You may notice on Dyne test reports that the test categories are grouped into physical properties and performance properties. Physical properties tested on all foam and premix solution samples include Appearance, Refractive Index (if applicable), pH, Density, and Viscosity (if applicable). The physical properties are not a measurement of performance and will not typically cause a sample to fail, with the exception of extremely low viscosities on AR-AFFF samples and out of spec pH results for foam tested to the International Maritime Organization (IMO) specification. The data provided by the physical properties is very valuable, as it gives information about the quality of the foam and how the foam has changed since first manufactured.

Usually, the physical property specifications are based on the most current published specifications provided by the manufacturer of the specific foam that is being tested. If the brand or type is not known, a generic specification encompassing all of the brands is used. Below is a quick explanation of the physical properties tested at Dyne:

Appearance of the foam includes color and visible presence of particles. If the appearance of the foam differs from newly manufactured foam, it can indicate aging of the foam, a different foam type, rust from piping, or sediment.

Refractive Index is a measurement of the angle in which light bends as it passes through the sample. The refractive index is proportional to the amount of solvent in the sample. (This is why refractive index is used for finding the % concentration in premix solution samples). Density is a measurement of the weight of a specified mass. Density and refractive index can be crucial in giving information about the product. A low density and/or refractive index can indicate dilution, while a high density and/or refractive index can indicate evaporation or contamination or a misidentified type of foam.

Viscosity measures the thickness of a foam. A reduction in the viscosity can be an indication of foam dilution. An increase in viscosity can result from aging. If the viscosity is either above or below its specification, it could prevent accurate proportioning.

Lastly, pH determines the acidity/basicity of the sample. A low pH means the sample is acidic, while a high pH means the sample is basic. A sample that is basic or acidic often indicates corrosion within the tank or degradation of the foam. Replacement is recommended if the pH is outside the 6.0-9.5 range.

After the physical property tests are completed, the sample goes on to performance testing. The performance properties are designed to test the foam's ability to perform effectively in a fire situation. Using both the physical properties and performance testing, the quality of the foam can be assessed. A more detailed explanation of all the testing is available on Dyne’s website, “Foam Testing Explanation LBTR-4054”.

Ensure that you are using the resources available to you at Dyne Technologies. Our staff chemists are ready to answer questions that you may have regarding your test results. Call Dyne at (800) 632-2304 or email,, for assistance with understanding your test results.