A five gallon Maibock at 1.068 requires roughly 469 billion cells. Therefore a 9 Liter starter using 1 vial will suffice. I recommend making 9L of starter wort at a gravity of 1.030. (27oz DME). Boil the starter wort with 1/2 tsp yeast nutrient for 10-15min then chill down into the 60’s, aerate the wort and pitch one vial of Bock yeast. Ferment in the 60’s to terminal gravity and crash cool. On brew day decant the beer and pitch the slurry into your well aerated/oxygenated Maibock wort at lager pitching temps (45-50F).
Thanks! Could I put the 9L starter in a 5-gallon glass carboy?
Yes.
Great! And how many days do you think it will take for the starter to be ready to pitch?
Depends on the condition of the yeast, yeast strain and the fermentation temp, but I would expect it to take about 5-7 days to ferment out at 60F.
fun fact.
I to was using 100gr DME per litre until I checked the gravity one day. At the end of 15min boil I had around 800ml of starter wort at 1.056 SG. I had never taken the boil into account. I now add in the 15min boil off volume (200ml) to my staters. I use 100 grams of DME for a 1200ml starter @ 15min and end up with 1000ml vol at ~1.037 SG.