Yesterday, after feeding my starters (thanks again, Benny!), I left them away from (direct) sunlight for most of the day.
But with nothing actually covering or obscuring my sealed Weck jars.
In the late afternoon - probably about four hours later - I covered both jars with an opaque cloth.
Both starters then doubled in size.
This makes me wonder whether starters do better without any kind of light!
Or was it just that by the end of the day (during which room temperature had been almost constant, maybe even a little cooler later) more time had passed?
???
It's the time.
The growth is exponential, so at first there appears to be nothing happening, you might think that the microbes are dead, then suddenly you see life and as it grows it rate increases exponentially so if you don't watch it later on, just like with your dough, it may zoom past peak.
The whole "direct sunlight" thing makes no sense to me. You have two panes of glass that cut off most of the UV radiation, then another layer of glass in your jar. In addition to that, <UV> light can't penetrate starter for more than a few microns, meaning that only an infinitesmal portion of the starter can be affected.
Thanks, Ilya, Benny and suave - another variable to ignore and (so) make life easier :-)
Here's a good idea:
https://breadtopia.com/drying-sourdough-starter-for-long-term-storage/
There's also a link there to another page and video about how to revive a dried starter.
I did that and it worked surprisingly well. I had to spread it so thin I could see my Silpat through it (like tissue paper). After a year of being dehydrated my starter was able to come back to life. I've still got some dehydrated stuff left in my jar. I haven't tested it recently, going on almost two years now. It's probably about time though.
Thanks Dave and Sugarowl - I'd read about that in Raffa; great to know it really works!