Tuesday 28 March 2017

Experiments in Oak: a DIY Maturation Experiment

Hi everyone,
I decided to share some of my thoughts following a recent experiment with DIY maturation.
Yes, it’s super long. Sorry.

(Disclaimer: I am not a Biologist or Chemist and I could very well be full of shit)


The wood is king. You can talk all day about barley type and origin, mashing temperatures, clear or cloudy wort, fermentation time, yeast type, distillation cut timing, condenser temperature, etc. The whisky in the bottle will have the majority of its flavour coming from the wood it has spent years maturing in. Some people say 60%, Gordon & MacPhail say 80%. Of course, it is dependent on how long the whisky has spent in the barrel in question. A 50 year old whisky from a 1st Fill Sherry Quarter Cask might be 99.99%.

After reading around oak, maturation and other parts of the process I was left wanting to know more. One of the burning questions to me was this: Could you mature whisky on a much smaller scale with a smaller piece of oak? This question was really raised and attempted to be answered by Ralfy in his video series on amazing whisky improvement technique. He was attempting answer a slightly different question though; he was looking at woods other than oak to mature whisky.

To me, if you can miniaturise the maturation process and therefore speed it up (with the increased surface area:volume ratio) then you can experiment a lot faster with different variables of maturation without getting into the real thing and waiting years to see if an experiment has worked.

People other than Ralfy have tried this as well, including here on Reddit. Since then lots of products have come out as well, claiming that they can mature whisky faster, including mini barrels, wooden bottles and these fancy oak sticks.

However, others in the past have not considered a few factors. The main one is the higher strength of ethanol in maturing whisky. Oak has to be activated through toasting and charring. This process breaks down the hemi-cellulose and lignin in the oak to produce Vanillin and other flavour active chemical compounds. Great, most do this with their experiments. However, Lignin continues to break down in contact with high ethanol levels (ethanolysis) to produce a variety of flavour activate compounds. Therefore, to receive a more accurate result we need to use high strength spirit, 63.5% would be best as this is the filling strength of most whiskies.

Other factors that can affect the accuracy of smell and taste of micro maturation would be: the time matured, the oak surface area to spirit ratio, the environment matured in, simulated breathing of the barrel/controlled oxidisation. Ideally, you would use new make spirit or a bland whisky at a high strength to accentuate the flavour differences from the original product.

So, a few research questions:
Can you take a stick of oak from a tree and mature whisky with it (ala Ralfy)?
Will this ‘young’ oak differ in taste and smell from fully mature American Oak (usually 80-100 years old and dried for a few days to months before use)?
How much will different seasonings (Sherry, port, etc.) effect taste and smell?
Is there a difference in smell and taste between toasting and charring?
Can the maturation process be miniaturised to a smaller scale?


Yes, you can mature whisky with a stick from your nearest oak tree, as long as it has been treated with the same toasting/charring process as a normal oak barrel.
Yes, it will differ in taste considerably. I would have thought it would have its own unique characteristics.
Different seasonings will significantly differ the taste and smell of whisky due to indrink.
Yes, there will be a significant difference in smell and taste between toasting and charring.
Yes, the maturation process can be miniaturised. It’s just getting all the Goddamn variables lined up.


Since I don’t have access to new make spirit, I have used a 10 year old cask strength Caol Ila at 60.1%, matured in 1st and refill Sherry Butts. I poured 2 ½ cl into 6 3cl bottles.
Rather than a full maturation I decided to try and carry out a ‘finish’ to the whisky in 4-5 days.

I cut a small stick of oak from a nearby tree, it should be either Quercus Robur or Quercus Petraea but I was unable to tell the difference, in either case it would be European oak.

I took a small piece of American Oak from an actual barrel stave (they were dismantling some display barrels at work). It was untreated and unseasoned from the chime (the end of the stave that sticks out beyond the end of the barrel).

All oak pieces (5 from the young European oak and 1 from the mature American Oak) were toasted at 150 degrees centigrade for 1 hour. Not all were the same exact size, but as similar as I could get them.

All but 1 oak piece was charred with a Butane blowtorch for 1-2 minutes. There was some variability with the charring as it was done by hand rather than machine. The piece only toasted was of the young European oak.

3 pieces of the young European oak were seasoned for 1 day with Port, Pedro Ximenez Sherry and Rivesaltes respectively.

All oak pieces were inserted into the 3cl bottles with the Caol Ila and left for 4-5 days.

Samples were then compared together to see whether they differed in taste and smell.

I then left the samples for a few months and am now doing a final comparison.


The oak floated at first and very tiny bubbles were observed coming out of the wood. I assume this was the wood absorbing some of the whisky (known as indrink).
After 24 hours the wood had sunk to the bottom of the bottle.
After 48 hours the small bubbles had usually stopped completely.
Colour got darker on all samples. The original colour was light Gold, the finally colour was Gold-Light Amber, depending if there was any seasoning.


