Actually, all Food Vac bags are is THICKER MIL than freezer bags, which are thicker than sandwich bags. They are ALL made of the same plastic, folks! Food Vac bags, which are what is used in the http://en.wikipedia.org/wiki/Sous-vide method, wether or not they are called vac bags. The key is that they are thick and rated for submerging in simmering water. Freezer bags are thinner, so shouldn't be submerged in boiling water - they can soften.
All are rated for use in microwaves, opened, as well.
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