As we all know, glaze defects are not all bad. Ceramic artists can use them to great effect on both pots and sculptures. Most are not safe for surfaces that come in contact with food, but as long as food surfaces are avoided, these glazes can be quite beautiful on a pot.
In today’s post, Deanna Ranlett shares the results of layering a lichen glaze with a translucent base glaze, and best of all she provides the cone 6 glaze recipes! – Jennifer Poellot Harnetty, editor.
Chances are, like me, you’ve relegated lichen, crackle, and crawl glazes to your special effects file, thinking of them as only to be used to create weird, snow-like, not-at-all-food-safe surfaces. We’re normally trying so hard to correct for glaze defects like crawling and crazing that we think, “why on earth would we want to achieve that?” Also, because of their food safety issues, many of us sideline these types of glazes for sculptural or decorative use only. For surfaces that don’t come into contact with food, these glazes are great for adding visual and physical textures.
There’s a wide range of lichen glaze recipes available with sub-categories such as crawls, crackles, and crazing glazes—some result in a dry, crackled surface; some give a glossy, pearly effect similar to tooth enamel; and some create snowflake patterns.
Commercially, there are many options for lichen glazes at low-fire temperatures—some can be used on bare clay and some can be used in conjunction with other glazes. There are few options available commercially for cone 6, so that’s where we began our pursuit: a lichen glaze recipe that gives a glossy surface but still maintains a distinct separation while staying adhered to the pot.
We wanted a recipe that didn’t need a special or altered firing cycle and could be fired in the kiln alongside other cone 6 work.
In the glaze chemistry class here at the shop, we recently tested several reticulated cone 6 glaze recipes and then pushed the experiment further by layering them with other translucent base glazes. We got some pretty surprising and fantastic results. We layered the lichen glazes both on top of and underneath the base glazes (two different Chun recipes with different stains added for color). The samples with the lichen glazes underneath the base glazes were not so exciting, but the samples with the lichen glazes applied over the base glazes were very striking—much more so than I originally predicted. The lichen glaze adds a shimmering quality to the glaze underneath when applied in a single coat, two coats give a delicate crackled surface, and three coats give more separation between crackles and a larger crawl pattern. Up close, there is an almost silvery or pearlescent effect that is very lovely.
This layering technique is useful for creating a visual texture on a solid surface and also for creating a crackle-like effect where you might not normally use a crackle. The results using the lichen glaze on top of the base glaze were equally beautiful over areas with and without texture. Our favorite samples resulted from using the more subtle glazes (light greens and blues) and applying them over textured tiles. This combination allowed the lichen glaze to break over the raised parts of the texture and rest in the recesses, giving it a lovely, lace-like effect.
Lichen glaze recipes include a large percentage of magnesium carbonate and the resulting mixed consistency is very fluffy, similar to frosting. The glaze is thick but brushes on thin and smooth. Do not mix this glaze too thin; when it’s mixed properly, the result is an almost non-existent crackle pattern when you apply the first coat. When you apply the second and third coats, you can start to see the patterning appear. Take care when handling the pieces because the glaze the has already begun to crackle and can easily be chipped off of the surface before you get it into the kiln.
Different application methods of lichen glazes result in different surfaces. It helps to brush them because it’s easier to control the effect of the glaze. If applying over another glaze, first dip the piece into the base glaze, let it dry, then brush the lichen glaze on top. The resulting crackle effect and the size of cracks varies based on the direction of the brush stroke. The base glazes below work for both brushing and dipping. Add a small amount of CMC or Veegum-T to aid in their brushability.