Why I'm not buying...
The main issues I have are these: first, that the concept is "secret", and second, that this seems intended to promote his own products as older than their barrel years, and third is the problem of comparing one's rums to others without real data about them. Accordingly, I emailed Philippe back:
Moi: "I would be very pleased to exchange ideas – your GSA is a very interesting concept. There is a consensus that aging in the tropics takes place perhaps two to three times faster, and I’ve seen it claimed that a year in the tropics is the equivalent of two or three in say Scotland. Of course there are other variables such as storage, ventilation and the average temperature differential, altitude, et al."
"I would love to know more about your GSA and how you went about comparing for example, the Barbancourt 3 Star (which is actually 4 years old, not 5) with the Zacapa 23. It is very difficult to ascertain the age of the Zacapa based on their blending system which is misrepresented as a true solera."
To which Philippe replied:
Rhum de France Rhums: "Dear Capn Jimbo,
The variables you mentioned are indeed part of the GSA calculation. Considering our fast a spirit will age under tropical climate vs temperate or cold climate is certainly subject to debate. I'd say 2-3 times faster but if there is any argument about it I may use the angel's share as a base (although I understand that evaporation is just evaporation and may not be linked with the relative age of the given spirit). For the sake of simplicity one could measure the ABV of samples taken from the casks at regular interval.
Their is somebody in USA who is doing artificial aging of spirits, his name is Daniel Watson, it would be interesting to get his perspective on that (not that I approve such practice).
When you say consensus about aging, it is indeed interesting as well. On one hand most rum producers working under tropical conditions will say that their rum age faster. They are even Brandy producers (I know at least one) moving their operations to the tropic not to mention another one (in France) who is buying rum aged in the West Indies and later bottled in France after a brief passage in cognac casks (you certainly know about "Rhum Plantation"). On the other there is the maker of ron Zacapa saying that because their rum is aged above the clouds at around 15 degrees it is better. Go figure.
Talking about Zacapa 23, it is certainly an above average rum, it has IMHO a very rich flavour profile (but that's because the rum is aged in about ten types of barrels named from A to J). They should call that "Zacapa Solera" or something. What else it is at least 6 years old and at most 23 but it is nearly impossible to determine the exact proportion even for the master blender.
To know the exact figure requires using fluid mechanic equations. again we use estimations to get a number and adjust it based on raw material used (in this case sugar cane syrup) climate data (not the entire Guatemala but the area where the rum is aged).
GSA does not give you the real age of the product but it's relative aged compared to say a spirit aged under tropical conditions at sea level (with an approximate angel's share of say 10%). From this perspective Zacapa 23 like most whiskeys and brandys with have a low GSA. Worse, it's a blend so that does not help. The highest GSA we got for 2012 is the Damoiseau 1953, aged exactly 31 years in oak barrels. It has a GSA of 28.
Sorry to say that the exact GSA calculation is a trade secret so we cannot give it out just like that. I know, sooner or later someone may try something similar, give it another name and try to make money with it but that's just life.
Happy Tasting!"
In so many, many words, Philippe does not really answer my very simple question, which was how he went about stating a specific BSA for Barbancourt and for Z-23 (with the little public data that exists). He admitted the lack of data, but failed to then address how his original email made the claim "
For instance a 5 years old Barbancourt (a rum we like) has a similar GSA to a Ron Zacapa 23,". Instead I got a wall of words and diversions reminiscent of a politician explaining how his picture got taken smoking crack...
Stay tuned...