Barrel Rehab 101

>> Tuesday, June 30, 2020

For today's write-up, I decided to document my process for rehabbing oak barrels. The primary issue I'm trying to solve here is re-hydrating a dry barrel. When barrels sit dry, the oak literally shrinks allowing small gaps to form between the staves. The result is the barrel is no longer water-tight. 

I have used this process on two 30 gallon barrels that sat dry for a little over a year. If you've sunk some cash into a barrel and aren't quite ready to turn it into a planter or use it for smoking wood, this process might help you out.

The TLDR version is the rehab process involves multiple steaming sessions, possibly tightening the hoops, and the French method of re-hydrating. The goal is to slowly swell the wood with steam until it's water-tight or close to it. Then, finish it off with the French Method before filling with beer.

First off, a couple assumptions. Your barrel needs to be in somewhat decent shape. So preferably no broken/cracked staves, no mold, no extreme warping, and hopefully it's still intact (versus a pile of hoops and staves). If your barrel meets that criteria, read on. Also worth noting, this process will reduce the spirit character in your barrel, moving it closer to being a neutral barrel. Each steaming session and fill is going to extract some of the wood and spirit character. If you're planning on doing a bourbon barrel stout, you may need to season the barrel before filling. If you're doing a sour beer, that's probably not a major concern.

One more thing, if you've never been to Utah, most of the state has very low humidity. Annually, the humidity is rarely higher than ~15% unless it's right after a rainstorm. According to my Nest thermostat, the inside humidity is usually right around 30%; that's with a humidifier running during the winter and a dozen-ish  houseplants. Generally speaking, the lower the relative humidity, the faster an empty barrel will dry out. 

Special Equipment
  • Barrel steamer - I highly recommend one of these for anyone that uses barrels and/or brews sour beers. Wallpaper steamers work great for these and you can often find them on local classifieds. Use RO or distilled water in the steamer to avoid mineral buildup.
  • 3# Sledge - Used for coopering. I bought one at Lowe's, I think for less than $15. Actual cooper's hammers are available, but they usually start at around $75. This is really only needed if you need to tighten hoops and maybe if you run into leaking issues after filling.
  • Cold chisel - Used as a hoop driver. Again, a cold chisel from Lowe's is pretty cheap, while an actual hoop driver is around $75. Same as the hammer, you really only need this if you need to tighten the hoops. I used my benchtop grinder to flatten the cutting edge so that it doesn't slip off the hoop. Word of caution, use eye protection. 
  • Water - Use RO or distilled water for steaming, and always, always, always use de-chlorinated water for rinsing, filling, etc.
What I'm Starting With
This particular barrel is a 15 gallon American oak barrel coopered by The Barrel Mill, and has a #3 char. I acquired it from a friend that works with Sugar House Distillery.
  • Originally filled with Rye Whiskey.
  • Prior to my initial fill, the top 50% of the staves were waxed.
  • My initial fill was an Adambier in 2/2019
  • Adambier was emptied on 7/1/2019 and it's sat empty and bunged since then. 
  • Rehab began on 5/13/2020, so the barrel sat dry for 10 months
The first thing I did was inspect the barrel to make sure there weren't any major issues. Things like mold and structural issues are what I'm looking for. In this case, there were no signs of mold, no off flavors, and the barrel still smells like whiskey...all good signs that it's worth the effort to rehab. Here are some "before" shots to give you an idea of the condition of my barrel.
Shrinkage between staves and head

Separation between waxed staves

Gap between hoop and staves

Rehab Diary
Session 1, 5/13/2020 12PM - I'm stuck at home due to Covid-19 and I ordered a pouch of Bootleg Biology's Spring 2020 Sour Solera blend yesterday, so I decided it was a good time to start getting this barrel in usable shape. The primary issue is there's visibly noticeable shrinkage. 

I started out rehab with a 30 minute steaming session.  No real issues during the first session other than there are visible leaks between the staves. 

