James Stanley

On the design of a herb jar lid

Mon 27 June 2016
Tagged: science

My herb jar lid has two operating modes: one has small holes which allow you to shake the herb out slowly, and the other is a single large hole which allows you to shake the herb out quickly.


I am regularly frustrated by this jar because the large hole dumps way too much herb on my food, and the small holes require me to shake the thing for ages.


I set up a little experiment. I emptied the herb into a bowl and had an assistant time how long it took to empty, then I carefully refilled the jar and we did it again, until we had enough results.


Big holeSmall holes
5.3 s560 s
5.4 s-
6.1 s-

You'll notice I only have one result for the "small holes" test. This is because it took nearly 10 minutes and my assistant had had enough. And besides, my arm was tired of shaking.

It takes approximately 100 times as long to get the herb out of the small holes compared to the large holes.


The small holes are way too small. But why is it this way? Does the manufacturer not test the product before they sell it? I have two theories:

1.) The jar is standardised across a range of different herb and was tested against a herb (or possibly even a spice) that comes in smaller pieces.

2.) The jar was designed for this herb, but the ingredients have changed over time (deliberately or not) to favour larger pieces of herb.

I don't know which is more likely. I hope the jar has changed in a few years' time when I need to buy some more, but I am not holding my breath.

Confounding variables

It is likely that the repeated shaking of the herb causes it to break down into smaller pieces and therefore flow slightly faster with each subsequent test. I don't think this invalidates the experiment.

I failed to control for the shaking technique: I tried to shake the herb out as fast as I could each time, but my arm certainly got tired in the "small holes" test. I don't think this invalidates the experiment.

Each time I emptied the jar, I probably lost a little bit of herb. In fact, I certainly left a little bit in the bowl after the first time I emptied it. I don't think this invalidates the experiment.

The herb probably flowed out of the small holes a bit faster at the start than towards the end, because only large pieces were left towards the end. I don't think this invalidates the experiment either.

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