Blender’s 30% ABV White Bubble Test

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We are exploring rum blending. These posts intend to be extra inclusive and aimed at engaging other content creators. Take any ideas and run with them! It is inevitable that basic blending becomes important to the rum scene so jump in as soon as you can!

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Evaluating spirits at lower ABV’s has been a common trick used by spirit professionals for generations but becomes particularly useful for understanding a spirit’s blending personality. It may even be a better starting point than the exhaustive test. The white spirit bubble becomes a useful tool for cutting small samples down to a precise ABV for making apples-to-apples comparisons. You simply pour 20-25 ml, no matter what the starting ABV, then you add water until the bubble stays suspended and you have fairly perfect proofing down to 30% ABV.

[White spirit bubble’s are for sale at $20 USD. Spirit bubbles were first made as a challenge from a few distillers, and at the time, we did not realize they were so useful; to us, they were simply historical. What we have found is that they can help you perform certain tasks, fast, small, and accurate. Small, means they quickly pay for themselves in sample volume saved. We even thought the white would be the least used of the sets, but that is turning out to be the opposite and I now use it to evaluate every spirit that crosses my desk.]

Some of the old German rum appraisal routines require appreciable spirits dilution. An ABV of 30% was a common number, but variations are described by Kervegant that dilute more significantly and even use hot water for high ester rums:

For the appreciation of rum and arak, the “grog” test is also often used. The product is diluted with hot water, so that the alcohol content is reduced to 10% or 5% (sometimes 1-2% in the case of very aromatic rums), and the odor and the flavor of this dilution, with and without added sugar. This test makes it possible to detect, more easily than tasting of the product straight, the presence of fine and delicate aromas, masked, particularly in the case of grand arôme rums, by certain esters. The volatility of ethyl acetate is also reduced by the water and the somewhat pungent odor of this esters is attenuated.

It is fascinating that they practiced variations with sugar to coax out aromas. It has been remarked in some of the old German literature that some rum aromas will not appear until a spirit is diluted, either with water or by stretching with lighter spirit.

30% ABV has been a sweet spot arrived at by many contemporary sensory scientists. Wüstenfeld & Luckow diluted their first four birectifier samples to roughly 30% while Arroyo diluted his further. Ethanol is to some degree a sensory distraction while on a physical level, some molecules become more volatile as ABV drops. Higher ABV spirits can be so tightly wound around ethanol that many features are hard to perceive.

Drinking a spirit at 30% ABV is like experiencing it fully open and resembles what is practiced by many Scotch and Bourbon drinkers. For academic appraisal, we are looking for assets & liabilities within a spirit. We are either searching for quality for money or categorizing features to employ in blends. We are also looking for features that may be salient in cocktails because we can match the degree of dilution. When we want to present our spirits to end consumers, we likely will prefer ABV’s in the range of 43-50%.

Something on our appraisal checklist is any blending affinities we can predict. Affinities for rum are fairly wide open, but what seems to close them off the quickest is overly salient oak. I’m not sure if we can call this a rule of thumb yet, but increasing the ester content of spirits with appreciable oak enflames the dense aroma in a jarring way that is not congruent.

Another thing on our checklist is recognizing fruit character beyond generic ethyl acetate. Our best case is finding ethyl butrate, but at the moment it is an open question if it will appear as obvious pineapple character or may feel more concentrated like a Sauternes dessert wine. A cursory glance at common rums on the market shows that vesouté character is fairly uncommon and not necessarily a feature of all non-molasses rums.

Outliers appear like Batavia Arrack. This rum may have appreciable rum oil as an asset but lacks significant esters hence no obvious fruitiness when diluted to 30%. Why is this strange stuff so prized? Why is it so enjoyable in cocktails if it brings no fruitiness? Arrack may contain half the equation of radiance and simply be looking for features to illuminate. In a cocktail, this would be fruit from citrus & liqueurs while in another rum, this may be esters brought to it in a blend.

The 30% ABV white bubble test is a powerful tool, but how widely practiced is it currently? The smartest distillers know it and use it, but is it formally present in your own organoleptic appraisal routine? Bartenders have served tons of it to crusty old blended scotch drinkers, but do they ever practice it when they become buyers and sit down with sales reps? There are countless spirit reviewers, but what tasting techniques are common to their circles? Tons of spirits get appraised for medals in competitions, but what techniques do judges use besides straight tasting?

