What would be the purpose in adding dry hops, then removing them prior to adding a second, even third addition, rather than simply putting all the dry hops in at the same time?
If the answer has to do with wanting a stronger contribution from one variety of hops, please explain why that would be different from lowering or increasing hop quantity.
There is nothing to be gained from that practice, really. I can't imagine why anyone would go to the hassle of doing that.
A lot of brewers that make excellent dry-hopped beers have a limit to how many days they leave their beers on the dry hops. For example, this presentation on IIPA's by home brewer Nathan Smith (PDF), says that Firestone Walker only uses dry hops for 5 days, and Smith suggests a maximum contact time of 7 days. And Smith summarizes the purpose of multiple small dry-hop additions as giving the beer "bigger, longer-lasting aroma".
The thing to keep in mind here is that these brewers are using conicals and can pull the hops out of the beer using the bottom valve in the conical, preventing oxidation problems. If you're not using a conical, it's going to be a bit trickier to do multiple small dry-hop additions and avoid oxidation. My approach would be to dry hop in a keg. Store the dry hops in hop bags and suspend the bags from the lid using fishing line or something similar. Fill the keg headspace with CO2, leave the hops in the beer for 5-7 days, pull the bag and then repeat the process as many times as you like.
Will it make a big difference vs. just doing one hop addition? That's for you to decide, it's your beer. Try it both ways and see what you prefer.
Okay, here's the deal: I believe that time is the predominant factor in dry hopping, and I had previously thought quantity was just as important.
I did an IPA with Rye, double dry hopping, divided into:
Though I did not expect a difference, and with the help of a friend who is very good at distinguishing differences, we determined the first batch was significantly more aromatic. This is somewhat noticeable in the smell, but also very pronounced in your sinuses, a great addition to a beer I'm now quite proud of.
This seems to validate that a significant amount of your aroma comes from time in contact with hops, more so than quantity of the hops. Therefore, I would guess multiple additions is the best way to get the most aroma, once you're worried about leaving the hops in longer than x days (many people differ on how long it takes to get unpleasant taste from too much time in contact with hops).
Vinnie Cilurzo does (did) it, for whatever that's worth. From that article, it sounds as though the point is to keep a "big", fresh hop aroma, while removing most of the "bits" before they can contribute significant off flavors/aromas.
I haven't heard of anyone actually doing this, but I imagine the rationale is that dry hopping for longer than 5 days or so can lead to "stemmy" or grassy flavors. I guess if you were trying to go way overboard on the dry hopping you could get a little extra aroma without the stemmy/grassy flavors.
That said, no need to do this. Using the appropriate amount of dry hops just once should always do the trick.
As far as I understand, leaving hops in for a short time gives aroma, a medium time gives fruit and a long time gives vegetal/grass flavours.
When high quality jasmine tea is made, fresh flowers are mixed with the tea and left for a day, before being extracted and more fresh flowers added. This process is repeated several times.
