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[Sets are not yet available as a package, but you can finally order any of 6 different bubbles. Tasting rooms have been buying multiple for classes and that may create short lead times.
White, 60 proof
Green, 80 proof
Yellow, 86 proof
Blue, 94 proof
Red, 100 proof
Black, British proof
These have been calibrated at 60°F which matches my hydrometers. I’m beginning to think its practical to switch calibration to 70°F for modern room temperature. If the white bubble is calibrated for 60°F, but used in a 70°F room, it would be off by 2.21% ABV (4.42 proof!). The bubble is still useful because you typically just want to use it to create apples-to-apples comparisons between small volume samples. However, if you want to use the blue bubble to explore a spirit at 94 proof, you’d be over diluting down to roughly 88 proof.]
Out of the blue, I’ve got a new product available. These were invented in 1757 by Scotsman Dr. Alexander Wilson (1714-1786) and have gone by many names. They may be referred to as hydrostatic bubbles, spirit bubbles, spirit beads, gravity beads, aerometrical beads, hydrometer beads or even philosophical bubbles. Glass bubbles & beads!
Besides being incredibly rare, with few surviving examples, they were thought kind of obsolete, until you consider them from a few angles and they become very useful. We’ll get to that.
Spirit beads are like a hydrometer but calibrated to a single density measure instead of having a large range on a stem. You put one in your liquid and if it sinks, the spirit is higher ABV than your bead number, and if it floats, it is lower ABV. When the match is perfect, the bead neither floats nor sinks but stays suspended. Under certain conditions this can be more accurate than a typical hydrometer and sometimes test vials were warmed in the hand to dilate so a subtle temperature change made the bead sink; they can respond to changes in tenths of a percent. You have strong visual queues for minute changes as opposed to a measure against the meniscus of a typical hydrometer stem.
As an analogy, high precision machinists use both micrometers and gauge pins. Micrometers are like hydrometers and can handle a range of measures. Spirit beads are like gauge pins and sometimes they are just what you need. They can be either more accurate or give more confidence; go or no−go. They can fit in tight spaces.
Beads for the spirits industry were typically sold in sets of 12 chosen by the user from 40 options. A distiller may choose one set of numbers correlating to their production while a merchant buyer may choose another matching their evaluation and blending needs. Bead number #25 was proof and the higher numbers were for under proofs and the lower numbers for over proofs. Some alternate numbering systems were used that told a blender how much water per gallon to add to bring a spirit to their chosen level. Some sets even existed where there were multiple beads of the same proof but at different temperature calibrations.
Wray (that Wray) in 1844, remarked that there were London bubbles and Scottish bubbles and their numbers didn’t exactly match. He didn’t like the accuracy of his set and adjusted them himself, either adding glass or removing it. He tells us that spirit beads were preferred in the West Indies because hydrometers were too expensive. If you travel the world (without bubble wrap!), spirit beads made sense. If you broke your hydrometer, all was lost and could not be repaired. If you broke a bubble, it could either be repaired or you would extrapolate from the rest of your set. They were & are relatively rugged.
Spirit bubble use persisted through the 19th century into the very early 20th (though there may not have been any producers making them in the 20th). Distillers used them on continuous stills in locked sight glasses where a typical hydrometer could not be floated. Buyers continued to use them to water spirits to traditional levels of appraisal and this is still their strength.
Today, these tools may be enduringly relevant to experimental distillers dealing with volumes too small for a typical hydrometer and buyers & connoisseurs wanting to proof down spirits directly in their tasting glass. The third relevance is that they are simply a fun historical talking point on a tour. If you have a spirit safe, and it floats a hydrometer, add a few spirit bubbles and simply talk about them. So we have a tool that deserves to exist!
My contribution to this art is a useful reproduction that adds a splash of color to differentiate the beads. I also abandoned the old numbering systems in favor of either American proof or ABV. You can also buy single beads because most people only want to cut their overproof spirits down to their favorite drinking proof.
Producing these is not easy because the bubbles need to be blown to a precision tolerance or the buoyancy is not in the range of a practical stem. Using them with no color coding was a challenge because the etching gets hard to make out once they are wet. Adding color was tricky but worth it because it becomes easier to navigate a set or not lose them in a graduated cylinder or glass.
Calibrating these was pragmatic and cannot meet regulatory needs, but can meet anyone’s reasonable needs for distillery & tasting room tasks. I created a series of reference liquids and I check them with narrow range hydrometers before I proceed to calibrate. The bubble stems are continuously sanded on a diamond lapping plate until the correct buoyancy is reached. If like Wray, you remove too much glass, you go back to the torch, add glass, then start over. Half the production time is glass blowing while the other half is tedious calibration.
Shipping at the moment is only within the U.S. Price is $20 per bead and shipping is $5 which can easily be combined for multiple beads.
