Contamination at day nine: what went wrong

Six bags of grain spawn, inoculated on a Sunday, kept at a steady 24 degrees in a closet with a small heater and a thermometer I trust. By day six all of them showed clean white growth at the injection points. By day nine two of them had a green patch the size of a coin, and by day eleven those two were compost.

I kept a temperature log every twelve hours and it never moved more than a degree. So it was not the environment. I went back through the photos and the answer was in the first one: the bags I lost were the last two I inoculated, after I had already been at it for twenty minutes with the flow hood running and my sleeves rolled up.

The three things I would change. First, wipe the needle between every bag, not every three. Second, do not roll your sleeves up; the forearm is closer to the sterile field than you think. Third, and this is the one that actually cost me, do not take a phone call in the middle of a session. I picked it up, put it down, and went straight back to the next bag.

Four bags colonised fully and are in tubs now. I am posting the two failures because the four successes taught me nothing. Sterile technique is most of the job, and the job is mostly not getting bored.