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Foaming Process Types of Defoamers

Foam Destabilization Mechanisms

Foam Control Agents Available Chemistries

Architectural Coatings

Select Defoamers for Industrial Coatings

When should you add defoamer

How to Evaluate the Efficiency of a Defoamer

How to Evaluate the Efficiency of a Defoamer

There exist several test methods to help the paint formulator to choose the best possible defoamer and know the exact amount needed for formulation. With proper test protocol & techniques, a desired form control agent can be identified for use where the foam is a problem. The selection of a test method to determine the performance of defoamers depends on:

  • Area/surface of use (porous, non-porous...)
  • Application method (brushing, rolling, spraying, printing...)

In many test methods, the foam generation procedure has been developed as a simulation of practical application and both manual and automated methods are used to do this.

Some of the common test methods employed to determine defoamers performance include:

Stirring Test/Density Test - The complete formulation (with/without defoamer) is stirred with a dissolver under defined parameters (time, rotation speed …). After the stirring step, measure directly the density with a density bottle. Best efficiency is the product with the highest density.

Compatibility Test - In compatibilities of defoamer in any given coating system can result in the formation of film defects, such as orange peels, fisheyes, crater, etc. In this test, the paint (with defoamer) is applied with a doctor blade on the glass. After the drying of the paint, a visual comparison with blank sample (without defoamer) is done to measure the influence of the defoamer on gloss, haze and leveling.

Sponge Roller Test - The paint (defined amount, with defoamer) is applied with a sponge roller to a substrate to simulate the paint application on the wall. Micro- and macrofoam can be evaluated on the dried paint film to evaluate the efficiency of defoamer.

A Shake Flask Method - The shake flask test method involves the addition of a certain amount of foaming liquid in the cylinder with plug-in, each time under the same number of shake flask, static observation of foam height and defoaming time.

Other Test Methods - Further depending on the coating systems and end-application requirements, other tests like gloss measurement, volume test, circulation foam tests, etc. can be employed to evaluate the defoaming efficiency.

ASTM D1173 - Standard Test Method for Foaming Properties of Surface-Active Agents [original Ross-Miles method]
This test method covers the determination of the foaming properties of surface-active agents as defined in Terminology D 459. This test method is applicable under limited and controlled conditions but does not necessarily yield information correlating with specific end uses. The Ross-Miles method is used for measuring the foamability of surfactant solutions and the stability of the foam produced, which is based on height measurement.


Source: KRÜSS

This test method covers the determination of the foaming properties of surface-active agents.

Note: There exist several other methods to determine foaming behavior, but they all are not discussed here There are several in-house testing methods being used by material suppliers to obtain qualitative and quantitative results of foam reducing agents.

The results obtained from above mentioned test methods along with surface tension analysis will also help the paint formulator to choose the best possible defoamer and know the exact amount needed for formulation.

What can be done when your defoamer is not performing

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