NOTE (6/7/16): I have edited this post to reflect some new information I learned from a winemaker here in Australia. He told me never to use citric acid in a barrel holding solution because it is actually fermentable. Because of this, the barrel has the possibility to grow mold and bacterias. He is an ex-microbiology lecturer and his wines are excellent so I am going to trust him. SO…. read on but note the change of acid.
Additionally, note the change of dosing rate. After a discussion on The Sour Hour and a few other online chats… Milk the Funk link has lowered the recommended potassium metabisulfite dose. This was due to Jay (Rare Barrel) noticing some sulfur off-flavour carry over with the higher dose. Enjoy…..
This topic has been covered very well by Jay Goodwin of the Rare Barrel multiple times on the Brewing Network podcast he hosts The Sour Hour. The problem is, I kept forgetting the ratio’s and had to re-listen to the second episode about 4 times before deciding to just write this down. What follows is an elaboration of how The Rare Barrel preps and stores their barrels with a additions of Chad Yakobson’s methods at Crooked Stave.
When The Rare Barrel receives ‘new’ barrels from a winery or distiller they first inspect them. Look at the outside for anything that may cause a leak like a splinter in the staves, which look like which toothpicks. These should be carefully removed not to further the problem and the affected area sanded back.
Additionally, check for signs of previous leakage from the former substance. If you can see thick, gooey wine or whiskey residue causing localised staining, scrape it off and take note of the site as this could be a future site to fail a leakage test. Fruit flies love these leaks too, and fruit flies carry acetobacter which is bad news.
Lastly, check that the staves are tight. If they have gaps between them, the barrel has been left empty for some time and they have dried out which is problematic for two reasons. Firstly, a loose barrel will not seal properly so you must add water to allow for the barrel to swell and rehydrate. Secondly, empty barrels are breeding grounds for all kinds of bacteria and yeasts. While you may hope to sour in your barrel anyway, the stuff that grows in here is not the stuff you want. If your barrel is dry, you should storage steps outlined below before filling your barrel.
Next take a flashlight and visually inspect the inside. Can you see mold or smell anything off? These are not deal-breakers but do indicate some poor treatment in their previous life. Also, some winemakers use wooden spirals or cubes to increase their oak surface area contact and consequently oak flavour. You will want to get those out too which can be done through rinsing them a few times and dumping what comes out.
At Crooked Stave, Chad and his team go the extra step of disassembling their barrels. This can be done by removing the hoops on one end and removing the head. With the inside of the barrel is exposed, you have a much better chance of catching imperfections which could lead to leakage, harbouring bad bacteria or imparting undesirable flavours from the previous substance. Barrels can develop splinters inside them which can evolve into a blister which often harbour acetobacter. Chad mentioned that they partly shave their staves back to expose new oak too, a process he calls ‘relivening’. This process reminds me of Cantillon’s famous barrel cleaning contraption which tosses around a heavy chain inside it to scrape the insides of the staves. Watch the below video if you haven’t seen this device, its quite medieval. Through this process, Chad said that they have never thrown out a barrel or had one go bad on them, so the extra time must pay off. I have also attached below a pdf about barrel maintenance which goes through the steps of removing the head much better than I can explain.
The next step in your inspection is to check for leaks. This can be done lots of ways, but the easiest way is probably just to fill it up. Be careful when you are filling as to not spill water on the staves, that makes it pretty hard to discern what is spilled water and what is a leak. You are looking for seeping through the staves or head.
Another way to check for leaks is to fill the barrel with about 15-20 l (4-5 gal) of water and cap it with a one-way bung which are common in the wine industry and should be easy to find. Then with compressed air, apply 4-5 psi to the barrel and allow the water to attempt to escape one head, then the other and finally the staves by placing the barrel on castors to rotate or simply roll it. The internal pressure will urge the water to find gaps that will become leaks. This process uses much less water and is less cumbersome. There is good video which shows this below.
Another way to check for leaks involves filling the barrel with 15-20 l (4-5 gal) of hot >60C (140F) water, inserting a well sealing silicone bung and letting the water cool which creates an internal vacuum. After about 20 minutes, remove the bung. If you feel resistance and air rushes into the barrel, you have a good seal. If there is no negative pressure inside the barrel, you probably have a crack that has allows the exterior atmospheric and internal pressures to neutralise.
If your barrel does have a leak and you are committed to using that barrel, you obviously need to repair the damaged area before filling. I know very little about this part of the process and I have not heard it covered by many brewers; however, I came across a great little video about it which is fairly straightforward which if you needed is better than nothing. The below YouTube video outlines repairing leaks from the Seguin Moreau cooperage in Napa. Their website also has some great resources for barrel care here.
Using & Storing your barrel
Every time you have an empty barrel, its good practice to give it a little love but especially if it’s your first time using the barrel a small treatment is in order. For your first fill, your main goal is to neutralise the barrel killing what may have previously occupied the wood. Just like CIP practices, you can basically go down heat or chemical paths.
I have filled barrels with water from our HLT at about 90C (195F) and allowed them to sit to kill any microorganisms with success; however, I would not recommend it for the danger is poses, the huge consumption of heated water and it’s a pretty ad hoc method without guaranteed results. You will achieve much better and more consistent results by pumping the barrels with steam. However, if you don’t have a steam generator sitting around the chemical methods work very well too.
The most ‘traditional’ option is to buy sulphur sticks from winemaker suppliers. Most brewers I know, however, don’t do this and opt for chemicals they mix with water. Most popular among these, potassium metabisulfite, is not only a great antioxidant but also a tiresome bacteria fighter. Mixing this with citric acid is emerging as a favourite method among brewers.
To make the solution fill your barrel about halfway and mix 0.127 g/l (0.017 oz/gal) of potassium metabisulfite with 1g/l (.12 oz/gal) of TARTARIC acid (see above) and top off the barrel. Allow the solution to set until you are ready to use. This is also a great storage solution for your barrel, so if you are not using your barrel for up to 6 months, just leave this solution in. For storage greater than 6 months, you are probably fine but it is best to dump and re-mix the solution.
When you are ready to fill your barrel, rinse it with hot water to remove any of the remaining chemicals in the barrel. Just before you fill, make sure you flush it out with CO2!!!! While the staves will allow a slow (good) oxidation over time, you should aim to minimise oxidation at every step along the way. In the same vein, fill your barrel gently and always from the bottom.
When your beer has finished its ageing and you have again an empty barrel, choose the heat or chemical options above to give your barrels at least quick treatment. Similar to washing your yeast, this step is not really necessary depending on what you are doing afterwards with that barrel however it’s a great insurance policy. Between uses, Chad at Crooked Stave always fills his barrels and foeders with a mix of a Birko chemical product called Acto 140, which is a barrel cleaner and similar to PBW but it has no surfactant in it so it rinses right out. Then they always fill their foeders with the same potassium metabisulfite and citric acid solution and hold them until they are ready to fill as well.
How to age your barrels is a whole new topic, but this should get you started in getting them ready and filling them up. I will continue to add to this post as I hear of new, effective methods. If you have something to add or edit, please contact me so I can edit.