WHY:
1. Glass is considered a brittle solid. Brittle is defined by dictionary.com as, "having hardness and rigidity but little tensile strength; breaking readily with a comparatively smooth fracture, as glass." This means that, when pressure is applied, glass will break before it bends. In the case of excess force to your milk bottle, a crack would be foreseeable.
2.Glass also fluctuates (only slightly) during temperature change. Significant temperature changes (like running a recently used coffee pot under cold water) causes these fluctuations.
3.The expansion of liquid or material inside of a glass product (due to freezing) causes increased pressure against the glass walls. It is recommend to only fill a glass bottle 90% (or less) full to accommodate for expansion. SMC fills milk bottles completely full, however, which leaves no room for the bottle to expand! The excess force from increased stress is the number once cause of SMC glass bottle breakage.
HOW TO PREVENT IT:
Preventing bottle breakage is easy! Simply remove your products from your cooler soon after they are delivered. The only method to reduce/eliminate fractured milk bottles is to react before it can happen. Too harsh of temperature change can also busy glass, so do not add any heated items to your porch box/cooler
