[Update: See the follow-up post here.]

Warning: this is long and symptomatic of obsessive compulsive disorder, and in any case may be something you already know or don’t care about. If you do choose to read the whole thing what are you going to find? Well, after a long’ish setting of the stage in which I describe how I came to think about this issue at all and the conversations that led me to explore it further, I detail how I came to discover that the term “Single Cask” may not refer to a whisky that was matured for its entire life in one cask; and furthermore that the cask type stated may not refer to the only type of cask in which it was matured. My chief reference here is to the Glendronach distillery but I suspect this is far more broadly applicable.

The Part Before The Interesting Part (But You Should Read It Anyway)

As I’ve noted before, I am a big fan of the Glendronach distillery in its current incarnation (I have little knowledge of the malt put out at Glendronach before it was taken over and revamped by Billy Walker and co. from Benriach). I enjoy the 15 yo Revival and 21 yo Parliament in the core range but it is the annual releases of batches of single casks that most excite me. I’ve not had so very many of these compared to some, but I’ve had more than a few and I’ve found them to run the gamut from very good to excellent. And that, by and large, has arguably been the response of most whisky geeks (well, maybe not of the few who insist sulphur taint is an ongoing problem at Glendronach).

As such, it was a little jarring to see a poor review of a Glendronach single cask at Whiskynotes earlier this week, a 21 yo cask from a single PX puncheon (#5405)–this was of interest to me as I recently purchased a bottle from a 23 yo PX puncheon (#1240). Now a poor review in and of itself is not such an interesting thing–though when it comes from a source as influential as Ruben at Whiskynotes it means more than it normally might (and after the fact I see that Serge didn’t care much for that cask either). Things got more interesting in the comments where Arild Een pointed out that 702 bottles from a puncheon after 21 years seemed like a lot, and pointed readers to a negative review by Ralfy Mitchell of another PX release (alas, my cask 1240). In this review Ralfy raises the issue of cask 1240’s unusually high outturn of 647 700 ml bottles from a puncheon and speculates that what may be happening is that more than one less successful cask had been re-racked into a larger puncheon for a short period of time. This he suggested would explain both the large number of bottles and what he found to be an overbearing PX influence.

[A quick pause for arithmetic: 647 700 ml bottles is about 453 liters of whisky. The typical puncheon holds 500 liters of spirit (as far as I know). Spirit loss during maturation (the so-called Angels’ Share) is said to be 2% a year. A loss of only 47 liters over 23 years, and almost all of it alcohol–the cask was bottled at 50.8%–seemed weird.]

In the comments on Ruben’s post I speculated that another possible explanation for the high outturn and low abv might be that the cask had not in fact been bottled at cask strength. In fact, those words don’t appear on the label (probably true of all in this series). It was possible, I thought, that after 23 years the PX had completely overpowered the spirit and thus it had been diluted to make it more balanced. Another commenter (MARS) noted that puncheons can apparently be as large as 600 liters and that there was therefore no reason to think that the bottle reviewed by Ruben (and extension the one reviewed by Ralfy) was from anything but a single cask.

Flash forward to a brief discussion of the issue on the WhiskyWhiskyWhisky forum where I brought up the issue of cask 1240’s outturn and Ralfy’s speculations. Another member (Bobag) weighed in to note that they had purchased a bottle from a 20 yo single cask from 1993 (Batch 9) and that the cask number (Cask 5) was the same as that of the 33 44 yo Glendronach Recherché released the prior year (Cask 005; this can be verified on Glendronach’s website). Bobag noted that the staff member at the store the bottle came from had said that he thought that the 20 yo, 1993 from Batch 9 had been “finished” for an additional year in the cask in which the Recherché had been matured. This seemed dubious to me, not least because a cask that had held spirit for 44 years seems like a poor choice for “finishing”, as it would doubtless have little to impart.

The Interesting Part

At first I thought I would just throw up a brief blog post and invite people to shed any light they could but on second thought that seemed irresponsible. I did not wish to invite public speculation on a distillery’s practices that might erroneously put them in a bad light. Instead I sent the distillery the following email:

I have some questions about some of your single cask releases that I am hoping you may be willing to clear up for me: 1. Are your single cask releases (in the various batches) bottled at cask strength or are they sometimes further diluted? 2. Your 1968 Recherché is said to come from cask 005, an oloroso butt. but there’s also a single cask 1993, 20 yo from the 9th batch which is said to be from cask 5, also an oloroso butt. Are these the same cask? If so, was it the case that the 1993 20 yo was matured in some other cask(s) and then finished in cask 5? 3. What size are the puncheons used at Glendronach in the past? I ask because I have a bottle of the 1990 23 yo from a single PX puncheon #1240. This produced 647 bottles at 50.8% which seems like a very high number of bottles from a 500 liter cask (as I assume most puncheons are). Or is this kind of an outturn normal even from a 500 liter cask? I would really appreciate any clarifications you can offer about these questions. I am a big fan of Glendronach and as I’ve seen doubts raised about these issues recently I am hoping to arrive at some understanding of them. I am considering writing a blog post about these conundrums and would prefer to have input from the distillery before I proceed.

The following morning I received a very detailed response. I had a few follow-up questions and in asking them I asked if I could quote the email I’d been sent (as I do not wish to inadvertently misrepresent the distillery). While the contact at the distillery once again answered all my follow-up questions in great detail he asked that I not quote his emails. I am therefore providing only a summary of the key points in his responses to the questions above and also to my follow-up questions. I found the answers fascinating and I was very appreciative of the speed and detail of the replies (though I don’t quite understand the refusal to be quoted; I think his willingness to respond clearly to a customer only puts the distillery in a good light). It raises for me questions that go well beyond Glendronach (but more on that below).

