Yeast Starter
 

If I make a Yeast Starter and don't want to dump all the liquid into the wort (diluting the good wort with crappy starter wort) and instead want to let the starter ferment for a few days, and decant off the liquid and pitch the remaining slurry/yeast - how much water - DME should I use for a 5 gallon brew?
1 cup - 2 liters, and decant? Will this make too much yeast?
1/2 cup to 1 liter?

Welcome to HBT!

What's your predicted OG? Ale or lager?

Use a ratio of 1:100, i.e. 100 grams per liter. I'd make a 1.5-2 liter starter. Less than that, and you don't get a whole lot of propagation.

How big a starter depends on the OG of your wort, if it's an ale or lager, and how old the yeast is. Use this calculator:

http://www.mrmalty.com/calc/calc.html

As for the ratio of water to DME, I always use 4 oz. of DME per liter - not sure what 4 oz. translates to in cups. This gives an SG of about 1.040.

The Mr Malty calculator is based (I think) on dumping the entire contents of the starter flask into the wort.
If you decant off the liquid and only pitch the slurry, you will have less yeast. Also - I think the calculator assumes 18 hours? What if its more or less?

Its probably not a big deal if Im off a bit, I would hate to over pitch yeast though, and not get a good flavor.

ArcaneXor, 100 grams per liter is a 1:10 ratio. (100g:1000mL).

4oz is 112 grams (28g per oz) so DeafSmith's recipe is also approximately 1:10.

So, a yeast starter added to the wort could effect the SG of the wort if the SG's are different. For an accurate OG reading, do you measure your OG after you pitch your yeast?