BMW April 2022

The heat is on!  As the temperatures heat up and as humidity increases, your paint provider in conjunction with your paint shop manager should be making tweaks to your system to compensate for the change in environment. This means altering the speed of the reducers and hardeners used to compensate for the rising temperatures in the paint shop environment. The use and balance of accelerators and other additives should also be reviewed.

When it gets too hot, paint can dry too rapidly and temperatures above 32°C it can cause the bubble to bubble and blister. 

Here are some of the more common identifiers that may indicate there is a temperature problem in your summer system.  

Loss of gloss, blush – Areas of low gloss or a white haze. What causes it? Humidity condenses on the wet paint due to the cooling effect of solvent evaporation when the substrate temperature is below the dew point. Causes:

Unsuitable reducers

Poor air circulation in drying oven

Film thickness too high or low

Only proper humidity control can control this problem. 

Solvent pop – Broken bubbles at the surface of a film that do not flow out during oven cure. What causes solvent pop? When viscosity of the surface of the film increases to a high level, it traps the vaporous solvent at a lower level. The bubbles break the surface when the solvent volatilises.

How can you fix it?

Proper oven staging to enable slow release of solvent.

In an acid catalysed system, use an acid salt to slow the cure and enable solvent release.

Increase flash time before bake.

Use slower evaporating solvent.

For spray application, apply additional thinner coats to build film rather than fewer thick coats.

For waterborne coatings, use a dehydration bake lower than the boiling point of water followed by a second higher bake to cure.

Lastly, the use of lower Tg resins along with lower dry film thickness decrease popping.

Orange peel – Rough surface that resembles the surface profile of an orange. What causes orange peel? Paint applied at high viscosity or under conditions deleterious to proper flow and levelling.

Steps to fix it are:

Adjust paint to proper viscosity with correct reducer per technical data sheets.

Apply at proper fluid delivery rate and atomizing air pressure.

If you are experiencing technical difficulties in your paintshop, contact Allied Paint Solutions (Pty) Ltd