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Interesting problem ... basic engineering solution

gkenyon
So, today's engineering problem goes like this.


Someone in our family is dying their hair. The chemical (probably a Chromate-based hair dye) must be mixed with 180 ml of water at between 40 and 50 °C - if the temperature is too low, mixing is very difficult, too high and the compound breaks down, and perhaps you might not get the hair colour you need.


Simples ... except we have no thermometer.


How was this quick and easy to resolve?


Parents
  • 0
    I can confirm Graham's thoughts about the cold water temperature in summer.


    I had similar problems developing films (if anyone remembers cameras that don't plug into the computer or make phone calls.....) as the temperature of the chemicals for developing them had to be 20 degrees Celsius. If mixed and they were too warm it was a b***** to wait until they cooled down so the proportions of water from the cold and the hot tap were critical. The cold could be anywhere between about 5-10 degrees in winter (cold water tank in the attic still got that cold in winter despite the central heating in the main house) to very close to 20 degrees in the summer when adding any hot water could put the temperature too high.
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  • 0
    I can confirm Graham's thoughts about the cold water temperature in summer.


    I had similar problems developing films (if anyone remembers cameras that don't plug into the computer or make phone calls.....) as the temperature of the chemicals for developing them had to be 20 degrees Celsius. If mixed and they were too warm it was a b***** to wait until they cooled down so the proportions of water from the cold and the hot tap were critical. The cold could be anywhere between about 5-10 degrees in winter (cold water tank in the attic still got that cold in winter despite the central heating in the main house) to very close to 20 degrees in the summer when adding any hot water could put the temperature too high.
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