Glossary

Freeze Drying Glossary

The operator’s vocabulary used throughout this site, defined plainly.

Sublimation

Ice turning directly into vapor without melting — the physics the whole machine exists to exploit. Under deep vacuum, frozen water leaves the food while the structure stays intact.

Pre-freeze

Freezing loads solid (ideally in a chest freezer) before they go in the machine. Saves the freeze dryer hours of doing what a freezer does for pennies, and improves consistency.

Dry cycle

The main phase: vacuum pulled, trays gently heated, ice sublimating away over many hours. Cycle length depends on food type, load weight, and how wet the food started.

Final dry

The finishing phase that chases out remaining moisture. Extending final dry is the standard answer to a load that fails the dry check.

Load weight

Total food weight per batch, logged per tray. The single best predictor of cycle time for a given food — which is why the batch log starts here.

Tray density

How thickly food is spread on each tray. Even, moderate density finishes evenly; piled trays hide wet centers that fail the dry check.

Vacuum pull-down

The pump pulling the chamber to operating vacuum at the start of a cycle. Slow pull-down is often the pump’s way of asking for an oil change or a door-gasket check.

Oil change (pump)

Routine replacement or filtration of vacuum-pump oil on oil-sealed pumps. The core maintenance habit of ownership — neglect it and the pump tells you, then bills you.

Residual moisture

Water remaining in food after a cycle. The enemy of storage life: the dry check exists to catch it before packaging does the hiding.

Dry check (snap test)

Verifying doneness: thick center pieces should snap or crumble, never bend or feel cool/moist, with weight loss matching your log for that food. Fails go back for more final dry.

Mylar

Metallized barrier bags used for long-term storage of freeze-dried food, sealed with an impulse sealer, normally with an oxygen absorber inside.

O2 absorber

An oxygen-scavenging packet sealed into storage bags to slow oxidation. Sized to the bag volume; stored airtight between uses because they spend themselves in open air.

Rehydration

Returning water to freeze-dried food before eating. Quality varies by food — part of why honest per-food verdicts beat blanket claims.

Candy mode

Running the machine warmer without a freeze phase for candy experiments — puffed, crunchy results, and tray cleanup the videos don’t show.

Batch economics

The honest math of what a load costs (power, consumables, time) against what it preserves. Depends entirely on whether real harvests and real meals feed the machine.