Saturday, 20 May 2017

08:58 – It was 59F (15C) when I took Colin out at about 0640 this morning, sunny and calm.┬áIt’s already up to 76F. We did have thunder and lightning yesterday afternoon and overnight, but only about 0.2″ (0.5cm) of rain.

We filled bottles yesterday, including 142 bottles of starch indicator solution for chemistry kits. That presents an interesting problem, because starch solution is an ideal growth medium for molds, and the polyethylene bottles can’t be autoclaved or they’ll melt. Boiling the solution kills all of the microorganisms in it, but it doesn’t kill mold spores. Once the bottled solution cools, the mold spores germinate. We do add a small amount of thymol to the solution, which helps but isn’t a complete solution.

So we use a process invented in the 19th century by a scientist named Tyndal. That process, called Tyndallization, involves submerging the bottles in boiling water to kill all the live microorganisms (but not the mold spores). We then allow the bottles to sit for several days at room temperature, whereupon any spores present germinate into live mold organisms. When all the spores have had a chance to germinate, we again submerge the bottles in boiling water to kill the new live mold.

Back when Tyndal developed his process, autoclaves and home-size pressure cookers weren’t yet available. Pressure canning was done, but only on a commercial scale. Tyndallization was the only option for home- or lab-scale autoclaving. Interestingly, that process is still used today as an alternative to pressure canning or autoclaving to sterilize materials that won’t stand up to the temperatures used for those modern processes.