I received an interesting question from a reader:
Dear Kevin/Scotchblog,
I have a simple curiousity about the bottle designs of the various single malts. Particularly, why do most have a similar shape in the neck area with a slight 'bulb'? Is this just a design that developed into a bottle trend or is does it have a technical/scientific reason? Any light you could shed would be helpful. Thank you.
Sincerely,
Scott
I've never come across any mention or discussion of the particular shape of the traditional whisky bottle in any book, so I thought maybe, I'd missed something...
So, I thought I'd ask some of the experts to see if they knew of any concrete reasons for this. Several experts simply said "Beats me." But some others thought they'd take a whack...
Mark Reynier, Managing Director, Bruichladdich Distillery
It was an old bottle design that has become standardised for mass production. Probably, in the past with hand blowing, the neck bulge had something to do with glass strength in the neck of the bottle and for receiving a standardised cork stopper. Today they are produced in moulds.
KME - Bruichladdich does not use the "bulb" - their bottle is very much like the original whisky bottles (see Macallan photo below)
Dr. David Wishart, Author, Whisky Classified gives us this great history of the bottle as well:
The origin of the glass bottle is as a serving vessel, used by the upper classes and by merchants from the mid-18th century. Whisky (and wine) was supplied in a cask or stoneware jar, and was decanted into a clear glass vessel (the decanter, the job being performed by a "bottler", hence the title "butler"). When supplied by a merchant it would be stoppered for transit, with a deposit refundable when returned. Clear glass was taxed at 11 times that of black or green glass, and was therefore the preserve of the wealthy.
The first whisky bottles were re-used wine bottles, e.g. Macallan. They took off in the whisky boom of the 1890s when whisky began being sold by the case for export. They started to be mass produced by glass factories after a glass-blowing machine was invented by Arnall and Howard Ashley in 1887. The bottles were cast in moulds, which presumably followed the style of the decanters used by the upper classes.
The advantage of the sealed bottle for export was that it could be properly stoppered and sealed, thereby reducing the scope for dilution or replacement by unscrupulous intermediaries. During US prohibition, Captain William McCoy, a smuggler based in the Bahamas, supplied such good quality Scotch compared to the illicit bootlegged US alternative, that patrons of Chicago speakeasys dubbed his sealed bottles the "Real McCoy".
As to the shape of the neck, I can only speculate that it evolved from the decanter in a bulbous form for easy and safe gripping by the butler, and has remained that way ever since.
Dominic Roskrow, Editor, Whisky Magazine
I really don’t have a clue beyond to say that if you look at early bottle making, the long neck style seemed to develop out of that early glass-firing process. So you’d assume it was the easiest way of making a pouring bottle - so it’s been imitated as much through tradition as anything else. And of course there are a growing number of different bottle shapes now – suggesting that the science isn’t so important.
Really not sure though...
Dave Robbo Robertson, Easy Drinking Whisky Company
Here are our considered thoughts from our bottling expert.
To be honest, it is a tradition, now widely associated with "traditional" Scotch Whisky design. It probably has resonance in the "bulbous" shape of the pot still. In fact it makes the bottle slightly more difficult to make, not easier, because of the transition of radii. There is a slight advantage in the design in that it allows a little more empty space in the neck (which we call vacuity) thereby allowing a slighly higher fill up the neck, which will look more attractive under the capsule. Not all bottles have a bulb...in fact we have deliberately tried to be different with some of our designs, but a straight neck does look more austere, and more modern I think, and the bulb is softer and more gentle to the eye. Therefore it is more appropriate for older malt whiskies. There is a limit to what you can actually do with a neck!!
Regards,
Mike.
Kevin Erskine, The Scotch Blog
My own SWAG of a guess is that it is a combination of being an easy to hold handle AND having some design function to maximize airflow. I also have a suspicion that the bell shape, mimicked by today's whisky taster glasses, gathers the aroma of the whisky to give you that first great whiff after opening a bottle.
Well there you have it - if there is any real reason for the "bulb" it's been lost over the ages.
Today it's likely just a matter of tradition as many distilleries use the bulbous neck (with wide variations), while just as many do not.
I'd like to thank the experts for taking time out of their day to ponder this question.
And thanks for asking a great question, Scott.
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One of my favorite bulbous neck bottles is used by Balvenie.

Some distillers use the bulbous neck (Glenfarclas, Laphroaig, Talisker)

While some do not (Glenfiddich, Bruichladdich, Oban)

One of the earliest known whisky bottle, an 1841 Macallan. Just a reused wine bottle - no bulbous neck.