Analysis of information sources in references of the Wikipedia article "Bologna bottle" in English language version.
making Bologna Vials.
The bottle is tempered in such a way that the outside surface is experiencing compression and the inside surface is experiencing tensile stress. Since it is very hard to start a tear in a layer that is being compressed, it is hard to tear the outside of the bologna bottle. But the inside is under tension and the slightest injury to it will cause the surface to tear itself to shreds.
The bottle is tempered in such a way that the outside surface is experiencing compression and the inside surface is experiencing tensile stress. Since it is very hard to start a tear in a layer that is being compressed, it is hard to tear the outside of the bologna bottle. But the inside is under tension and the slightest injury to it will cause the surface to tear itself to shreds.