Appendix of information on spirit bubbles:
Powerhouse Collection example.
The spirit of the age by The spirit of the age, 23 JUL 2018.
Few complete sets exist outside museums. I have one of them. The above examples use a little mercury for ballast. Some were etched with diamonds while others painted numbers on with lead based enamels that were resistant to high ethanol concentrations. Mine are vegan; no lead, no mercury.
Two sets from A. Marnony are in the Irish National Inventory of Historic Scientific Instruments.
John Galletti offered a set calibrated to 80°F which was likely destined for the West Indies. Does Hampden still have any kicking around?
Charles Aiano offered a variant. The odd “s” that looks like an “f” makes me think that these are a particularly old example.
The Thermometer makers of London prepare small glass bubbles, like beads, but hermetically sealed, and formed of different weights, so that, while some will float upon the ordinary brandy of commerce, others will sink in it; and the specific gravities of these bubbles having been ascertained, are marked upon them respectively, by means of a diamond, and they thus become very useful instruments for trying the comparative goodness of spirits; for if a bubble be found which will just sink beneath the surface of good brandy, it will sink to the bottom of that which is still stronger, and float upon the surface of that which is not so strong. The figures 5, 10, 15, &c. marked upon these bubbles indicate per centage strengths, as in the hydrometer, but are not so much to be depended upon, unless used with a thermometer at the temperature at which they were originally formed. They answer, however, very well for the cursory examination of spirits, as above hinted at.
Spirit Gravity Beads are small light hollow spheres made of white or coloured glass about half an inch in diameter, with a stem or tail of about a quarter of an inch in length. The use of this stem is for adjusting each bead to a certain degree of Specific Gravity, or to a given degree of Sike’s Hydrometer Scale. The degrees are engraved upon each Bead, thus forming them into rough Hydrometers for ascertaining the Gravity of various Fluids or Spirits. When the Bead floats about half way in any sample of liquid to be tested, the density or specific gravity of such liquid is indicated by the figures or numbers engraved upon the bubble.
16. Dr. Wilson’s Hydrometer with Glass Beads.
The late Dr. Wilson, professor of astronomy in university of Glasgow, proposed to measure the specific gravities of fluids by a series of small glass beads, or hollow balls, differing from each other in specific gravity. When any of the beads are thrown into the fluid, all those that are heavier than the fluid sink to the bottom, while those that are lighter float upon the surface. By holding the vessel either in the warm hand, or near a fire or candle, the fluid will dilate, and one of glass beads will sink. Hence it follows, that the specific gravity of this bead, which is marked upon it, was either equal to, or a little less than that of the fluid the heat was applied. If any of the beads should happen to be broken, the specific gravity of the liquor may be determined by the other beads; for the liquor which No. 4 sinks will also allow No. 2 to sink by heating it a few degrees, so that No. 3 may be dispensed with. Complete sets of these bubbles, with a small treatise pointing out the method of using them, were made by Mr. Brown, an artist in Glasgow, and have been pretty generally used by spirit−dealers. In some of these sets, the numbers upon each bead are the number of gallons of proof spirits contained in 100 gallons of the liquor; while in other sets, the number expresses the gallons of water which will make a liquor of that strength, if added to 14 gallons of alcohol.
17 Lovi’s Patent Areometrical Beads
The patent areometrical beads have been brought to a very high degree of perfection by Mrs. Lovi. They are now used by many of the first distillers and practical chemists and have been honoured with the highest approbation of some of the principal philosophers and chemists in Scotland. The patent beads are fitted up in boxes, containing different quantities, according to the purposes for which they are wanted, and they are always numbered to every two units in the 3rd place of specific gravity; for example, 920, 922, 924, &c. If they are required merely for spirituous liquors, thirty beads will be sufficient; but if they are required for all fluids, from ether to the most concentrated sulphuric acid, three hundred at least will be required. As these beads are marked with their respective specific gravities, we have only to throw a parcel of them into the fluid till we find the one that stands in the middle of the liquid without either rising to the top or sinking to the bottom. The number marked upon this bead will indicate the specific gravity of the fluid. The beads are accompanied by a sliding rule and a thermometer for making the corrections for differences of temperature, and for finding the strength of the spirits, in the language of spirit dealers and excise officers. The superiority of this hydrometer to every other instrument with which we are acquainted, is very great. If the ordinary hydrometer meets with any accident, it is incapable of being repaired; but if any of the areometrical beads are broken, they can easily be replaced, and the specific gravity may be determined with sufficient accuracy, if one or even two beads of the series are destroyed.
The areometrical beads have been applied with great success by Mr. Hutton to an improved method of ascertaining the quantity of spirituous liquors by weighing instead of measuring them.
A seven bubble set, and these were described as nearly 3/4″ inch in diameter:
18 bubble set by Baldy Bombaly:
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