Starter use and maintenance
I'm moving some questions from this topic over here so I don't hijack that one.
My questions came after reading Doc.Dough's following posts:
1:1:1 and 12 hrs at 30°C will initially have a relatively high acidity when you refresh, and thus when you feed it you need to add enough flour and water to partially neutralize the acid and get the post-refresh pH above about 5 (>6 is better). Not doing so sets you up for the LAB to stop replicating (at about pH3.5) before they have replaced the initial population and the LAB population density goes down a little bit with each refresh which produces less acid for the next round. If you do this for very long, you lose enough of the LAB that you don't have enough to initiate a batch of sourdough. Mini Oven has coached more people than I can count about feeding at 5:10:15 to recover a failing starter, and I subscribe to that practice for recovery even though I advocate feeding at a ratio of at least 1:x:x where 2<x<20 [minimum 2 for the reason stated; maximum 20 to assure that you suppress the potential contaminants in your flour - which is not sterile]. Just my $0.02 worth.
I use a weather/seasonally adjusted X:13:15 refresh ratio where X=6 in the winter and as low as 1 in the heat of the summer (to the extent that SoCal has summer heat). Though lately I have been using a thermostatically controlled water bath at 29°C and X=~4 to get a very predictable 12hrs to the point where it has lost 2% of the weight of the added flour (which if the numbers are in grams turns out to be about 300mg). The weight loss is observing the CO2 lost to fermentation and is always approximate just because I have to thump it to get it to degas before I weigh it. Time to reach that point is a better gauge of activity than volume increase and also works across all hydration levels while giving an excellent basis for comparing multiple starters refreshed in parallel. The method was developed to measure the maturity of levain that was being mixed at 230% hydration where it does not increase in volume and bubble activity doesn't work either.
Interesting. I haven't seen weight loss used as a measurement of activity before. How does the 2% loss line up with volume change for a 100%-ish hydration starter? Do you observe that it reaches that point before or after peak? Will water evaporation also play an effect in this? Won't the water in a just-fed starter start to evaporate and the starter lose some weight because of it during 12 hours? Being flour weight, that means if you mix a starter with 30g seed, 100g flour and 100g water, you want to use it in a dough when it has lost 2g of the flour, which would be when the total mix weigh 228g?
Could you stir the starter before weighing to get more of the gas out and a more accurate reading? Of course adding the spoon or spatula to the weight since it will have some of the starter stick to it after stirring.
What's the reason you use 29C and not something like 25-26 which I've seen many times hailed as an ideal temperature for starters?