Emissivity / emittance

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Lab test service of emissivity / emittance

We are a Singapore-based third-party test laboratory, providing lab test services of material emissivity / emittance. Our lab is SAC-SINGLAS (ISO 17025) accredited and our customers are from around 30 countries.

Material thermal emissivity/emittance is an important material surface properties determining surface radiative heat transfer rate (What is emissivity?). 

Materials with low emissivity/emittance can effectively reduce its radiative heat exchange with the ambient environment.

Glasses with low-emissivity (low-e) coating can effectively reduce glass U-value. Insulation materials with a thin layer of low-e layer can effectively reduce wall U-value too.

Thermal imaging results are dependent on the material emissivity

Emissivity vs. emittance

Emissivity and emittance are the same and can be used interchangeably.

Emissivity is more commonly used, whereas emittance is more technically correct and in better consistency with similar technical terms, such as transmittance and reflectance.

In test standards, emittance is the preferred standard terminology.

Emissivity / emittance test is a routinely conducted test at OTM. They are part of our standard SRI testing and glass testing service. It is possible to test emissivity / emittance alone. Refer to the information below for more details.

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More information

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Test methods

We use different emittance test methods for general materials and glasses.

For general materials

General materials refer to materials with mixed reflection (i.e. both diffuse and specular reflections). Most materials, except glasses, are general materials. 

  • ASTM C1371-15 Standard test method for determination of emittance of materials near room temperature using portable emissometers
    • With D&S Technical Note 11-2: Model AE1 emittance measurement using a port adaptor, Model AE-ADP

It is possible to measure glass emittance with this method. However, the glass industry prefers a different method, as mentioned below.

For glasses

For glasses, the following method is used.

  • NFRC 301-2020 Standard Test Method for Emittance of Glazing Products
  • EN 12898:2019 Glass in building – Determination of the emissivity

The reason that glasses are treated separately is because that glasses are with specular reflections only (without diffuse reflection). There is a special case for glasses with ceramic frits. They should be treated as general materials, as ceramic frits are with mixed reflection.


Emissometer with small port adapter

For general materials, the instrument used by OTM for emittance measurement is Devices and Services emissometer with scaling digital voltmeter, model AE1 RD1, and small port adapter. The instrument is able to measure surface hemispherical emittance at room temperature.

FTIR with 10 degree specular reflection accessory

For glasses, OTM uses PerkinElmer Spectrum Two with Pike10 10 degree specular reflection accessory. This is also a commonly used instrument in glass testing labs. This instrument measures spectral reflectance of a sample in the wavelength range of 5 micron to 25 micron. The results are used to calculate the emittance of the glass sample.


Most of the time, emissivity / emittance is measured as part of SRI testing or glass testing. Occasionally, we also measure emissivity / emittance along, shown below are some samples.

Aluminium Foil
Ceramic tile

Sample requirements

The test samples to be tested shall be flat (at least in a small patch) and meet the following size requirements:

  • Minimum size: 80 mm x 80 mm
  • Preferred size: 100 mm x 100 mm
  • Maximum size: 300 mm x 300 mm

Only 1 sample is needed and it is optional for the client to provide additional samples as the backup.

For flat sheet type of samples, it is possible to provide us a small roll for us to cut it to smaller size suitable for testing.

Cost, lead time & procedures


Please contact us for the testing fee.

Lead time

The typical lead time is 5 working days.


Our sales personnel will guide you through the necessary procedures.

Upon your request, the following three documents will be emailed to you:

  1. Official quotation
  2. Standard terms & conditions
  3. Test request form

The client needs to return us the following documents:

  1. Official purchase order (PO) or signed quotation
  2. Completed test request form

The client needs to submit the test samples to our laboratory. The test will commerce as soon as possible after the test samples are received.

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