Yes, you can generally put glass mugs in the freezer, but you need to follow some precautions to avoid damaging the glass or causing it to shatter:
Use tempered or freezer-safe glass: Not all glass mugs are suitable for freezing. Make sure the glass mugs you are using are labeled as "freezer-safe" or made from tempered glass. Tempered glass is designed to withstand temperature changes and is less likely to break when exposed to freezing temperatures.
Allow room for expansion: Liquids, especially water, expand when they freeze. When placing glass mugs in the freezer, leave some room at the top to accommodate the expansion. If the mug is filled to the brim, it may crack or break as the liquid freezes and expands.
Avoid sudden temperature changes: If the glass mug is at room temperature, do not place it directly in the freezer. The rapid change in temperature can cause thermal shock and lead to the glass shattering. Instead, let the mug cool down gradually before placing it in the freezer.
Wrap or separate the mugs: If possible, wrap each glass mug individually or separate them using a towel or cloth to prevent them from knocking into each other and potentially causing breakage.
Avoid extreme temperatures: While most glass mugs can handle freezing temperatures, extremely low temperatures, such as those in industrial freezers or dry ice, could still cause damage. Stick to regular household freezers, and you should be fine.
Thaw slowly: When you're ready to use the glass mug, allow it to thaw slowly at room temperature or by placing it in lukewarm water. Avoid using hot water or placing it directly in the microwave, as rapid temperature changes can cause the glass to crack.
While glass mugs can generally withstand freezing temperatures, it's always a good idea to check the manufacturer's guidelines and recommendations for your specific glassware. Following these precautions will help ensure the safety of your glass mugs and prevent accidents or breakages.