14:53 – Barbara has started her annual Deep Clean. She spent most of the morning in my office, and has declared herself satisfied with all but my main desk, which I haven’t even started on. Actually, I still have some work to do on my secondary (microscope) desk as well. My workroom is a disaster area, but I had to get my office organized and cleaned up first so that I’d have somewhere to use as a staging area while I cleaned up the workroom.

While I was cleaning off the microscope desk, it occurred to me that I probably still had everything there that I’d used to shoot the cover image for Illustrated Guide to Home Biology Experiments. Sure enough, I did. Not just the microscope itself, but the slides, coverslips, 96-well plate, 20-microliter minipipette, tubes, rack, and so on. And the bottles of 3% hydrogen peroxide and 70% isopropanol. Well, not the original bottles, but ones just like them.

And it occurred to me that we never mentioned in the book what that bottle of hydrogen peroxide was for. Drugstore (3%) hydrogen peroxide is death on microorganisms. Not just bacteria, but fungi, protists, viruses, many spores, and even prions. Of course, there are many other solutions that are good at killing microorganisms. The nice things about 3% hydrogen peroxide are that it presents no serious handling hazards and that it’s fugitive. That is, it quickly breaks down into ordinary water and oxygen gas, leaving no residue that might kill organisms that you’re trying to culture. It’s not as effective as autoclaving, but nearly so, and it can be used to sterilize materials that can’t be autoclaved. For those reasons, 30% hydrogen peroxide is commonly used as a stock solution to prepare dilute solutions to sterlize commercial food preparation equipment, which means it’s cheap and readily available locally.