Taking S.G. before topping up.

[shadow47]

Hi I'm making two wines and would like to take a hydrometer reading before brewing but need to leave a little head space then top up with water etc. later on.

Two methods I can think of;

A) Take hydrometer reading and quantity of liquid before topping up and doing the same with the stuff I'm topping up with and adding it up somehow (dunno how to do this yet, but I'm sure there's a way).

B) Topping it up before pitching, take reading then pour some of it into a wine bottle and keep it in the fridge until topping up.

Which would be best? And are there any other methods for doing this?

Thanks

 

[wurzel]

A: Make up to 7 pints (for a gall batch) take an SG reading and divide it by 8 and then multiply it by 7.

B: Pitch the yeast and put some into a bottle (no need to keep in the fridge) plug with cotton wool or what ever and add later