Water seeping out now between staves

At the end of session 1, I re-bunged the barrel. 

Session 1 results - definitely not water-tight

Session 2, 5/14/2020 8AM - I'm doing a 45 minute steam session this morning. 

No issues during this session. I'm still seeing leaking when the steam condenses. I forgot to take a picture of the paper towel under the barrel this time, but it was basically the same as after session 1. Depending on how things go after the next session, I may try tightening the hoops a bit. On the plus side, the barrel is  noticeably heavier compared to before steam session 1.

Session 3, 5/15/2020 8AM - I'm doing another 45 minutes for session 3.

Session 3 - getting closer to water-tight
There was a huge improvement after session 3. The paper towel under the barrel only shows a few drips. Compare that to sessions 1 and 2 where the paper towel was completely saturated. Spaces between the staves and hoops that I was seeing before session 1 have all but disappeared.
Exterior barrel temp after 45 minutes
I'll probably do one more steaming session before a French Method session. 

Session 4, 5/16/2020 8AM - Today I'm doing a 1 hour steaming session. 

No issues, and based on the way the paper towel looks, no leaks this time.

Clean and dry paper towel!
Since it seems the barrel has sealed itself back up, I'm going to pause the steaming sessions. For the next session, I'll do a modified French Method, where I stand the barrel on end and fill the head with hot water, flip, and repeat. After that, I'll fill the barrel with hot water and check for leaks. If all goes well, the barrel will be ready to receive beer. I'm planning on brewing Memorial Day weekend, so this barrel should be getting filled in the next couple of weeks.

Session 4, 6/14/2020 - On 6/8, I brewed the rest of the beer that will be going into this barrel. Since it's been a month since the last steaming session, I'm starting off with that today just to be safe.

The steaming session went fine and I followed it up with the French Method (partial fill with hot water, then flip on end and fill the head with hit water, soak for 15 minutes, flip and repeat). I then ended up filling the barrel with water and found a very slow leak near one of the heads where the head meets the chime. Unfortunately I didn't have time to do much with it before I left town for a week.

Session 5, 6/27/2020 - This session is kind of an exception rather than a rule. As I mentioned, I've used this process on several barrels including two 30 gallon barrels that were very dry. Normally the barrel would be ready to fill after session 3 or 4, but this particular barrel needed some extra TLC. The problem I ran into here was the leak was so slow that it was difficult to see where exactly it was leaking. These barrels use barrel wax in the joint between the chime and the head. Some of the wax had seeped out during the steaming sessions, so I reasoned perhaps the loss of wax was causing the leak. I ended up melting some paraffin into the outside joint with my heat gun and tested again. This seemed to fix things with the barrel partially filled, so I tried filling the barrel again. Unfortunately, when full, the slow leak reappeared. The good news is that after the paraffin application it was easy to see it was leaking out of the end grain of one of the staves. This kind of capillary leak seems to be relatively common and is usually pretty easily fixed. If it's really slow like mine was, sometimes you can fix it with a hammer, a dull straight chisel, and a couple well placed blows. Note: the chisel used for this is smaller than the one I use as a hoop driver; this one is about 1/2" wide. Essentially you're creating a dam by collapsing the capillary. If it's worse or the leak reappears, you might have to go the wedge route. If you have to go that route, here's a link to an excellent video from Barrel Builders that shows how to install wedges. Anyway, long story short, the barrel is now water-tight and ready to be filled. It's currently filled with holding solution (solution containing potassium metabisulfite + citric acid). I should also mention, I'm planning on doing the Solera method on this barrel, so I went ahead and waxed the heads when I was trying to fix the leak. The effectiveness of waxing is debatable, but the intent is to reduce oxygen permeability of the thinner oak (thinner compared to wine barrels). Once I'm ready to fill it, I'll rinse with de-chlorinated water before racking the beer for aging.