Mylar & Oxygen-Absorber Calculator

Read before you seal anything

• Never: Only use oxygen absorbers with foods under about 10% moisture. Sealing a moist food in a low-oxygen container creates the anaerobic conditions Clostridium botulinum needs — a botulism risk (National Center for Home Food Preservation framing; USU Extension). Dry it first or preserve it another way.
• Never: Never use oxygen absorbers with sugar or salt. The absorber's moisture-activated iron chemistry turns them into a solid brick (USU Extension; Wallaby Goods guidance). Sugar and salt store indefinitely in a sealed container with NO absorber.
• Know: Absorbers start working the moment their factory pack is opened and are spent within a few hours in open air (USU Extension). Open one pack per packing session, work fast, and reseal unused absorbers immediately in a small airtight jar — an opened absorber left out overnight is dead.
• Know: Good candidates (under ~10% moisture): grains, white rice, dry beans, flour, pasta, rolled oats, and properly dried vegetables. Bad candidates: brown sugar, raisins and moist dried fruit, jerky, and anything that still feels pliable.

1. Stage everything first: 4 containers, food, sealer or clothes iron, marker, and labels — absorbers come out LAST.
2. Confirm the food is dry (under ~10% moisture): grains, rice, beans, flour, pasta, oats, or crisp-dry vegetables.
3. Fill each container, tapping to settle, leaving about 1 inch of headspace for the seal.
4. Open ONE absorber pack and drop 1 × 2000cc into each container (spent absorbers feel warm and rigid — a fresh one is soft).
5. Press out as much air as you can, then heat-seal the Mylar (or lid the jar) within minutes.
6. Reseal any unused absorbers immediately in a small airtight jar.
7. Label each container with the contents and today's date.
8. Check the next day: a good Mylar seal pulls tight and brick-like as the absorber finishes; a still-loose bag needs a fresh absorber and a new seal.