Tuesday, July 19, 2011

Earthenware, Stoneware, and Porcelain

An English earthenware plate from our family collection.

In our family collection, we have all three of the major ceramic categories:  earthenware, stoneware, and porcelain.  The stoneware and porcelain are non-porous ceramics and this means they usually present no staining problems.

I sent a picture of one of our ceramic plates to Kory Berrett of Berrett Conservation Studio for his advice on long-term care.  Kory responded that this particular plate is earthenware – and therefore staining should be a concern.

According to Kory, “The plate you’ve illustrated is an English earthenware that was decorated using the transfer method.  The pattern is printed on tissue using an ink made of glaze ingredients, put on the plate something like a decal, and then fired to set the colors and burn off the tissue.  Sometimes you can see edges where the pattern was cut or wasn’t well fitted.

“Since this plate is earthenware, it is porous and thus vulnerable to staining.  This often happens during the period of use if the surface is cracked or not well sealed by the glaze and there is prolonged exposure to offending liquids like grease.  Staining can sometimes be removed but is more often dealt with by bleaching.

“As for storage of ceramics, they tend to be fairly forgiving as long as they are protected from accidental breakage and are wrapped with stable contact materials like acid-free tissue, ethafoam, and bubble wrap.  Newsprint and kraft papers can stain earthenware as the paper ages.”

© 2011 Lee Price

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