Big Ceramic Store Blog

Sgraffito in Terra Sigillata With BCS Customer Lisa Harnish - Conclusion

BCS customer Lisa Harnish shares her amazing techniques and recipes for "Sgraffito in Terra Sigillata-Part 2" in today's post! Visit Lisa's website for more!

Lisa Harnish first began working with clay in January 2002. Her initial education in ceramics began at Chandler Gilbert Community College, and continues to this day. Lisa’s sgraffito designs take their inspiration from nature, such as grass, leaves, seaweed and vines that wind their way around and across the vessel. 

Did you get a chance to read Parts 1 & 2 of our series with Lisa? If not, you may want to read them as well, as they cover making the sig, painting it on, and decorating. Today we will go over to burnish or not to burnish, and glazing if you want, finishing up the series.

To Burnish or Not To Burnish

One of the prized qualities of Terra Sigillatas, is the lustrous smooth satiny surface that can be achieved when it is polished or burnished.

Once the terra sig has been brushed on, and is dry enough to not leave any finger prints when touched, you can rub the surface to smooth it and make it shine lightly. Fingers alone work, but soft cloth, or a piece of plastic bag work better (less friction on sensitive fingertips).

Polished stones, spoon backs and numerous other tools also abound, for burnishing. Gentle rubbing will produce a nice polish. A true “burnishing” with a smooth rock, spoon back, or other hard surface, will compress the surface, locking the microscopic platelet particles into a hard smooth surface.

I generally do not bother to polish or burnish sgraffito pieces, since I prefer to fire to cone 6 or cone 10. Glazing over the terra sig makes it pointless, as does high firing, which burns out the burnished surface.

A burnished patch of sig may also crack or sinter off the surface during the carving stage of sgraffito however; burnishing is a great effect for low fire treatments such as naked raku, or pit firing.

Glazing, a.k.a, Committing Heresy

Once upon a time, applying a glaze OVER a terra sigillata would be considered a heresy by many ceramic artists.

Traditionally, terra sig surfaces were intended for low fire temperatures (oxidation in electric kilns, pit firing, raku firing, or flashing colors in wood firing). In my opinion... rules were made to be broken right? Besides, there is no such thing as the Pottery Police!

I have found that using glazes, in combination with colored terra sigs, produces a unique surface, and glaze bases that are highly reactive to colorants, and colorants that are highly responsive in glaze, can produce a variety of beautiful and unique results!

Thank you Lisa! You have given us a great taste of the possibilities with Sgraffito in Terra Sigillata!

If you'd like to share your ideas, projects or submit a post for our blog, email us at! We look forward to hearing from you!


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