Wednesday, April 25, 2012

Charles Sweigart of Reinholds, Pennsylvania tells this story about marbles

Many years ago I observed first hand some large 3-4” diameter glass marbles/carpet balls being polished. They were all created years before and were purchased later in a closeout sale. No internal or external defects were visible. When placed in a 3 armed machine with rotating rubber cups coated with a wet slurry of polishing compound and each cup rotated against the sphere, they were polished over 1-2 hours time. A large number of the spheres would suddenly crack/check internally and sometimes externally as well. I am sure that incorrect annealing caused the internal stress that was let loose. If one was found without knowing what occurred the external damage would be described as a crack, the internal damage would be called a heat check by some, but how does the knowledge of exactly what and when it occurred influence the names used to describe the flaw.

www.cardersteubenclub.org

2012 Carder Steuben Club annual Symposium will be held at The Corning Museum of Glass in Corning, NY from September 20-22, 2012.

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