Jiggers or measures are used to portion control alcohol for consistency, compliance and long term profitability!
Now here’s an interesting question: Why are jiggers round?
Could it be that our design ancestors may have got it: Wrong Way Round!
Let’s take a look.
Why round jiggers?
Round jiggers when filled to the top create a lens or dome called a meniscus. There’s no magic to why this happens, it’s just a question of physics or surface tension.
The meniscus adds approximately 10-15% more to a measured liquids total volume, over and above the designated volume marking shown on the side of the jigger... i.e. 30 mL or 1 Oz etc.
Here are some internationally popular volume serves, with the arising meniscus consequences:
20 mL plus 10-15% 2.0 - 3 mL
25 mL plus 10-15% 2.5 - 3.75 mL
30 mL plus 10-15% 3.0 - 4.5 mL
1 Oz plus 10-15% 1/10 - 1/6 Oz (approx.)
Now we know what the meniscus looks like so how can we measure it?
First you’ll need a volumetric scale. We used a scale accurate to
1/1000 of 1 mL or 1/333 of 1 Oz. If you have scales with a digital read out and tare facility then you too should be able to replicate the results (email: firstname.lastname@example.org to ask for the testing process).
We have used a standard 30 mL egg cup jigger to test as it happens to be see through and easier to see the meniscus and arising issues, however as all jiggers are round it really makes no difference as to which one you use. If you try this test on a number of different jiggers you’ll be horrified by the massive range of volume variations!
The before and after pictures above show a 30 mL /1 Oz jigger on the LHS with the meniscus formed at the top. Note: Mils (mL) and Oz are almost identical 30 mL = 29.57 (1 US Fluid Oz).
Note the RHS picture shows the same filled jigger pictured standing further back so we can see the digital read out. The numbers reflect the weight of the liquid inclusive of the meniscus with the actual weight of the plastic jigger zeroed out. 1 mL =1 grm in volume is the same in volumetric weight. In the case above 34.6 mL = 34.6 grm.
Now to work out the weight or volume of the meniscus, in this case 4.6 mL
deduct the read out from the designated volume shown on the side of the jigger (34.6 - 30.0 mL = 4.6 mL).
To work out what the percentage over-serve “measure” is, divide the over-served volume amount and divide by the designated volume i.e. 4.6mL /30 mL to get a figure of 15.33%, over-serve.
The same story would play out percentage wise if we used a 1 Oz, 20 mL,
25 mL or 2 Oz jigger.
What can be done, to solve?
Based on figures of 10-15% over-serve on almost every jigger pour, it’s not very hard to see the cumulative cost to a bar or restaurant business.
An example of what the cost to a business is of the over-served meniscus, let’s do some more math.
Say a bar sells 5 cases of spirits a week… equivalent to 60 bottles of 700 mL spirits. Assuming a shot of alcohol contains 30 mL.
1 bottle contains 700 mL of alcohol divided by 30 mL (the volume of 1 shot) to calculate the max amount of shots can be served from one bottle; answer 23.33 serves.
60 bottles X 23.33 serves = 1400 shots maximum can be served
So what’s the loss per week/pa :
A 10% meniscus loss equals 140 shots lost (1400 X 10%) 7280/pa (x52)
A 15% meniscus loss equals 210 shots lost (1400 x 15%) 10920/pa (x52)
So whilst history is cool, round jiggers we can see are somewhat of an anomaly.
Based on what we now know with science and the needs to save money/generate profits, it appears that when it comes to round jiggers history definitely got it: Wrong Way Round!