Sunday, 16 March 2014

In-bottle Maturation Experiment

I tried my hand at ‘bottle ageing’ some whisky recently. The idea had first been put into my head after meeting William Borrell from Vestal Vodka at Imbibe Live last June. William had been experimenting with oak chips (sherry cask and bourbon cask) as well as other woods, within the bottles and there was a noticeable difference in both colour and taste within just a short maturation period.

Later Ralfy posted a couple of videos where he went about changing some cheap supermarket blended whisky through bottle ageing whisky, using different wood species to change the profile. I wanted to try this (you can find Ralfy's videos here: Part 1 and Part 2)

I wanted to use American White Oak (Quercus Alba) for my initial experiment and started searching for suitable wood. Initially I was hoping to be able to find some ex-bourbon barrel staves but ended up with a craft wood supplier and bought a handful of pen blanks, five American White Oak and five European Oak (Quercus Robur) virgin oak pen blanks.

Ideally I was hoping to find an uncoloured whisky, but every one of the supermarket single malts seemed to be heavily coloured. Not wanting to mess up a distillery bottling I picked a 12 Year Old Highland Single Malt from Tesco, in hindsight it was perhaps a little too dark already, but at just £21 was a low risk experiment.
I can do science me
Following Ralfy’s video I dried, then lightly charred the outer edges of the pen plank using a blowtorch. I wanted to give some sherry influence to the Highland Single Malt so, I made a small tray from some aluminium foil to soak my ‘stick’ in after charring. I used a glass of Oloroso, and left it to soak into the charred pen blank while I hunted for a suitable maturation container that would allow my pen plank to be suspended in it. My original idea was to use a kilner type jar, that has a nice wide neck and a resealable lid, but in order to hold the full length of the pen blank would have needed more than one bottle to cover the wood. I settled on using an old wine carafe that I had a lid for, and decanted the bottle of single malt into it, while keeping a sample for a control, so I could compare the differences later.

I suspended the charred and sherry soaked pen blank into the carafe and left for around 12 weeks. Initially I was checking it regularly to make sure I wasn't over exposing it to the wood, but eventually forgot all about it, leaving it out in the garage to continue the process.

Last weekend I remembered it and decided I needed to check it out, I also had some old bottles that I needed to get some spirit into them to stop the corks from drying out, so killed two birds with one stone.

There was a slight colour difference, which was easy to see in the glass, but perhaps not quite as easy to pick up in the photograph. The difference in the nose was more pronounced as was the taste, and I was pleasantly surprised with what I found.

Whisky Discovery #726

Tesco’s 12 Year Old Highland Single Malt
Highland Single Malt
Circa £25.00 70cl
This was the ‘donor’ bottle for my experiment and chosen because it was reasonably inexpensive and readily available:

Nose: Quite gentle floral notes, not dominating though. Gentle honey notes followed with a herbal heather note and some peppery spices too. Not overly complicated but certainly in the highland style

Palate: Opens with a herbal sweetness, grassy with heather and gentle citrus notes. Spices come through towards the end with some peppery ginger heat

Whisky Discovery #727

Tesco’s 12 Year Old Highland Single Malt (40% abv)
A Bedfordshire modified Highland Single Malt
The one on the left has been modified in Bedfordshire
Colour: A slight colour change was noticeable, with the 

Nose: Sweeter immediately, richer honey notes coming through to the fore and much enhanced spicy notes, the floral herbal notes had been overcome with buttery vanilla and the charred wood notes were evident

Palate: A greater wood influence was also apparent on the palate, with wood shop and sawdust notes, sweet honey notes and the spices seemed softer but overall a much richer mouth feel was achieved. The spicy heat comes through right at the end, and finishes much drier than the original whisky

I was hoping for more sherry influence from my experiment, perhaps I should have left the wood soaking in sherry overnight, or even longer. 

I would have liked to see a greater colour change, and for my next experiment I want to use some lightly coloured spirit, or new make if I can get my hands on some. I’d also like to use a higher abv spirit. I’m going to stick with my Oloroso conditioning as usually have a bottle or three to hand, but would like to run one of each American and European Oak in two separate flasks to see how different they turn out.

