Types of damage caused by various cracking and crushing methods used for measuring egg shell strength

Abstract

The damage caused to egg shells by various cracking and crushing methods was examined in two ways. Externally visible damage was photographed, while internal damage was studied in thin sections of shell prepared after embedding in plastic. With the flat plate, flat‐ended peg and round‐ended peg the shell may crack cleanly over some distance or crack and crumble outwards from the first point of damage. The needle pierces the outer layers of shell and pushes out a cone from the inside of the shell. A falling ball produces clean cracks or damage rather similar to the flat‐ended Peg. When the treatment is stopped before visible damage occurs there is usually a considerable amount of internal damage of a kind which could lead ultimately to the type of damage actually observed. The first sign of change appears to be the formation of twinning planes in the individual calcite crystals. Later the large crystals may break up into small units.