I was helping out in the Sales office a while back, and took a call from a customer in Somerset, who was after some clear plastic sheeting. He wanted something to keep some stuff dry that was being kept outside during a prolonged period of wet weather. It wasn’t going to be needed for very long, so I was fairly confident some 100 micron plastic would be sufficient.
“How thick is that?” asked the customer.
You get used to some people using microns as a unit of measurement and others using gauge.
“400 gauge,” I replied.
There was a pregnant pause.
“And how thick is that?” he asked.
Through thick and thin
You may not be aware that the micron has not been an officially recognised unit of measurement since 1967. In that year, the 7th resolution of the 13th meeting of the General Conference on Weights and Measures was meant to consign it to history, along with the ‘new candle’, a measurement of luminous intensity.
Outside in the real world, everyone carried on measuring in microns as if the 13th meeting of the General Conference on Weights and Measures had never happened.
A micron, which we should apparently have been calling a micrometre for the last 45 years, is by definition 1 x 10-6 of a metre. Still in the real world, that’s one millionth of a metre, one thousandth of a millimetre, 0.001mm or 0.000039 inches – whichever makes most sense to you.
One gauge, meanwhile, is 0.000254mm, or 0.00001 inches. Put another way, it’s 0.254 of a micron. So, technically, 100 microns = 393.7 gauge, but what with industry tolerances and tricky mental arithmetic, everyone just multiplies or divides by 4 to convert one to the other.
In the USA, incidentally, they measure plastic in ‘mils’. One mil is 0.001 inches, or one thousandth of an inch.
My measured response
So I could have told my customer that the polythene sheeting I was offering was 0.1mm or 4 thousands of an inch thick. I could have put on my finest American accent and said it was 4 mils. I could equally have said it was the same thickness as the average human hair or a coat of paint. I didn’t, mainly because I didn’t know any of that at the time.
What I did tell him was that it was thick enough for what he wanted to do with it. I must have been convincing because I made the sale and have heard nothing further since. And the moral of the story? Knowledge is all well and good, but sometimes it helps to keep things simple.
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