The air needs to be dirt-free too and a clean environment are required for a flawless paint job on an auto. However, many shop owners installs only a simple coalescing filter and believe they has addressed all their issues. They fail to recognize complex details of compressed air contamination.
Compressed air is not just air. It have oil aerosols, water vapor and particulate matter which need different means of removal. Failure to consider entire spectrum of contaminants will show up as orange peel, craters or fish eyes in your finish.
And more times than not, you’ll attribute these flaws to paint mixing or technique. In reality, the air supply is most likely at fault and proper knowledge of three stage filtration process make the difference between a good finish and a great finish. Why?
How Three Stage Filtration Protects Paint
Why Compressed Air Contamination Matters
It remove the oil, moisture and debris from the air before it get into gun. A pre-filter is coarse sieve that removes heavy water droplets and other large particles like dust and pipe scale. The purpose of this stage are to catch big stuff before it hits your downstream filters.
If you don’t have one, your downstream filter would of clog within hours. And it also protect the expensive media in the later stages from failing too soon. By design, this stage is sacrificial.
It take the beating to ensure the rest of system survives. You’ll know it’s time for a change when you notice dark liquid filling up the sight glass…quickly. Many shops does not regularly maintain this stage, resulting in pressure drops that will ruin your spray.
Remember, a clogged pre-filter restrict airflow. Your spray pattern become inconsistent and uneven.
The Role of the Pre-Filter
The second stage is coalescing filter, built to capture sub-micron particles and oil aerosols.
The real work come in the second stage. What you don’t see with your own eyes, oil vapor from compressor lubricant, is deadly for a paint job. Coalescing filters uses glass fiber media.
This media combine small droplets of oil into larger droplets which is drained away. This prevents fish eyes; those little craters are caused by oil hitting the wet paint and pushing the clear coat away. In order to achieve a good result, you has to go all out at this stage.
A quality coalescing filter lower oil levels below 0.003 ppm and that figure is important as it cause total finish failure at very low levels. To get the professional results you’re looking for, you can’t cut corners here.
Coalescing Filters for Oil Removal
The third stage are polishing the air using what we call an activated carbon filter, which remove odors and oil vapor from the air.
The coalescing filter let gaseous oil pass through while catching any liquid oil. The activated carbon then soaks up those molecules making the air realy clean. This is critical for sensitive clear coat and paints.
Clear coat and paint is susceptible to vapors that can be locked in by solvents. Many painters skips the final step, assuming they are done once all the liquid are out. But there is still vapor residue that can contaminate booth environment.
A carbon filter add a level of insurance and savings in reduced rework costs. It also guarantee that there is never a hint of odor or oily vapor reaching the wet surface.
Activated Carbon Filters for Vapor
Proper installation of these stages is key and half the battle.
The order make a difference too. Carbon goes last. Coalescer go next and pre-filter go first.
It’s backward and shorten the life of filter. Make sure they’re rated for your system pressure and that all the fitting are tight. Nothing can be worse than a leak from these filters as this introduce unfiltered ambient air into the system and negates everything you’ve done.
Don’t change them based off time alone, but rather on how you use them. Busy shops uses up a filter quicker. If you notice liquid building up in sight glass, don’t wait until the indicator turns red to change it.
Steady pressure stabilize your paint guns. It help atomization work right. It also keep your flow consistent with a fresh filter.
Proper Installation and Maintenance
Good filtration costs money but it’s money well spent and people see all of the swirls and specks. If you use a good three stage filtration system the only thing they’re going to know about is your workmanship. No one wants to hear the air was the problem with their finish.
Clean the air, let the work do the talking.
