Something that every hop head wants to do is to load a beer up with hops. Dry hopping is basically an attempt by brewers to spike their brews with fresh hop aroma and, to a lesser extent, flavor. Cask ales are a favorite target for the pros to drop a cheese cloth full of fresh hops into a cask prior to sealing it with a bong. Other breweries will age an IPA in a bright tank for a period of time, on a bed of hops. These techniques work well on the home brewer scale as well, and there are plenty of simple techniques about which much has been written that can be used and found in multiple sources. The idea here is to extract the hop oils from the hops, not the bitter acids as the oils are generally lost during the boil. The more oils in the hops the less hops needed for dry hopping. See the hop oil chart for an idea of what the oil content (percent) is for many US hops. I will add others as I find them.
Anyone can take a bunch of hops, throw them into a carboy, and rack a beer onto said hops. Simple. But what are the pitfalls? Firstly, the hops added to the secondary will take up volume, so beer will be lost. This may not be desireable in a 5 gallon batch. Secondly, I would like to tell a little story about a dry hop infection. Back in the day of Ramapo Valley Brewpub, Neill Acer came up with an idea that we have a club homebrew competition where each brewer would buy 5 gallons of his wort and make a beer with it, whatever we wanted. At a certain date, a panel of judges would decide the winner, and prizes would be given to best...and worst....brews. The judges would include Neill, and Greg Zacardi of Ramstein fame (the poor guy had no idea what he was getting into).
In any event, we (me and Mike) decided to do a small mash and increase the gravity, making a dry hopped red ale of decent strength. The hops were fresh and home-grown (coincidently by my friend Roger who was also present for judging). So off we went, doing a partial mash with a few pounds of Munich, adding the collected wort to the existing wort, and then adding hops and doing a full 90 minute boil. Pitched our yeast and a couple of weeks later, the beer tasted good on the transfer into the secondary where we added several ounces of fresh grown hops. We allowed this to sit for a period of time then bottled. Whoa, this brew tasted funny! I knew immediately that things had gone horribly wrong. Oh well...what could have been a great beer...
On competition day, we all presented out brews to the judges. All were disasters. One bad one after another. Ours was among the worst as the infection was really taking hold.
The lesson: Neill told me that he always sanitizes hops before dry hopping. Whatever technique you want to use, protect your work! In a big brewery, screwing up costs big bucks. On the homebrew scale, not so bad, but all that time and effort is wasted.
That said, hops generally can be used on finished beer and not be a problem, but then there is always a slight risk.
What to do if you cannot risk contamination?
Firstly, sanitize. Hops can be santized easily with vodka and added that way if desired. A hop tea is another technique. 170F is all that is needed for sanitization, just hold that temperature for 10 minutes.
Second issue is beer loss, which I for one cannot tolerate! Cheesecloth works, but its tough getting one in and especially out of a carboy. Simple solution would be to have a dry-hop secondary bucket for this purpose, so as to eliminate the carboy nightmare. I don't like using plastic but for an occasional special brew, it can be advantageous to have a lidded bucket.
My latest and immensly successful technique is:
For those of you that are reading this and would like to save time (which from what I have seen most of you do) this method rules!