The past couple of paint grade jobs we've done we've had some problems with Magnaclaw. No matter how I sand this stuff, with anything from 180-320 grit, there is a rough texture visible once I spray topcoat (Magnamax). I know for sure the problem is the primer, as I test sprayed a piece of UV finished plywood and the Magnamax laid down glassy-smooth. The rough texture is not unlike what melamine feels like. I get this on every sheet good: MDF, plywood, hardwood. This problem has happened with the past two 5 gallon cans we've had, but I don't know necessarily that I got two cans of bad primer. I just don't know what's up.
Here's our setup and order we have used for nearly two years and it's worked great:
Titan airless (non-air assist), using a 310 tip.
Spraying the primer 4-7 wet mils, particularly on MDF.
Two primer coats, sanding back hard to fill the grain.
One or two topcoats of Magnamax (one being the norm - this has produced good results in the past but not now).
It just seems like the Magnaclaw just doesn't act like it once did. Is it the heat? Our shop stays in the mid 80's.The only way I have been able to overcome it is to sand the hiney out of the first topcoat and spray a heavy-handed second topcoat.
From contributor A:
It sounds like orange peel - material not flowing out because the coat was too thin or it dried too quickly (summer heat). Have you tried retarder?
The other side of the coin is when pigments settle and clump at the bottoms of containers. You want an even dispersion, and even suspension of pigments. Proper shaking/stirring (only possible with machinery) is what suspensions need.