹⁄₈ –¼-inch-sized pieces similar to the chunks found in commercial crystal glazes, which range in size to create a variety of effects. You can vary the size and shape of your chips to your preference.

Pressing into Clay

To see how the chips would behave when pressed into wet clay, dried, then fired, I rolled the chips into leather-hard tiles using a small wooden rolling pin, then bisque fired the pieces to cone 04 (2). All of the materials bisque fired solidly into the tiles and were not muddied when brushed and fired with clear glaze (3).

I found that Mayco’s Stroke & Coat glaze chips were harder and broke easier, while the commercial underglazes and homemade glazes broke into thinner chips. Different brands also have different melting points. For example, Spectrum’s underglazes and Mayco’s Stroke & Coat glazes fired glossy in the bisque firing. Even some of my homemade cone 6 glazes melted a little bit at cone 04. This would have ramifications if the chips were too close to the bottom of a piece when firing.

Mixing with Slips

Next, I used a white slip, mixed the chips into it, and applied it to leather-hard clay. I tried this technique because I wanted an irregular, raised surface with a more dramatic texture. When fired with a clear glaze to cone 6, the look was more erratic and gestural than the pressed-in chips. When mixing the commercial products into the slip, most didn’t dissolve too quickly to be brushed on, but the homemade glazes didn’t survive mixing without dissolving and had to be sprinkled onto the surface between layers of slip. These tiles are particularly intriguing to me because some of the chips became pebbly and others turned glassy.

Mixing with Glazes

Next, I decided to try the chips mixed into colored homemade glazes—a Chun white, a marigold yellow, and a deep, licorice black. The nature of the liquid glazes led me to try a sandwiching technique. If I mixed the chips into the glaze, they dissolved too quickly, making streaks. So, instead, I brushed on two coats of glaze, then sprinkled the chips onto the wet surface, and finally covered them with a third layer of glaze. You could also sprinkle the chips on top of the third coat of glaze.

In the white glazed tiles, some chips stayed more raised, but most pooled into the glaze, which was a great effect as it spread (4). With the marigold glazed tiles the effect was very similar to the white glaze (5). The colors really popped on the light and yellow glazes. In the darker black glaze, I found the underglaze chips got a bit lost (6). Perhaps sprinkled on top they would have shown off better. The recycled homemade glazes stand out well when mixed into the black glazes. The chips bloomed in the glaze and gave a unique soft-colored, crystalline effect.

Conclusion

I think this is a fun and interesting way to use dried-up glazes, that would otherwise be discarded, to create intriguing textural and colored surfaces. 

Future testing ideas could include using colored slips mixed with the chips to create further dimension and depth or combining low-fire products with high-fire ones.

Caution: Be sure to test all materials and combinations first before using them on your valued pieces and be sure to protect your kiln shelves and bricks from potential running glazes.

Deanna Ranlett owns MudFire in Decatur, Georgia (www.mudfire.com).