Does Lactose affect the Original Gravity Reading?

[thedrayman]

Had a great BrewDay yesterday making a firkins-worth of Milk Stout, flavoured with vanilla pods (which had been pre-soaking in Bacardi Oakheart), and cinammon.

At pitching the original gravity was 1058 and my question is...I know lactose is only partially-fermentable by yeast (leaving the required residual sweetness for a milk stout) but does its' addition also affect the gravity reading?

I usually list my beers with an OG however I was thinking that, in this case, I may have to do it by taking a start reading and finish reading, then work out the % abv to get an idea of the strength. Does that sound about right?

 

[orlando]

It will add gravity points so what you are suggesting will be necessary. I suggest you get some brewing software which will make the calculation of how much EACH fermentable you add raises the gravity, you can then adjust the amount you use accordingly. BeerSmith is what I use (free for 21 days) but GW's Beer Engine or Brewmate are decent enough free ones.