February 21, 2012

Paraffin waxing a barrel.

So after adding dates to the small 5 gallon barrel, fermentation started again and I noticed the S-airlock burping.  The next day however it wasn't burping, but there was maintained pressure on the water in the S.  I was a bit confused at why that would be.

Now, the 5 gallon barrels I have were previously wine barrels (a plus) that had been sitting on display for 2 years (a minus).  Needless to say, they were not in the best of shape when I got them.  The barrels did swell tight, and after I steamed this barrel, I think it should be good to use.  However, given its past, I started wondering if the staves on the top of the barrel (where no beer is directly in contact with) might not be drying out and the joints separating just enough to let out some of the C02 produced during this fermentation.  (Note: there isn't really an issue with gases escaping now, however, if gas is allowed to enter through these same cracks later, we run the risk of acetobacter ruining the lambic)  So I decided to test this hypothesis:
Soaking the barrel's top staves from the outside.

Here I have a piece of wet cloth covering the top of the barrel.  In a few minutes the barrel started burping!  With my hypothesis proven, I kept the cloth on the top of the barrel, and kept it wet, for about 24 hours swelling these staves from the outside.

I know paraffin wax is commonly used on barrels.  When people don't want oxidation or the oak flavor to be imparted on the contents of a barrel, it is poured into the inside and allowed to coat the interior.  Obviously I don't want to seal the whole barrel as lambic greatly benefits from that slow oxidation oak provides.  I do, however, want to seal part of the barrel.  Now that I've re-hydrated the top staves so they are air tight again, I want to lock that in by paraffin waxing just these top staves.

Prepping the barrel before waxing it.
First I tape off a line at about 1/3 of the way down.  This is far enough down that the level of the beer inside should always be safely above.

Coating the top of the barrel with paraffin wax.
The next step is to coat the barrel with paraffin.  I melted a couple blocks in a metal tray and then simply scooped it on with a spoon.  This allowed me the control to make sure every bit of the target surface was covered with wax.  I could stop here, but its a bit ugly looking with a lot of unnecessary wax.

Melting off the excess wax.
To remove the excess, I took a blow torch and melted the wax from the top of the barrel down.
WARNING: If you are using a spirit barrel for the first time, do not do this until you have filled the barrel!

All of the excess wax has been melted off leaving a clean finish.
As you can see, this leaves a clean looking finished barrel.  Only a thin film coats the barrel, and that is all that is needed.

Finished barrel with wax only on the top third.
Finally I remove the tape and paper protected the rest of the barrel and you can see the final product!  The burping of the airlock has really picked up, even more than after just swelling. 

One complaint people have about using 5 gallon oak barrels is the higher surface area beer has to oak, and so the higher level of oxidation that occurs.  It makes me think that this might be a good thing to do even if your staves are air tight.  I'm not sure how to calculate it, but I'm sure one could figure out what percent of the outside of a 5 gallon barrel should be waxed so that it results in the same relative oxidation as a 60 gallon barrel.  I wouldn't be surprised if its the whole outside except for the heads!

Update (02/23): I added the dates (that provided the sugars for a new fermentation) 5 days ago.  Since waxing the top, the airlock has been burping about every 7 seconds.  Compare this to not burping, and then only burping about every minute after swelling the top.  While swelling the barrel from the outside certainly helped, there was still a considerable amount of gas allowed to escape through the stave joints.  I feel as though by doing this I have avoided serious problems down the line and hopefully saved the integrity of the lambic in this barrel.  Conclusion; I HIGHLY recommend doing this to your barrel if it had sat empty for any substantial amount of time.

Further Update


gamb0056 said...

Awesome post! I've been hesitant to buy a 5 or 10 g barrel due to the o2 permeability issues. This seems like a good solution. Any ideas about how to better estimate how much of the barrel to wax?

Levi said...

To estimate how much of the barrel to wax, you would want to figure out the "surface area to volume" ratio of a standard 225 liter barrel. Then use that ratio to apply it to the volume of your barrel to figure out how much surface area should be there, and then wax the rest.

I did some rough calculations, and for a 5 gallon barrel, leaving the heads unwaxed, you would want to wax 75% of the staves. For a 10 gallon barrel, leaving the heads unwaxed, you would want to wax 50% of the staves.

Now, this is assuming 2 things:
1.) That 225 liter barrels are optimum. I know Drie Fonteinen prefers 400 liter barrels. If you used that to set your ratio, you would be covering a higher percent of your staves.
2.) That by waxing the staves it completely eliminates o2 permeability. This is obviously not accurate and so here again I would cover a higher percent of staves.

With those two caveats, one could likely justify waxing the entire 5 gallon barrel except for the heads, and probably ~75% of a 10 gallon barrel's staves leaving 25% and the heads unwaxed.

gamb0056 said...

Thanks! I suppose that you'd also be assuming that the staves are the same thickness and that the porosity of the wood is the same (relative to the appellation of the wood, French v American oak, etc.)

Raje Apte's data on volumes and O2 permability of various vessels provides a good starting point, but well have to figure surface area of the barrels.

According to this:
a 5 g barrel has about half the surface to vol. as a 60 gal (~225 L), so your calcs seem about right if one wants to achieve a permeability somewhere in the range of a 225 - 400 L barrel (all other assumptions holding true).

I'll have to give it some more thought and research. Thanks! Love your blog!

gamb0056 said...

^edit above: the 60 gal has half the surface to volume as a 5 gal

Matt said...

I'm considering doing a primary fermentation in my 5 gallon barrel. I'm considering waxing the whole barrel. Is it a good idea to primary ferment in a 5 gallon barrel and would waxing the whole barrel be a good idea?

Levi said...

Matt - see comment above. I would recommend waxing the whole circumference of a 5 gallon barrel, but leave the heads unwaxed.

Unknown said...

So for a 15 gallon barrel I should wax 50% of it, and leave the heads unwaxed?

Levi said...

@Unknown - Yea, that sounds about right. Error on the side of covering more than less.

Leah CG said...

What about removing paraffin from the inside? Have heard boiling water. What about toasting to remove. Intend on sour beers

Andrea Filippini said...

Hi Levi! Fantastic post, very interesting reading here in Italy! Can I ask you which kind of paraffin did you use? And what about beeswax?

Levi said...

@Andrea - I get the paraffin wax from the grocery store. The kind that is used for canning. I think beeswax would work just as well if that is easier to get.

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