INFORMAÇÃO TÉCNICA


The challenge of micro foam

Foam is the result of air distribution in the coating. Here, gaseous bubbles emerge in the coating or on the coating‘s surface. If foam occurs in the coating container or coating pan, processing problems may be the consequence. This is followed by transfer disturbances or air inclusions in the dried coating layer.
The coated printed product looses gloss and/or scuff resistance. If foam appears in the chambered doctor blade or roller system, a (partial) drying of the coating is possible. Depending on the level of contamination, this may even lead to malfunctions of the printing press. The most usual reason for foaming is the fast pumping of the coating in the container (circulation of coating suction and return flow) and in the printing press.
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Troubleshooting: micro foam in coatings

Solving micro foam in coatings
S​​​​tep by Step

1. Re-position coating suction and return flow

If coating suction and return flow are positioned incorrectly, air can be taken into the coating. Strong foaming is the result. Therefore, install coating suction and return flow deeply below the coating‘s surface on the wall of the container.

2. Reduce the speed of your coating pump

If your coating pump is running too fast, foam may easily be formed. Choose the speed of your coating pump just as high as it is necessary for the coating unit to be filled and emptied properly.

3. Apply defoamer

Defoamers eliminate and prevent foaming. If you add defoamer to your coating, pay attention to the correct dose. Otherwise it may come to an incompatibility between defoamer and coating. The consequence: altered coating characteristics and/or surface disturbances in the dried coating layer. From a container size of 125 kg onwards, we recommend the use of a foam ball. Its purpose is to reduce or eliminate the development of foam if you are using coatings that are particularly prone to foam. It can be applied both with waterbased and UV based coatings. Please contact us.

4. Choose another coating

Many coatings contain raw materials with a foam-building structure. These raw materials determine the foaming behaviour of a coating. Often, they are necessary for the functionality of the coating. A replacement is hardly possible. Please contact your technical representative or use the contact form below.

5. Do you use the correct type of coating pump?

Fast running membrane or rotary pumps can positively influence the occurrence of foam. A peristaltic pump operates in a gentler way.

YOUR SHORT CHECKLIST


Influence factor: Circulation
Measure: Flow line deep under the coating´s surface, return flow just above the same

Influence factor: Pump (1)
Measure: Reduce speed

Influence factor: Troubleshooting
Measure: Apply defoamer

Influence factor: Coating
Measure: Apply apprporiate coating alternative

Influence factor: Pump (2)
Measure: Peristaltic instead of membrane pump

Still have open questions? Contact us and we will support you with the application.

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