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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?


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  • 0
    at the moment the last ice cube melts the water and the ice are both at 0C, assuming well mixed and 1 atm pressure.


    Another method would be to note that lard turns from solid to liquid over the same range, and a spot of that could be used as a gauge. (beef dripping  and suet are a few degrees higher, what you have to hand will depend on your kitchen)

    (animal fats being a blend there is an all solid temp, say 35 degrees, and an all clearly liquid temp, say 45 degrees, and a slushy region in between)

    I presume the hair dye is not for the engineer ?

    regards,

    Mike.

Reply
  • 0
    at the moment the last ice cube melts the water and the ice are both at 0C, assuming well mixed and 1 atm pressure.


    Another method would be to note that lard turns from solid to liquid over the same range, and a spot of that could be used as a gauge. (beef dripping  and suet are a few degrees higher, what you have to hand will depend on your kitchen)

    (animal fats being a blend there is an all solid temp, say 35 degrees, and an all clearly liquid temp, say 45 degrees, and a slushy region in between)

    I presume the hair dye is not for the engineer ?

    regards,

    Mike.

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