二. Bottle Manufacture 2. Annealing ⚫ Purpose-to reduce internal stresses; in annealing oven ⚫ Reasons- Walls are comparatively thick and cooling will not be even. The inner and outer skins of a glass become rigid The still-contracting inner portion build up internal stresses Uneven cooling develop substantial stresses in the glass. ⚫ Bottle passes through an lehr after removal from the blow mold. ⚫ Steps : glassware is carried on a moving belt temperature is raised to about 565°C gradually cooled to room temperature with all internal stresses reduced to safe levels.(about an hour) ⚫ Improperly annealed bottles are fragile and high breakage ⚫ Hot-filling also produce unacceptable breakage levels.二. Bottle Manufacture 2. Annealing ⚫ Purpose-to reduce internal stresses; in annealing oven ⚫ Reasons- Walls are comparatively thick and cooling will not be even. The inner and outer skins of a glass become rigid The still-contracting inner portion build up internal stresses Uneven cooling develop substantial stresses in the glass. ⚫ Bottle passes through an lehr after removal from the blow mold. ⚫ Steps : glassware is carried on a moving belt temperature is raised to about 565°C gradually cooled to room temperature with all internal stresses reduced to safe levels.(about an hour) ⚫ Improperly annealed bottles are fragile and high breakage ⚫ Hot-filling also produce unacceptable breakage levels