It’s quite cold in Canberra at the moment - internal house temperature is 12-14 degrees when our heating isn’t on - so I have been using a garden heat mat underneath the glass jar of embryonic levain. Does anyone have any advice on whether this technique, if I can call it that, has any obvious cons? So far, day four, using Ken Forkish’s levain recipe the levain seems relatively lively but…
While a garden heat mat can add warmth to your levain, it may not provide precise temperature control. Maintaining a consistent and specific temperature is crucial for fermentation, and if the mat gets too hot or too cold, it could affect the activity of the microorganisms in your levain.
Some garden heat mats can get quite warm, and overheating your levain could kill off the beneficial microorganisms. It’s essential to monitor the temperature closely and avoid exposing the levain to extreme heat.
The seedling starter mats I have (in the $15 range) do not have temp control, measure 10x20 inches, and bumps the soil temp in a std 1020 nursery tray only 10°F, just enough to get seeds germinated in an unheated room. In a heated room it gets too hot, will kill the seeds. I would be concerned about the microbes in the starter in the bottom of the dish, closest to the heat mat. Maybe put a thick towel between the mat and the starter dish. (I put a towel between the heat mat and the seed trays, anyway.)
Fwiw, tossing an 11 or 15 watt incandescent light bulb into a cardboard box with your starter is an option. I have proof the dough for many bakes this way. You could put your heat mat inside a cardboard box and use it to heat the environment inside of the box, keeping the starter well away from the mat.