I've just bought this stuff (pictured) - what appears to be Irish moss in its natural, dried state.

Being a bit of a noob I haven't used Irish moss before, thinking (perhaps foolishly) that my beers could be clear with it. Nope... at least, not so far. So, I bought this particular product for a couple of reasons...

  1. For various personal reasons I like to keep my beers as "natural" as possible - I'd rather not start adding pig bones, fish bits, or lab-produced carrageenan. Call me weird, but I'd rather avoid anything that comes in those little white snap-top pots with unclear labelling. So, if I'm going to start using some kind of clearing agent I'd rather be using something that is as natural as possible... hence this choice of product over normal pre-prepared Irish moss.
  2. This product cost only £10 for 250g, which is at least 50% cheaper than buying it in pots.

My question is, simply and noobishly, how best do I use this? Perhaps more specifically...

  • Generically, how much do I use? Currently I'm doing 5 gallon batches.
  • Do I put it in the last 15 minutes of the boil?
  • Do I put it in as it is, or do I grind it to a powder to increase its surface area contact?
  • Do I need to rehydrate it first?
  • Anything else I should know?

Ta very much!

Irish Moss

2 Answers 2


The flakes look a little large (this may or may not be a matter of perspective), but past that, I'd say it's perfectly fine to use. Add one teaspoon per 5-gallon batch at the last 15 minutes. Before adding it, I would suggest crushing it down just a bit further, either via a rolling pin, chopping, or using a coffee grinder (specifically re-purposed for stuff other than grinding coffee beans). You don't need to grind it down to a powder, but it should be in smaller flakes to allow for the widest dispersion among your boil and ensure the most amount of surface area to get in contact with the wort.

That said, if you're going for clarity without any bizarre additives, and you can force carbonate your beer, you may want to look into filtering your beer.

  • Rehydrate the Irish moss in 1/2 cup of warm water for 30 minutes before adding to the boil. Should make it slightly more effective. Commented Jan 23, 2014 at 15:10
  • Cool, thanks. Pretty much confirms what I thought anyway :-) I'll be grinding it down, rehydrating it, and adding it to the boil for 15 minutes.
    – Doug
    Commented Jan 23, 2014 at 15:59
  • My personal experience is that there is nothing to be gained by crushing the IM before use.
    – Denny Conn
    Commented Jan 23, 2014 at 16:11
  • 1
    Irish moss is a bizarre additive?
    – Denny Conn
    Commented Jan 23, 2014 at 23:13
  • I intended that to refer to the various post-boil finings he mentioned his his reluctance towards using, e.g. Gelatin, Polyclar, Isinglass, etc.
    – Scott
    Commented Jan 24, 2014 at 0:26

If you brew extract, use 1/4 tsp. 15 min. before the end of the boil. If you brew all grain, use 1 tsp. for 15 min. Rehydration is not essential, but it will make it a bit more effective.

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