Print, Photographic

Black and white photographic print mounted on fabric depicting equipment in the research laboratory at the Champion Spark Plug Co.
Caption reads: Photograph 35
Small apparatus for quick determination of thermal expansion of porcelain. The specimen to be tested is held in a frame made of material with minimum expansion, and so arranged that as the porcelain expands it tilts the mirror. The deflection of a beam of light thrown against the mirror is accurately measured by means of a telescope and scale as the temperature of the porcelain is increased, the temperature of course being also accurately measured.
A high or low thermal coefficient of lineal or cubical expansion has marked effect on the behavior of a porcelain core and must be studied carefully.