Storage & stability reference
Pinned in #storage-coldchain. Assembled from what members reported actually happened, not from a manufacturer insert.
The reference range
2 to 8 °C. The problem is that most domestic fridge doors are not in that range. Members who have measured report door shelves running four to five degrees warmer than the back of the middle shelf, and swinging by several degrees every time the door opens. A five-pound thermometer settles the question, which is how the fridge-thermometer joke in #off-topic started and why it will not die.
What has survived what
| Condition | Lyophilised powder | Reconstituted solution |
|---|---|---|
| 2–8 °C | Fine, long term | Fine, weeks |
| Room temperature, hours | No reported failure | No reported failure |
| Room temperature, days | No reported failure | Reported fine; shorter window |
| Room temperature, weeks | Reported fine | The room says do not |
| Warm transit, 30 °C+ | No failure logged, including several bad ones | One visible degradant peak on a chromatogram |
| Frozen once | Fine | Contested; no consensus in three years |
| Freeze–thaw cycled | Fine | The room says no |
| Direct sunlight, days | Keep it in the carton | Keep it in the carton |
Cold packs that arrive warm
A liquid gel pack tells you the parcel was above freezing. It does not tell you your vial cooked. Because the powder is robust, a warm transit on lyophilised material is very unlikely to matter — and members who tested after bad transits have consistently got clean results back. If you are genuinely worried, test it; that is what #test-results is for.
Seasonality, which is the actual risk
- Northern-hemisphere summer, June–August: heat. Hot mailboxes and un-air-conditioned depots. Two members have lost a cold pack entirely on an inland leg.
- Australian summer, December–February: the hardest test anybody gives a parcel. The channel's advice is to order in a cooler month if you have the choice.
- Canadian and northern-European winter, December–March: the risk inverts. Freezing, not cooking, and it gets discussed far less than it should.
- February generally: supplier lead times stretch around Chinese New Year, so parcels sit longer before they even start moving.
Travel
A small soft cooler with two frozen gel packs has held under 8 °C for eleven hours on a drive, by member measurement. For flying, hand luggage every time — the hold is not temperature controlled in the way people assume. Hotel minibars are frequently not cold enough, which is why at least one member travels with a thermometer, which is ridiculous and also correct.
Practical habits from the channel
- Back of the middle shelf. Never the door.
- A thermometer, and look at it occasionally.
- Concentration and date written on every vial in marker the moment you reconstitute it.
- Keep the carton. Light is a minor risk but the carton is free.
- A power cut with the door kept shut for a few hours is fine. A full fridge holds temperature surprisingly well.
- If the lyophilised cake is a puddle rather than a cake, something already happened to it before it reached you.