HeraldOfChange said:
Its frustrating searching for answers that are spread all over the place that turn out to be non-answers to a question that is now, 3 years old.
The level of knowledge available to homebrewers continues to advance. If you, or anyone else learns something about using new products, then by all means, share it. I'll be the first to applaud your effort. If you're not finding a succinct answer, then it's reasonable to think that there might not be one, yet. What you've learned would be a welcome addition to the knowledge pool.
I'm using Brewferm Isomerised Hop Extract 6%
*emphasis added*
The OP and my answer were dealing with CO2 hop extract, which is
not isomerized and contains hop oils, too. With those products, the creation of isomers (therefore IBUs) follows the normal bittering calculations.
With isomerized extract, all bets are off. The second you add them, is the second you have all those IBUs and the only thing you can do is lose them in the process. It's a straight ml/l ratio of bitterness added. It's as simple a volume ratio as possible. No amount of boiling fully isomerized products will add a single IBU. So, the best time to add isomerized extract is just before bottling, so that none are lost in the process.
It's fascinating to me how much homebrewers rail against big beer, but are quick to adopt their advanced "brewing" techniques. Isomerized extract is used in Miller beer, after filtration. It's been their method since the '60's. ...Just my opinion, but when a brewer looks for that level of precision, it's not brewing. It's engineering a barley beverage.
I am also using their, "Hoppy" Aroma Hop Oil. There are now, available to the Home Brewer, many such products which really ought to be part of the BeerSmith Recipe Calculator OR at least addable as an Extract Hop Ingredient.
Oil extracts are in the realm of brewer preference. There isn't a calculation associated with their use.
Again, this is part of the learning curve in homebrewing. I don't have a complete list of these products, do you? Please post it, if you do. It's the BeerSmith community that creates the lists that end up in the add-ons. Hops, yeasts and grains have all been updated over the last few years, from the efforts of individuals, like yourself.
****edit****
This website:
http://www.homebrewwest.ie/hop-extract-isomerised-6-100-ml-1568-p.asp
This seems to be the product HeraldOfChange is discussing. It has a few dosing ratios that can be used as a guideline.