[rbowers]

I brewed a hoppy American amber that I dry hopped with 3oz of hops (Amarillo, Simcoe, centennial) and after about two weeks the hop flavor and aroma is very muted from what it was before.  Numerous potential reasons (O2 getting in when dropping the hops in and removing, despite fluishing with CO2, I suspect may have had a role).  Read about filling the keg with starsan and pushing it out with CO2 as a way to minimize O2 prior to racking which I can do the next time.  But for this beer- is there anything that can be done to brighten it back up?  Drop another few ounces of hops in to dry hop a second time?  May just leave them in if I did that as well as do that in the future.  Seems like my hoppy beers just fade so quickly.

[MNWayne]

When I dry hop it's always in the keg and I leave them in (in a bag) until it kicks.

[Robert]

If I dry hop, I do it in the fermenter while there's still a bit of active fermentation to go, so yeast can scavenge any oxygen introduced,  then do a closed transfer to a liquid-purged keg.  Ideally I don't dry hop, so there's no oxygen exposure after pitching and aeration up until it hits the glass.  As for the current batch, I'd worry opening it up to add more hops might just start the cycle again.  Oxygen is a b*****, and dry hop character is fleeting.  Best plan is always to drink dry hopped beers fast and enjoy it while it lasts.

[majorvices]

Yep you probably nailed it. Oxidation is one of the biggest causes of hop flavor and aroma loss. If it is in trghe keg throw some more hops in there!

[rbowers]

So on the idea of limiting oxygen: if I want to dry hop in the keg is it worth putting the hops in a bag into the keg, filling with star san and quickly pushing the star san out with CO2 then racking the beer into the keg?  These will probably be pellet hops in a fine mesh bag with some type of weight.  Not sure how much hop aroma you lose to the quick starsan contact with the beer- hopefully not much.  This would prevent any oxygen from getting in but potentially at a cost.  Not sure if that is a better solution than just filling up the keg as much as possible with the beer, drop the dry hops in, and flush as much as possible.

[jeffy]

So on the idea of limiting oxygen: if I want to dry hop in the keg is it worth putting the hops in a bag into the keg, filling with star san and quickly pushing the star san out with CO2 then racking the beer into the keg?  These will probably be pellet hops in a fine mesh bag with some type of weight.  Not sure how much hop aroma you lose to the quick starsan contact with the beer- hopefully not much.  This would prevent any oxygen from getting in but potentially at a cost.  Not sure if that is a better solution than just filling up the keg as much as possible with the beer, drop the dry hops in, and flush as much as possible.

I think once you have the sanitizer pushed out of the keg you could either add the hops when empty or add the beer and then add the hops.  If you are intent on dry hopping this may be the best method.
The last one I did, I added the hops to the beer as it was finishing fermentation like Robert said below, then purged the kegs and transferred.

[denny]

When I dry hop it's always in the keg and I leave them in (in a bag) until it kicks.

Same here