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Encaustic Infrared thermometer ( thermometers for measuring encaustic temperature properly said) are not the best option and we are going to explain you why.

Remote thermometers have recently appeared in the consumer market at a very affordable price. They are thermometers based on the optical technology of detection of infrared rays. These thermometers measure infrared radiation emitted by materials that are above zero degrees Kelvin (0 ° Kelvin = -273 ° C). Depending on the energy emitted by the object and received by the “optical detector” of the device, the electronics calculates the temperature of the object.

What you need to know

The temperature obtained is affected by some important factors:

Emissivity of the material

The temperature of an object is proportional to the ability of the materials to emit heat. Emmitting more or less heat depends basically on a characteristic that is called “emissivity”. The most common materials have a high emissivity coefficient, close to 0.95, and this is the coefficient with which the electronics of the “simple” infrared thermometer calculates the temperature (with the formula of the Stefan-Bolzman’s law of black body radiation).

But there are many other materials with very different coefficients of emissivity, we give some examples:

Beeswax – 0,9
Paper – 0.93
Oil Painting 0.92
Oak wood – 0,89
Anodized aluminium- 0,77
Gray steel – 0.30-0.50
Cement – 0,54
Tin – 0,04
Gold Polished – 0,025

“Professional” infrared thermometers can be calibrated for different emissivity coefficients depending on the material. The simplest ones give inadmissible errors on metallic surfaces.

Measurement field (or optical resolution)


The laser you see when firing your device has nothing to do with the surface you are measuring. The laser serves only as a guide so you  approximately know where you are pointing to.

The surface where you measure depends on the distance at which you measure, the further you measure, the more surface you are measuring. To know exactly how much surface area you are measuring, you have to know the optical resolution (ratio between distance and diameter), information that usually comes in the specifications. A ratio 1: 1 for example means that at one meter, the surface you measure has a diameter of one meter.  Ideally the surface to be measured should be twice as large as the measurement field.


The encaustic infrared thermometer  is not the best option to measure temperatures of the palette or the wax. They poorly measure the temperature of metal surfaces and do not measure the internal temperature of the molten wax at all.

The best option to control the temperature of the plates where we melt the colors are the contact thermometers, as they accurately measure the temperature of the surface. To heat the medium the best option is to use double-chamber saucepans type “water bath”.
But … if you already have an infrared thermometer for encaustic:

Encaustic Infrared thermometer

If you have bought an infrared thermometer for encaustic that can not be calibrated, it will be very difficult to really measure the temperature of your palette but we can give you five tips:

  • Look at the specifications manual or on the internet. You have to find out the emissivity for which it is built and its optical resolution.
  • Make sure the surface you want to measure is wide enough and even.
  • Measure from a small distance so that the surface you are measuring remains small. Try to measure perpendicular to the surface and be careful that the lens is always clean.
  • If your encaustic infrared thermometer has no possibility to calibrate the emissivity, you can do a quick calculation according to the coefficient of emissivity of the material.

You  have to multiply the temperature that the infrared thermometer gives you  by the coefficient resulting from dividing the emissivity of calculation between the emissivity of the material in question,…t is easier than it seems… An example: Your thermometer is calibrated for 0.95 emissivity (see device specifications) and you are measuring a gray steel surface (0.3), then 0.95 / 0.3 = 3, the actual temperature is obtained by multiplying by 3 the temperature of the thermometer.

If you measure the surface temperature of a metal, you can put a piece of insulating tape (better black).  Caution! The tape should cover the entire focused area. Be careful it does not burn!

  • When measuring, you have to remove any device that creates magnetic fields such as induction plates, remove also any other  hot objects nearby.

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This post is also available in: Spanish