On Monday, 26 December 2016 16:32:25 UTC, Bernard Burton wrote:
"Vidcapper" wrote in message
...
On 26/12/2016 11:31, Desperate Dan wrote:

Met office mercury in glass thermometers have a five year calibration
period.


Why just 5 years - surely the only thing that can go wrong is if you drop
them?

--

Paul Hyett, Cheltenham

Not so. The glass can creep due to changes in the glass of the bulb, which
contracts slowly over time.

--
Bernard Burton

Satellite images and weather data for Wokingham at:
www.woksat.info/wwp.html



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Mercury thermometers can be fairly accurately home-calibrated using a bucketful of partly melted slush. Use as large a volume as possible and stir it for a long time but make sure there is ice present. The maximum thermometer will have to be stuck in the fridge, rapidly shaken down and placed in the bucket and the maximum temperature read. The amount of dissolved solid even in the hardest water is so small that the melting point will not be materially lowered. I've done this with every thermometer I've had. Slush, not available as a natural product these days, can be obtained from the fridge - just let it build up over the weeks.

Tudor Hughes.