Planning on brewing a 10.5 gallon RIS with an OG of 1.100. According to Mr. Malty, I need two smack packs and a 5.5 liter starter with my stir plate.
My first starter was 1.6 liters with one smack pack. I then decanted and poured half the yeast into a 1 gallon jar and added a liter starter (no stir plate). I then added another 1.6 liters to my flask that will be placed on the stir plate.
Will this give me enough yeast for 10.5 gallons at 1.100 OG?
When building up a starter I find it easier to think in terms of Billions of cells, especially when converting from one smack pack to two, or when using a slurry. There are two main limitation to yeast growth: fermentable material and oxygen. On a stir plate, or with intermittent shaking there is plenty of oxygen leaving just fermentable material as a limiting factor.
1 smack pack is 100 Billion cells
each litter (of 1.035 wort) will support 100 Billion cells
You need 700 billion cells.
to support 700 billion cells you need a volume of 7 litters. Because you don’t have that you probably don’t have enough cells. If I were you I would pitch the yeast you have into 2 gallons of your second running and then the next day dump the rest on top of it.
yeastcalc.com is great to help figure out these stepped starters.
If you repeat your 2nd step with another combined 2.6L you will have enough yeast.
I usually make a “5 gallon starter” of regular strength beer as a starter for a big beer.
[quote=“TG”]
I usually make a “5 gallon starter” of regular strength beer as a starter for a big beer.[/quote]
This what I usually do also. However I didn’t want to wait the two weeks for the first batch to finish.
Looks like by the time I end up with all the “step ups”. I could have brewed a batch 
Roddy, that is why most homebrewers will just make a batch and use the yeast. It can get wasteful (not to mention pricey) to keep stepping up starters.
I have about 12 mason jars full of yeast in the fridge. Unfortunately no Wyeast 1028.
Me too. Grosses people out when they reach in to get a beer. Makes me smile when I get one. 
