Pigmented Precat Problems

Hey all,

First time using pigmented precat and it's been a pita. I'm far from pro but I'd heard SW hi-bild precat was easy to work with and I've sprayed enough things successfully to be foolishly confident that I could use this stuff. Also, never sprayed opaque.

I'm sure part of this is gear, but initially I just could not get a good flow. I'm using a Fuji Semi Pro 2 with a 1.5 tip, air full blast. Once I had it thinned to 30% I was able to get it to coat pretty well, but it seems like this is probably much higher than it should be? Should I be going for an even larger tip?

Second and much more annoying issue, this stuff seems to corn instantly. Just sanding between coats, literally one drag across the surface and the sandpaper is pilled up and just shredding the finish with deeper scratches. I've used everything from 240 through 600 hoping to get a better result with no luck. Wet sanding only seemed to help slightly. Doesn't seem to be related to dry time as I've let it go for several days at times with the same results. With how much I've had the material thinned, it won't cover the scratches left behind by the scuff sanding. My understanding is precat requires sanding between coats, so in theory if I have to sand between each coat and a coat won't cover the scratches from scuff sanding, I'll be spraying this stuff for eternity which I really don't have time for.

Any ideas what I could be doing wrong? Laying it too thick? Too thin? Material too thin? Not thin enough?

Hoping somebody whose worked with it may have a magical answer to save my sanity.

First thing is that tinted pre-cats are always a bit more difficult to work with. You sanding problems are routine. However, you should not need to do more than de-nib after the initial sand of the first coat.

Make sure you go to extra effort to prepare the surface before coating. Less furry bits to deal with helps enormously. This is the rule for all polishing but especially for your coating type.

It sounds like you need to work with your gun set up a bit. Full blast air is not a recommended strategy. Change up to a 2.0 tip so you get some flow. Cut your air back to the minimum that atomises the product and don't be afraid of using thinner. It is important to understand that big tips can be adjusted down to restrict fluid flow but the other way doesn't work. A 2.0 tip will still give you a finish you can use as a shaving mirror.

Thinning 30% is not outrageous. For a first coat, up to 50% is OK if necessary.

This type of product only puts up with minimal sanding as you have found out. Avoid heavy coats as they won't cure quick enough. Much better to apply additional thinner coats. The first coat especially should be thin so that it dries quickly and you don't have much trouble sanding to get rid of the furry grain. After that first sand, you should only need to de-nib after successive coats. This means apply a smooth, just-wet coat so that you avoid orange peel and really cut down on the need for more sanding.

Use 320-400 for sanding. Briefly rub new paper face to face to take the top edge off before using it. Use old, almost dead paper for later stage sanding. Never apply pressure to the paper. Use a foam sanding block or a cork block with felt glued to the face as a backer for flat areas. The galling is as a result of pressure and friction heat. Cheers

Thank you so much for the detailed reply, feel like I might actually be able to get through this without pulling out all of my hair now.

Small followup, these are all doors/drawer fronts, I've got about half of them done to what seemed decent for me. I was planning on rubbing them out in about a month or so to get rid of whatever little imperfections were left, is that a mistake with this type of material if there's no clearcoat on them? I'm assuming it's the pigment that makes sanding this stuff such a pain, or is it just the nature of precat?

Its both. Pre cat is not the greatest to sand at the best of times but pigmented versions are a bit worse. Higher gloss is worse than lower gloss as well.

You should expect to get a good finish straight off the gun. Pre cats work best if done over 2 days. First coat day 1, leave over night, sand, 2nd coat, dry for a while then de-nib and apply final coat. Repeat the last 2 steps if you want a fuller finish. Cheers