The Evaporation Test

[This post is part of a series of background tests that work in conjunction with the birectifier]

The last test that needs tackled before I revisit and integrate all of them is the evaporation test. I did not expect much from this subtle exercise, but was pleasantly surprised. At the bottom of the post on the sulfuric acid test, I provided historic passages on the origins and usage of the evaporation test.

The main feature of the test are little dished watch glass lids that you put over the nosing glasses that hold the sample. They come in many different sizes and have different applications in a lab beyond lids.

In the picture, I experimented with 1.0 mL samples and 0.5 mL samples precisely dosed using my pipetter (I preferred 1.0 mL). What happens is the liquid can still evaporate out from under the watch glass, but very slowly over more than 24 hours which provides time to experience the waves of difference as lower volatility components gradually escape. An extraordinary thing also happens which is that aroma defuses into the head space and can sort of be huffed for a very rich sensory experience from a startlingly small sample.

If this test has little value for analysis relative to the others, it is significantly valuable for spirits tourism. Tourists can be freely given multitudes of samples to experience without getting inebriated or without expense besides that of purchasing and cleaning glassware. These samples can be prepared before hand so they have time to fill the head space.

A big focus on these classic organoleptic tests I’ve been exploring is their wholistic use and integration into tourism. A distillery that expects to have significant front door revenue from tasting rooms and tours, must create immersive engaging experiences. A visitor must be made to feel part of the production and progressive develop of the spirit. You will not find this with the Hewlett Packard spectroscopy black boxes, but only with old fashioned organoleptic assay.

The watch glass based evaporation test should probably be integrated into restaurant trainings and seminars and a host of other applications that would benefit from very rich experiences with very small sample sizes. I have seen this practiced in industry and it would be great to collect observations and anecdotes of its use plus any established protocols that may exist.

With the test, rare olfactory experiences of historical samples can be shared. One ounce, which is 29 ml, can be shared with 29 people. This is certainly not as much fun as drinking something, but in numerous contexts, is practical and useful.

To return to the evaporation aspect, spirits of quality retain very significant amounts of aroma even after they start to evaporate. The rum oil in quality rums becomes apparent through the test, and after the spirit completely evaporates, an oil can be felt with the finger. Spirits aged in newer oak, gain much of the aroma they retain through the wood. After experiencing the test across a broad slice of spirits, a disdain for the ordinariness of oak may develop as well as an appreciation for unique divine character attributed to carefully involved fermentations. Rum oil+ evaporations can have aroma that lingers for days and goes from being enigmatically olfactory-sour (possibly from residual long chain fatty acids in the mix) to yielding to aroma like leather or chai and various teas.

[I explored this next idea with the analytic balance but it didn’t give meaningful results.]

The test could possibly be expanded through the idea of fixation which I’ve explored in the past. Samples of equal volume and proof contained in matching nosing glasses could be weighed on the analytical balance to 0.1 mg at which level you can detect changes in density slight enough to measure alcohol percent sub 1.0 percentage points (every 1.0 percentage point change of ABV is about a 0.0016 change in density so confidence in that “tenth” becomes important). The evaporation of the spirits could be compared with the idea that if a spirit contains noble congeners of persistence, like those prized in perfumology, it will evaporate slower. Those congeners should have a fixative ability to hold on to water and ethanol and prevent evaporation relatively. This may open up questions about added sugar which has fixative properties. Could added sugar meaningfully benefit fixation in a spirit, and would it actually mean anything, or just be an idle observable phenomenon? A balance that can measure a tenth of a milligram is $1400. I’m about to get one and find out. An analytical balance with a pycnometer may also be the most pragmatic of all methods for proofing a spirit which which is a giant distillery challenge/time drain and is another story for another day.

This effort to identify true quality practiced by producers and connoisseurs alike will channel involvement back to yeast selection and fermentation optimization. Connoisseurs will stop obsessing over simple things like added sugar or age statements and start looking for rum oil for their money. This will shake up the industry.