Saturday, February 16, 2013

Word of the day- Striking

STRIKING- "The practice of forming Cu nuclei at the maturing temperature, followed by rapid cooling to room temperature. By subsequent heat treatment at an appropriate temperature, the nuclei will grow into little cristallites of the right size to give reds." pg 466 Ceramic Glazes by Parmelee who is quoting Norton.

-This is typical in glass making where you "strike" glass colors which means - mature to target color when fired.

-In ceramic firing- striking can be either firing to peak temperature, (either in reduction or oxidation)  and on cooling, reigniting the kiln and putting it in reduction between 1300 F and 1500 F and holding the reduction for a period of one to several hours. (often done with copper reds.) (see image above.)

[Pete Pinnell had a nice article in Clay Times many years ago where he took tiles of copper red glazes out of the kiln every hour and he found the the red did not develop until around 1400 F with his draw tiles. But when he put the same tiles back in the electric kiln and "struck" them to 1600 F or so, they developed color. Indicating that it takes time for the red color to form.]

-Or allowing the pots to cool and then refiring to 1500 F or so in a reducing atmosphere. (often done with crystalline firings. ) 

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