Yes, newer mason jars have a microwave-safe symbol on them. It is important to keep in mind that glass mason jars are non-reactive but still become very hot to the touch. For this reason, it's best not to package anything that requires long periods of microwave heating in mason jars. Use mason jars for quick-heat items like pre-cooked pasta, soup, cheese dips and other products that only require a few minutes to heat.
If your company packages freezable products in mason jars, disclaimers should be included that inform consumers not to thaw them in the microwave. Super-heated areas of glass may crack or shatter if the contents expand the jar. Metal rings, lids, and caps used to seal mason jars are not microwave safe.
Dishwashing
Mason jars can be cleaned in a dishwasher. However, repeated dishwashing may scuff the surface. For older jars, you may want to hand wash them to keep their appearance.
Oven
Mason jars are not designed for use in the oven. Empty jars may be sterilized in an oven but they should not be used for baking or oven cooking.
Freezing
Some mason jars have a freeze line embossed on the glass surface to show the limit of the contents for freezing applications. As a general rule, product should be filled to just below the collar of the jar. This is to prevent cracking of the glass due to expansion of the product during freezing.
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