A freezer map, or how I find any vial in thirty seconds

One Tuesday in February I stood with the freezer door open for four minutes. I know it was four because the alarm went off, and ours is an alarm that takes its time. I was looking for a vial of lyophilised peptide from a batch that had arrived three weeks earlier, and I was certain I had put it “in the blue box, at the top”. There were three blue boxes. “At the top” was a matter of opinion.

I found it in the end, in a zip-lock bag underneath a box of pipette tips that had no business being there. That evening I wrote a single line in my notebook, in capitals: THE FREEZER IS NOT A DRAWER. Two afternoons of moving, labelling and writing followed, and since then I can pull out any vial in under half a minute. I timed it. That is the sort of person I am.

First, the bags went in the bin

Bags slide over one another, freeze together and hide whatever is inside them. I replaced them with cardboard freezer boxes, the kind with a divider grid, in the wide-cell version, five by five, where a capped glass vial drops in without being forced. For the taller vials I have two plastic boxes with clear lids, inherited from a colleague who moved to another city and left behind more boxes than explanations.

Each box has one job. It holds a single compound or, when I only have a few vials, compounds from the same area of work. The rule that has spared me the most muddles is a smaller one: different batches never share a row. One row, one batch. If there are cells left over, they stay empty, however much my fingers itch to “use the space”.

I write the box code twice, on the lid and on the side that faces me when I pull the drawer out. The side matters more. The boxes are stacked, and nobody sees the lid of the bottom one without lifting everything above it, which is exactly the move I am trying to avoid.

The map on the door

Our freezer has four drawers. I named them A, B, C and D, top to bottom. Each takes four stacks of boxes, numbered left to right, and within a stack the boxes are counted from the bottom. So a box has an address along the lines of C2-1. The vial also gets its row and its cell in the grid: C2-1, row b, cell 4. It sounds bureaucratic. It takes two seconds to read.

The map is a sheet of A4 in a plastic sleeve, held to the outside of the door by two magnets. The outside, because I want to read it before I open up, not with cold air pouring over my feet. I keep it up to date in pencil. At the start I had a printed table, a handsome one, with borders. It was true for about two weeks, after which it became literature.

Drawer A is for what I take out often, D for reserves. I don’t cram the boxes in; I leave two fingers of clearance above each stack, so the drawer shuts without crushing a lid. The freezer sits at −20 °C. If a particular product calls for something else, its data sheet says so, and I read the data sheet before I pick a drawer for it, not after.

What goes on the vial and what goes in the notebook

The manufacturer’s label stays untouched. I stick nothing over it and write nothing on it. Mine is a small round one on the cap, from a roll of labels made for freezers. Office labels last until the first frost, and then you find them at the bottom of the box, face down, naturally. A dot on a cap doesn’t hold much: the address and the date the vial came in. The name and the batch are already on the factory label, and that is where I look for them.

I did try coloured dots, one colour for each area of work. A month later nobody knew what green meant. I kept just one. A red dot says this is the last vial of its batch.

Everything else lives in the logbook, the dull part that gets me out of trouble. I have a notebook with numbered pages, kept on the shelf next to the freezer, and a spreadsheet on the computer with the same columns: compound, batch, date in, address, date out, who took it. The notebook is for the moment when I’m wearing gloves and holding a vial. The spreadsheet is for searching.

I copy the compound name exactly as the supplier writes it, with no abbreviations dreamt up by me at five o’clock. If the label says SEMAX, my records don’t say “Sx”. When I’m unsure of a name, I open the PEPTIDÁE catalogue of research peptides and take it from there letter by letter. The site is in Romanian, but a compound name is a compound name. The batch number I transcribe from the vial. Not from memory and not from the invoice.

Two rules hold the whole thing up. No vial leaves its box without a line being written. And its cell stays empty afterwards: I don’t move another vial in to make things look tidy, because the old address would start telling lies. I understood better why I care so much about the batch number after reading an article on batch traceability for research peptides on the same supplier’s blog. In short, a result without a batch is a story, not a measurement.

The Friday test

Once a month, on a Friday, a colleague puts a finger on a random line of the spreadsheet and reads me the compound and the batch. The stopwatch starts on the last word, not when the door opens. I read the address off the map, open up, pull the drawer, lift out the box, take the vial and compare the batch on the label with the one I was given. It usually comes in at twenty-something seconds, with the door open for about ten of them. The alarm hasn’t had the chance to go off since February.

When it goes wrong, the paper is almost always to blame. Somebody moved a box and never rubbed out the pencil, or wrote an address out of habit, without looking. Last month I failed the test myself. The vial was sitting quietly in its place, but I had read the address from an old map, forgotten in the desk drawer. I tore it into four and wrote, in the corner of the good one, the date of the last change.