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Castillo Silver—Fairly neutral, subtle imprecise character. Wide open affinities. Softness on palate.
Alleyne Arthur Barbados—Pleasant generic fruitiness. No overbearing wood. Wide open affinities. Softness on palate. No particular increase in aroma when heated.
João Monteiro Grogue—Penetrating vesouté character. Focused, more narrow generic fruitiness, different than ethyl acetate. Softness on palate.
Weberhäus Rota 48 Cachaça—Almost a grain-like note. Subtle generic fruitiness, probably nothing beyond ethyl acetate. No vesouté. Wide open affinities.
Clairin Le Rocher—Less fruitiness than expected. Non-culinary character. Fascinating to compare to the undiluted sample. No vesouté. Wide open affinities. Capable of adding intrigue?
R.L. Seale 10 year—Soft, but seems dominated by wood. Far less fruity than anticipated. Narrow affinities?
Batavia Arrack—Lacks fruitiness. Soft. Smoke adjacent aroma? Rum oil, no esters? Possible fusel oil. Wide open affinities.
Smith & Cross—Fruity, lovely, many color tones come to mind for the fruit. Soft. Radiant?
Hamilton Jamaica gold—Really impressive. Fruitiness, but evident acidity and structure. Persistence. Fruitiness beyond ethyl acetate. Wide open affinities.
Hamilton Jamaica black—Less structured than the gold. Softer than the gold. Possible sugar? Good but technically inferior to the gold?
Hampden 8 year—Fruit is pineapple-esque; absolute prototype of Jamaica rum. Definitely more to the fruit than ethyl acetate. Structure from possible acidity. Radiance. Retains a unique kind of power and identity upon dilution relative to other rums.
Line 44 New Zealand (unaged)—Extremely unique. Power like Hampden but all the fruit notes differ. Radiance and structure from potential acidity.
Dr. Bird—Exuberant estery aroma beyond just ethyl acetate. Nothing obviously pineapple. No obvious radiance like Hampden 8 or Line 44. Fairly soft, no real structure that may imply acidity. Supposedly this is an oloroso cask finish, but no cask effect is salient.
Demian Argentina—No obvious fruitiness. Barrel aroma becomes elevated by dilution. Rum oil related aroma such as TDN/TNN, not damascenone? Limited affinities due to oak. Congruent with R.L. Seale 10? May add nuance & persistence to a blend.

*After tasting the Hampden 8 year and Line 44 New Zealand rum side by side, the next day there was dramatically more residual aroma in the Line 44 glass. This is where you can get more information by a quick segue to the evaporation test where roughly 1.0 ml that clings to the glass is left behind to slowly evaporate. The degree of aroma that remains implies the magnitude of low volatility high value aroma.

*Some of the “structure” I noticed in a few rums has me interested in titrating the free acidity of the rums. I like this quality in the rum and find it may be a better alternative than barrel tannin. I have already looked at a few of these rums with the birectifier, but I am curious about the Dr. Bird.

The first blending sketch I tried involved exploring spirits that may have limited affinities because of their oak. I wasn’t looking to increase esters in any way. I was looking to increase persistence and intrigue and possibly even dilute some of the oak character to a level that matched my own tastes. I was really liking the character I got when Clairin Rocher was diluted. In the final blend, I was getting an attractive butterscotchy note that really complemented the oak tone. Both Demian and Batavia Arrack where increasing persistence and no doubt nuance because of their differing types of rum oil. I only vatted this at 100 ml, but I wouldn’t hesitate to make more.

Each blending component is so close in price that my next step of exploring this blend may be performing exclusion tests to understand the contribution of each minor component and then figuring out if any component is justified increasing beyond the others. It may also be worth experiencing each minor component increased together to dial up overall intensity—as slight as from 10% to 12%.

R.L. Seale 10 year did not have the highest exhaustive test score, but with this blend, where have we ended up?

Blend	mL/100 mL	ABV	ABV Unit	Bottle Size mL	Bottle Cost	Cost / mL	Cost / Ounce	Cost 1000 ml Blend	Cost 750 ml Blend
Demian Argentina	10	58.77%	5.877	750	$50.00	$0.07	$1.97	$6.67	$5.00
Clairin Rocher	10	49.50%	4.95	750	$38.99	$0.05	$1.54	$5.20	$3.90
Batavia Arrack	10	50.00%	5	750	$34.00	$0.05	$1.34	$4.53	$3.40
R.L. Seale 10	70	43.00%	30.1	750	$33.00	$0.04	$1.30	$30.80	$23.10
Sum	100		45.927	<<-AVE ABV				$47.20	$35.40

**The point of presenting different costs here, such as cost per liter or 750, is to give buyers an idea of costs relative to bench marks they are used to seeing in their market.

The last column here is the exhaustive test score which is our quantitative tasting index of persistence:

Clairin Le Rocher	$38.99	750 ml	49.50%	1:125
Rota 48 Cachaca	$20.99	1000 ml	40.00%	1:100
R.L. Seale 10 year	$32.99	750 ml	43.00%	1:150
Hamilton Jamaica gold	$29.99	750 ml	46.50%	1:200
Hamilton Jamaica Black	$29.99	750 ml	46.50%	1:225
Hampden 8 year	$69.99	750 ml	46.00%	1:275
Smith & Cross	$32.99	750 ml	57.00%	1:200
Dr. Bird	$34.99	750 ml	50.00%	1:375
Batavia Arrack	$34.99	750 ml	50.00%	1:250
Alleyne Arthur Barbados	$12.99	750 ml	43.00%	1:100
João Monteiro Grogue	$24.99	750 ml	40.00%	1:100
Castillo Silver	$10.99	1000 ml	40.00%	1:75
Demian	???	750 ml	58.77%	1:300