Is an SWB order from Chengdu likely to hold cold chain to Japan?

The specifics, since they change the answer: SWB · Chengdu · Japan.

This is a planning question. I know what my options are; I do not know how to weigh them.

What I want is the minimum viable version, which I suspect is smaller than what I would design.

What does a sensible plan look like, and what are the decision points?

Answer first: for a lyophilised solid the cold chain matters far less than people believe, and for a solution it matters far more than they act as though it does.

A pack that arrived hard tells you about the last day of transit only, since it will have melted and, if the ambient dropped, partially refrozen.

Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.

Phase-change pack hold time is a function of mass, latent heat and insulation, and published figures for small parcels are on the order of one to two days.

Lyophilised tolerates the lane. That is the answer for almost every order.

The honest answer is that the cold pack is doing much less than people think and that shipping lyophilised is what actually protects the material.

Arrhenius behaviour means the degradation rate roughly doubles per ten degrees. A week at thirty degrees is therefore a meaningful exposure for a solution and an immaterial one for a dry solid.

The underlying point is that a single-use temperature logger costs a few pounds, records the whole journey and converts an argument into a record. If the history matters, this is the answer.

The caveat is that a warm transit is survivable for a solid and materially different for a solution.

Solutions are a different question and deserve the worry the solids get.

edited 16 Apr 2026 by marta_okonkwo — added the placebo-arm figures

Start with the physical state, because it changes the answer completely and is the first thing to establish.

That is the argument for shipping lyophilised rather than for shipping colder. A dry powder with low residual moisture is stable at ambient for months; the pathways that matter need water.

Asking a supplier to hold a shipment during a heatwave is reasonable and the better ones agree; the cost is a week and the benefit is a shorter warm exposure for anything in solution.

A liquefied pack is expected. It is not evidence of a problem.

edited 16 Apr 2026 by sian_llewellyn — fixed an arithmetic slip in the third paragraph

If temperature history matters to you, buy a data logger. It is the only way to know.

A single phase-change pack in a thin-walled box holds below ten degrees for roughly one to two days at twenty-five degrees ambient, and under a day at thirty-five. On a nine-to-fourteen-day lane the material is at ambient for most of the journey whatever was packed with it.

Solid-state stability of lyophilised peptides at ambient temperature is documented in formulation studies with residual moisture as the dominant variable.

The domestic leg is the part you control. Refrigerate it promptly.

The short version: a spent cold pack on arrival is expected, the solid does not mind, and the pack was never going to last twelve days.

Once the parcel arrives, the domestic leg is the controllable part: get it into the refrigerator promptly rather than leaving it in a warm hallway for a day.

A cold pack tells you nothing about the eleven days before the last one.

Buy a logger if you actually want to know. Everything else is inference.