Phase Change: Labels, Paints, Crayons, etc.

Phase change temperature measurement devices or thermometers take many forms and are familiar to lots of people in industry and commerce. They are found in forms like temperature labels or temperature stickers having a central white or yellowish dot that turns black when the temperature value printed on the label is exceeded.

They are single use devices although they may have multiple points on a single label.

Crayon and Paint “Thermometers”

There are also temperature or thermal paints that change color and temperature crayons that melt and become liquid when their specified temperatures are exceeded.

Also, the thermal paint devices are used only once., but the crayons can be reapplied due to the simple nature of their use.

There are lots of them and they are relatively inexpensive. The major uses are where a quick check of the temperature of an object is desired, or, in the case of the temperature labels or stickers, a record of whether the object has exceeded a certain temperature.

This latter use provides many industrial temperature-sensitive instruments and apparatus a valid check as to whether maximum temperature ratings covered by warranty have been met or exceeded.

Check the links below to the various sources of information on phase change devices.
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  • Phase Change Thermometers are available in many different sizes, shapes and temperature values. The ones of most use to testing staffs are the sets of labels that are offered by many vendors. Ranges are limited to about
  • Typical Maker’s Tolerances are: ±1 % of Temperature
  • Standards
  • Phase Change Thermometer Vendors
  • Miscellaneous Information
  • Phase Change Thermometer Applications

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