Original Tasting notes: Caol Ila 2004 G&M 60.1%
Colour: Light Gold
Nose: Clean mineral smoke, salt water, malt.
Taste: Sea water and lemon juice. Clean smoke.
Finish: Very mineral.
Full tasting notes can be found here.

Toasted Young Euro Oak Finish 5 day
Colour: Gold
Nose: Similar but different. White bread, permanent marker, much more woody.
Taste: White bread, woody, but more similar to the original than the nose.
Finish: Mineral and slightly fishy (not in a good way) with a vague coffee bitterness.

Charred Young Euro Oak Finish 5 day
Colour: Gold (Slightly darker than Toasted)
Nose: Instantly darker in aroma than Toasted. Brown bread, earthy, chocolate and over-ripe citrus fruit.
Taste: Brown bread, coffee beans, earthy, rotting limes, bitter young oak off note.
Finish: Rotting limes and that young oak thing.

American oak Charred and Toasted Finish 5 day
Colour: Gold (Same as the Charred Young Oak)
Nose: Much more recognisable character. Vanilla, toffee, fresh citrus, smoke, sea water, lemon juice.
Taste: Smoke, much more than any of the others. Fresh lemon, some toffee and fudge, barrel char, charcoal.
Finish:Charcoal and lemon juice.

Pedro Ximenez Sherry Finish Charred Young Oak 4 day
Colour: Gold
Nose: Roasted coffee beans, light raisin, much less smoke than the others.
Taste: Much sweeter, raisin, young oak off note, bitter, harsh charcoal.
Finish: Lemon burst.

Port Finish Charred Young Oak 4 day
Colour: Light Amber
Nose: Much more intensely fruity, blackcurrant, blueberry jam, dark chocolate.
Taste: Lemon, light blueberry, intense smoke, peppery, charcoal.
Finish: Young oak off note and harsh charcoal.

Rivesaltes Finish Charred Young Oak 5 day
Colour: Light Amber
Nose: Parma ham, celery, no smoke, red berry, a hint of sulphur.
Taste: Sulphur, smoke, young oak note, charcoal, red berry, coffee.
Finish: Chewy with sulphur, smoke and red berry.


Let’s have a look at the hypotheses:
Turns out you CAN take an oak stick from any old oak tree and use it to finish your own whisky. However, the young oak had a definite off note. The young oak note was quite unpleasant and I haven’t found it anywhere else. It’s a little like rubbery cardboard. It also did NOT take well to being charred. It seems to create a pretty unpleasant charcoal note that was particularly noticeable in the finish of the whiskies. The combination of these off notes is convincing to me that 100 years of growing definitely helps the oak to develop, perhaps something to do with the growth rings (I would love to meet a Biologist with a specific knowledge of oak trees).

The mature American oak had much nicer notes of vanilla and toffee, although still suffered a little from the charcoal note. Perhaps it was the butane blowtorch charring that caused the burnt off note.

The seasoning seemed to affect the flavour of the whiskies as well; the most successful here was the Rivesaltes. I’ve found it is hugely important to pair the wood with the seasoning and then with the whisky. A light white wine would not be able to stand up to European oak and then to a big smoky whisky, it would have no effect. The porousness of the oak would be important as well, PX Sherry can have a very thick consistency and may take a lot longer to penetrate deeper into layers of the less porous American Oak (this is to do with the Tyloses in American Oak rather than the grain of the wood).

There was a definite difference between toasting and charring and again it would be important to pair this with the seasoning and then the whisky. Here the blowtorch effect of the heavy char note slightly ruined things, again could have been the Butane, I’m not sure what fuel they use normally. The toasting seemed to have a much lighter flavour than the darker and more intense charring.

I believe that the process of maturing whisky can be miniaturised accurately, but it’s very difficult. However, micro maturation seems to work best as a finishing to blander whisky that doesn’t have too much flavour already but that is also cask strength. It also helps if it is natural colour as you can then track any colour change.

Therefore I wouldn’t see it ever being really useful, but absolutely interesting and helpful in understanding the multitude of variables involved.

Further research:
Does the ethanol strength of the whisky make a difference to the taste and smell of micro maturation? 40% vs 60%
Does the environment of micro maturation affect the taste and smell?

If you managed to read it all, thanks for reading and let me know your thoughts!
For those that skipped down here TL;DR: It is possible to change the flavour of your whisky with DIY maturation, but it’s really hard to accurately replicate full barrel maturation.

UPDATE: From some comments made on this post on Reddit, it seems that the seasoning process was rather more elaborate than I had thought. Many places not only kiln or air dry the staves but leave them to season out in the open for many months before this process. This would have the effect of the natural weather conditions slowly leaching much of the tannins and other harsh falvours out of the wood before it then gets dried and made into barrels. Something to consider for future experiments. 

Thanks for reading!

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