Here is what I took away from our email exchange:

1. Cask numbers at Glendronach are re-allocated each year that they are filled and thus there’s a Cask 5 every year that casks are filled.

[So Cask 005 from 1968 (Recherché) is not the same as Cask 5 from 1993 (Bobag’s 20 yo from Batch 9).]

2. The bottles released in the single cask series are never diluted and are always bottled at cask strength, unless a specific retailer asks for a lower abv of 46% for an exclusive bottling.

[This means my dilution hypothesis above was entirely wrong.]

3. Glendronach does indeed re-rack more than one cask into a fresher cask in its single cask batch releases. The vintage listed on the bottle is the original vintage but the cask number is of the latest cask used. Therefore if you have a bottle of Cask 8383007 from the 1990 vintage this means that all the whisky in it was distilled in 1990 but it is entirely possible that more than one cask of whisky bottled in 1990 was matured for an additional period in Cask 8383007 which may have been filled in 2000 or 2006 or whenever before being bottled in 2012 or whenever. I was given to understand that such re-racking at Glendronach occurs many years before the re-racked spirit is bottled.

[This would additionally rule out the notion that the 20 yo from Batch 9 was re-racked for only one year in the Recherché cask.]

Now this is where it gets a little muddier.

4. There is no guarantee that all the whisky that may have been re-racked into a PX or oloroso butt/puncheon at some point in the maturation was originally in the same kind of sherry cask.

What all of this amounts to is that “Single Cask” does not necessarily mean what you might take it to mean. It certainly does not mean what I had always taken it to mean at face value: the contents of a single cask matured for the full term in that cask before being bottled. Your bottle that says 23 yo Single PX Puncheon #12345, 1993 on it will only have 23 yo whisky from 1993 in it but that’s about as much as you can take for granted. It may not have started out its life in PX Puncheon #12345 and indeed it may have started out its life in an oloroso butt or possibly even a combination of cask types before being re-racked into PX Puncheon #12345.

There may, however, be clues on the labels. If you had been able to zoom in on the group picture of a bunch of bottles from various single cask releases at the top of this post you would have noticed that only one of the labels states explicitly that the whisky was matured in one cask for the years stated. The rest merely state the cask type and age. Unless told otherwise I am going to assume that this is how we can know if a bottle is from a full-term matured cask or not. Click on the thumbnails at left to enlarge and see for yourself (look at the sentence below the vintage statement). This, I should clarify, is my own reading of the discrepancy in the label text and not anything that came out of my correspondence with the distillery. If you have any of these single cask bottlings in your collection perhaps you could check to see if any of your labels also seem to specify single cask maturation.

The Part after the Interesting Part (Now That You’ve Come This Far You May As Well Keep Going)

Now, how do I feel about all this?

1. Well, I feel surprised but not cheated. I am not buying these whiskies because I think they have been full-term matured in a single cask but because I expect them to be very good whiskies. The practice itself seems entirely legal, and it is seemingly required that the cask number and type refer to the last cask. And I suspect that it may turn out to be common practice across many distilleries. Indeed, I am surprised in retrospect that I didn’t follow this train of thought further when reviewing this Ben Nevis 25, 1984.

2. I also don’t think that it necessarily follows that the “bad” Glendronach single cask releases are from such hybrid maturations whereas the “good” ones are from full-term single cask maturation–as Ralfy’s review perhaps implies. My sense from the email exchange is that this kind of re-racking is just part of the normal cask management regime at Glendronach and indicative for them of the exacting care they take of their casks.

3. The other takeaway is that one should not shy away from a cask only because it lists a particular type of sherry on the label and you don’t care for whiskies matured for long periods of time in that kind of sherry casks. One should also not be quite as confident in asserting characteristics of full-term maturation in specific sherry casks to whiskies that may in fact have more hybrid origins. If you hate PX matured malts but have been trumpeting your love of an oloroso matured single cask Glendronach, then, for all you know, you may have been praising a malt that spent more time in a PX cask than in an oloroso cask.

4. The chief takeaway, though, for me, is that the Scotch whisky industry needs clearer and more transparent and consistently used definitions for the terms distilleries use. Whether it be “Cask Strength” or “Single Cask” or a reference to a cask type, consumers should know what these terms mean and they should not find out that the common sense meaning is not the one the industry uses. Otherwise this could lead to a sense of suspicion even where one is not warranted. And, again, it seems likely that the practice is far more widespread.

All this said, I would urge Glendronach and other distilleries that do this kind of thing to be more transparent. Describe the maturation regime clearly on the label as Springbank, for instance, do for their Wood Expressions line. You may need to print custom labels for the bottles from each cask but that seems a minor burden in the service of transparency. The more upfront and forthright you are about your practices the more customers will appreciate you, and this will do more for your brand, in my opinion, than secrecy or coyness ever will.

So, do you (my readers) know more about this kind of thing? Have you (and everyone else) known it all along? How do you feel about it? Is my view too naive? I look forward to reading your views in the comments.

[P.S: I am also looking forward to opening my bottle of Cask 1240 soon. It has a very different rating on Whiskybase than the usually generous Ralfy gave it and I’m intrigued. I’m hoping, of course, that my experience will be closer to those of the Whiskybase raters.]

[Update: See the follow-up post here.]