There are several options to cleaning your whiskey barrel. In this process, you are looking to get rid of anything that would contaminate your beer. Remember, a barrel is the same thing as a secondary fermentor. Below I have outlined several options and provided your with the option that we went with and why.
Sanitize like a fermentor
You can put a typical no rinse sanitizer into a barrel like what you would do with a fermentor and let it sit for awhile. This will kill most things on the surface of the barrel and if your leave it sit for long enough, it will absorb into the wood killing things that are deeper. It will not get rid of anything, nor will any of these methods. I considered this for a long time, but decided against it as I didn’t want anything left that would kill any yeast that transferred over. We are looking to bottle this beer after aging so I want to have some yeast alive for carbonating the bottles.
Campden tablets are usually used in wine making. They kill pretty much everything that they come in contact with. For the reasons noted above we did not go this route, but may in the future.
Potassium Metabisulfite Powder
This is the active ingredient in campden tablets and I did not pick it for the same reasons.
I decided to go with hot water. I heated 15 gallons of water up to 170 degrees and then poured it into the barrel with the help of a funnel. I then sealed the barrel up and left it sit there for 30 minutes. I was looking to neutralize anything on the surface and to also check for leaks. The hot water allows the wood to swell quickly, ensuring that any leak would be plugged more quickly. I also knew that we had a good barrel that was sealed well. In addition, the beer going into the barrel is currently at 9.5% ABV, so most critters that would like to ruin our beer wouldn’t be able to survive in that setting.