Why I no longer keep my vials in the fridge door

The fridge door is the most convenient spot in the lab. Open, reach, done. For the same reason, everything small and often used ends up there. For years ours held spare batteries, a tube of glue and, in a cardboard box with no lid, the vials of lyophilised peptides.

I didn’t move them out of conviction. I moved them because of a thermometer.

A week with two thermometers

I had two thermometers with a minimum and maximum memory, bought for something else. One went on the door shelf, next to the box of vials. The other went on the middle shelf, towards the back. I left them there for an ordinary working week, with the fridge opened whenever anybody felt like it.

I won’t give the figures. They belong to my fridge, in one particular room, with my colleagues’ habits, and would say nothing about yours. I’ll only say what could be seen without a calculator. In the middle, the minimum and the maximum sat close together, well behaved, within the 2–8 °C I expect from a laboratory fridge. On the door, the gap between them was visibly wider, and the maximum had climbed higher than I would like to admit.

The explanation is mundane. When you open up, the door leaves the fridge with everything on it and spends a few dozen seconds in the air of the room. The middle shelf stays inside the cabinet, surrounded by cold things. A one-litre bottle doesn’t even notice the outing. A small vial, with a thin layer of dry powder at the bottom, has no mass with which to stand up to warm air and follows it almost at once. Multiply that by the number of openings in a working day, then by the days in a month.

Light, then water

The second problem I spotted without any instrument. The fridge bulb comes on at every opening, and whatever sits on the door also gets the room light, directly, for as long as somebody is looking for something else on the shelves. The vials are clear glass. Our box had no lid.

The general advice for lyophilised material is to keep it away from light, and I have no reason to be clever about it. For the principles I point to the PEPTIDÁE article on storing lyophilised compounds, written in Romanian, which takes them one by one. I was left with the practical side: an opaque box with a lid costs less than lunch.

The third is condensation. Every opening lets in warm, damp air, and the moisture settles on whatever is coldest and closest to hand. On the door, that means the vials. The stopper and the cap are there precisely so that the powder stays dry. The label, on the other hand, has no stopper.

I had two vials on which the batch number had softened into a grey smudge. The contents were, perhaps, fine. “Perhaps” is not a word I can enter in the logbook, so the two came off the records, with a shamefaced note in the margin. In the notebook, the page reads:

14 March. Batch illegible on two vials from the door. Taken out of use. Move EVERYTHING off the door by Friday.

Where they are now

In the fridge

On the middle shelf, towards the back, but not touching the rear wall. In our fridge that wall ices up and then drips, so right against it is the second-worst address after the door. The vials sit in an opaque plastic box with a lid that clicks shut, alongside a sachet of silica gel that I replace when it changes colour. The lid says what is inside, so that nobody opens the box just to find out.

One of the thermometers has stayed there too, stuck to the box. I read it on Monday mornings, enter the minimum and the maximum in the notebook and reset it.

In the freezer

Same logic, with one extra degree of stubbornness. Nothing on the door, nothing in the front row, closed boxes. Ours is a manual-defrost freezer. That means ice to scrape off twice a year and a lost afternoon, but also a boring temperature, without the short warming cycles that self-defrosting models go through. Boring is exactly what I want from −20 °C.

Which of the two

Fridge or freezer is not something I settle by guesswork. For each product I look at its own sheet, such as the GLOW BLEND product page, and at the papers that came with the batch. If I find nothing there, I look through the supplier’s frequently asked questions and only then write an email. I copy the answer into the logbook, next to the batch, with the date I received it. A colleague told me I was overdoing it. The same colleague asked me, two months later, where it says how a certain vial should be kept, and I handed over the notebook.

What ended up on the door

The shelf didn’t stay empty. Lab nature abhors a vacuum. It now holds the batteries, the tube of glue and a box of marker pens that somebody wants cold for a reason never explained. Things that don’t care how often we open the door.

On the inside of the door I stuck a strip of paper that says, in my handwriting: “Nothing with a batch number lives here”. The new colleague asked whether it was a joke. I showed him the page from 14 March.