Not long after watching Ralfy’s videos and while hatching my own cunning plan I received and email from a local micro brewery. He had found our blog and wanted us to come and taste his English Spirit. Our local micro brewery was making a number of different beers for the local area, but every now and then would send a batch of his wash to a local distiller who would distil and bottle his English Malt Spirit at 40% abv, coloured with spirit caramel.

I discussed my in-bottle maturation experiment with the brewer who showed immediate interest and I pointed him towards Ralfy’s video blog. I need to follow up with him now and see how his next batch has gone down, as he was going to try some of his own experiments, he might also be my source of new make spirit for my own plans.

Then I was thinking…
There is a huge demand for whisky right now, distilleries have been caught off guard and there is a rush to expand capacity. New distilleries starting up on an almost weekly basis, aged stocks being consumed so fast that many brands have been abandoning age statement whiskies at the younger end of the scale, creating new NAS (no age statement) expressions allowing distillers/blenders to use younger stock with the older maturing stock to make it go further and get product to market to meet the demand.

The current UK law states that to be deemed whisky the distilled spirit must be matured in oak casks for a minimum of three years. New distilleries have been selling their distilled spirit, matured in oak casks, at younger ages, to raise necessary cash flow, but it cannot be called whisky.

When maturing spirit in oak casks a percentage of the spirit is lost every year due to evaporation (known as the Angels Share) H.M. Customs allow for two percent a year which can amount to over 50 litres over a typical 10 year maturation.

This new demand must increase demand for casks, both new for Bourbon and second-hand for Scotch whisky, and with distilleries worldwide all in the market for quality casks to mature their spirit in, perhaps now is the time to investigate alternative ways of exposing wood to the spirit?

I'm damn sure that I can't be the first one to think along these line, but closed containers with oak staves suspended in the distilled spirit, as per my in-bottle extra maturation experiment might be worth investigating on a larger scale. The planks could be thinner as all sides of the wood would be used, expensive quarter sawn timber would not be necessary as their would be no structural requirements. Yield should increase as the Angels Share losses should be almost eliminated. Perhaps with a larger volumes of maturing spirit, temperature would remain more consistent and with careful calculations just the right volume of oak wood could be used to maximise the life of the ‘plank’ whilst reducing the maturation time, and producing consistent quality. The oak planks could be pressure infused with Sherry, Port or any number of other wines currently used in cask form to finish whiskies, to create the whisky profiles we currently enjoy.

Perhaps this is a step too far right now, but surely things will need to change in the future? The demand on managed forests will eventually outstrip the supply of suitable cask timber, and how many times can a cask be 'rejuvenated' before it's lifeless?

I would love to hear your thoughts, but in the meantime I’m looking to start my next in-bottle maturation very soon, and perhaps an English Malt Spirit which has had oak influence in this manner might start a trend from the new craft distilleries.

Slàinte! Dave


Tom said...

Compass Box added flat French oak staves to their first two bottlings of Spice Tree, then had to stop when the Scotch Whisky Association threatened legal action ( They were able to work out a way of getting the flavor they wanted by playing about with the cask heads.

So yes, your idea is a good one, and yes, it's a step too far right now -- at least for the SWA. Is it a step too far for the consumer to buy something like "malt spirit"? Harder to say

Anonymous said...

It might be an interesting experiment - and one which it wouldn't surprise me if larger companies with R&D budgets have already looked at - however one key thing to remember about the cask aging process is that one of the key factors is the expansion and contraction of the wood over the aging seasons, which draws the spirit into the grain and then squeezes it out again. At a guess I'd say that a hermetically sealed inert container with a stick in it is going to release the wood compounds very differently to a "breathing" cask.

You could really go to work on this line of experimentation though - for instance seeing what difference the Euro oak stick makes to pale whisky when it hasn't had sherry soaking into it.

Julian Mächler said...

I was playing with the exact same thought. With increasing demand and distilleries running out of older casks I think there should be made investigations for alternative techniques. Maybe someone could experiment with new technologies and see if it works out. They couldn't call it whisky of course but if the new product would get good critics on social media it could still be commercially succesfull. I'm really looking forward to read further posts on this issue on your blog