I read recently, unfortunately I did not record the web address, of a technique for progressive building of a starter/levain whilst changing the hydration progressively, if required. The idea is that you don't shock your beasties by a 'sudden' change in hydration, the growth of the population is controlled and invigorated by the regular feedings and there is not an excessive volume to be populated at any one time or that cannot be used by the population.
The technique was to start with a small amout of your culture and to increase the mass in three stages (0,8 and 16 hours) so that after 24hrs you had the required mass and hydration of starter/levain that would be alive and kicking the proverbial six pointers.
The link that follows points to a spreadsheet that you can down-load that does the calculations for this method for you.
Data entry is in the top half of the area and includes your target hydration, target mass, a buffer mass (to allow for errors/losses) and the hydration of your starting culture. Using TAB between entries jumps to the next data entry cell.
The results appear in the bottom half in the grey cells. The intermediate hydration figures are for information only.
I hope this proves useful. Any ideas for other 'calculators' or improvements to this one, feel free to contribute.