According to BYO malt absorbs roughly 1.04L of water per kg malt. Knowing this makes calculating things like mash and sparge water quite a bit easier.
Is there a rough absorption rate for hops?
I've searched round the web but cannot seem to find anything. I guess it may vary according to the hop size and density, but some rough figures will help with calculations like topping up water and rackable post-fermentation volume.
Is there a difference between adding hops in the boil vs dry hop?
I use an Italian made brew calculator, Calcoliamo Birra, app that calculates hops water absorption at 0.12 qt/oz which is about half a cup per ounce.
Update: Last night I made a hop tea to increase the bitterness in a pilsner I wasn't satisfied with. I decided to collect some data for hops liquid absorption while I was at it. I boiled one ounce of Saaz pellets in a quart of water for 15 min, then pours the contents through a strainer lined with cheese cloth to filter the hops particles. I then let it sit until no more liquid was dripping. I then transferred the hops to a graduated measuring cup. The final volume was right at 1 cup maybe a little under. The 1 ounce of Saaz took up about a quarter of a cup, preboil. The hops absorbed approximately 3/4 of a cup of liquid in the 15 min boil.
Beer-N-BBQ by Larry says hops absorb 0,0033L of wort per gram. I don't know where the value actually comes from though.
