How often do you see external factors affect the paint job?
We see it quite often in the industrial realm, since many people use open front paint spray booths, which pull air from the shop environment, or even from outside. This can often introduce contaminants into the paint booth. There are a lot of things to examine, such as the source of intake air and making sure your filters are clean. Replacing your filters on a routine basis, wearing a paint suit, wiping things down, blowing things off and not sanding in the booth are all practices that could help improve the quality of your paint finish.
However, you may run into weird situations occasionally that are out of your control. For instance, a shop once had fisheyes in their clear coat, which started around 10:30 a.m. every day. At the same time, the booth started smelling like fried food. When this shop installed their new paint booth, the exhaust stack was placed on the side of the building that faced a local KFC. Every day, when KFC started their fryers and exhausted the fumes, the shop’s paint booth sucked the fryer fumes into the airflow. If the shop kept the same filters in for more than a month, it would starts to saturate through the filters in the paint booth and ends up on the surface of the item they were painting, resulting in fisheyes. This could have been controlled by regularly changing the filters. It is also a good reminder to be conscious of everything around you, your booth and your shop.