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These tri-layer bags (plastic inside and out, with a foil middle
layer) are a nominal "half-pound" size and are
great for the homeroaster's gift-giving. They're 3-1/4" x 10"
in their flat state and have side gussets.
They can be sealed with a standard impulse sealer, or
failing that, a household clothing iron (set a bit cooler than
synthetic worked fine when I tried it). Even left empty enough to leave the valve exposed for the photo, this bag contains 200 grams, or just over 7 oz. The bag will easily hold 10 oz. of beans at this degree of roast (a couple of 2nd crack outliers), though probably 8-9 oz. is a more realistic capacity for darker roasts. Why Valves? Coffee's worst enemy is oxygen. The sooner you can get it bagged, sealed, and vacuumed, the less oxidation can occur. Since coffee beans give off roughly two-and-a-half times their volume in CO2, a completely sealed bag will explode. That's where the one-way valve comes in. It allows the CO2 to escape while preventing oxygen from entering. |