I have a Oatmeal Stout recipe that calls for 4 tsp/ 1 gram of Irish moss powder. The LHBS had Irish moss, but I wouldn't call it a powder. They're small flat pieces maybe the size of half a grain of rice. Should I pulverize it in a morter and pestle? I would assume this would make it more efficient. Or just measure out a 1 gram and not worry.

If I use my (near impossible to sterilize) morter and pestle, is there any concern that the irish moss would not be sterile? Its going in the last 10 minutes of the boil.


3 Answers 3


Just add 1/4 tsp or 1g of what you have. Irish moss is a fining - it helps draw together proteins in the boil, and is primarily added to improve clarity, but it can also provide a finer head. It's not critical how much you use - some brewers use 1/4 tsp per 5 gallons, others 1 tsp.

The moss doesn't have to be sterile - anything added to the boil is quickly sanitized since most organisms cannot survive the heat. I would just make sure the pestle and mortar is clean - I use mine for crushing curry spices, and I wouldn't any hint of that in a beer!


Well if the recipe calls for a gram it shouldn't matter if its a powder or flakes, a gram is a gram. Irish moss is normally that flakey stuff you describe so I would just go with it either way as 4tsp or a gram. For what its worth, its not going to make a difference in a big dark Oatmeal Stout.


regular and powder are not the same. with powder you use way less than with regular.

  • While potentially helpful, this post is not responsive to the question, and should have been made as a comment. Commented Aug 5, 2014 at 16:16

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