Getting a smooth surface with a Fuji Semi Pro

[Jeff Day]

I picked up a Fuji Semi Pro 2 sprayer over the summer, and I've been struggling to get a smooth semi-gloss finish with SW Emerald Urethane and the standard 1.3mm tip. Despite trying a variety of spray patterns and air levels, I am consistently getting a rough-feeling finish. The semi-gloss look is there, but it feels like 600 grit sandpaper to the touch.

I am adding about 25% water to get the viscosity right, and I'm using the 1.3mm tip that comes with the sprayer. I don't know if it makes a difference, but I have a bottom feed cup rather than gravity fed.

Any ideas what I might be messing up?

[Kevin Jenness]

The product data sheet shows the drying time to touch as 2 hrs @ 77*F. You are probably just getting some dust in the finish as it cures. Try a faster drying material. https://www.sherwin-williams.com/document/PDS/en/035777948088/

[Jim Becker]

My gut tells me that a 1.3mm N/N is too small for such a viscous finish and 25% thinning is too much for a waterborne finish, too. You don't want to thin a waterborne more than 5-10%. Why? Because water isn't the solvent...it's a carrier. Excessive thinning means there is a lot less finish actually hitting the surface and that can lead to appearance and surface issues. For viscous finishes like the Emerald Urethane, ProClassic, Target's EM6500 tinted product, etc., you'll likely need more like a 1.8mm or 2mm N/N unless you're also using the 3M PPS pressure assisted system on your gun. You need to get good atomization for a wet (but not so thick it runs) coat of finish. The rough surface you are experiencing is due to lack of atomization and finish drying before it can flow out.

[John TenEyck]

You have a pressurized cup on your gun so that's good, but you need a larger needle/nozzle set. I use a 1.5 mm with Emerald Urethane and I thin it 10%. It lays down beautifully. However, you may need to add some Extender to it if a larger needle/nozzle alone doesn't fix the problem. Your turbine generates warm air and that can cause the finish to dry too quickly. BM Extender at 3 -5% as part of the water should prevent that from happening. You might even be able to make it work with your 1.3 mm needle. I'd try that before buying a new needle.
John

[Ken Krawford]

I just bought a Fuji system yesterday and the dealer strongly recommended a 1.8 N/N for spraying paints. That's what I used in my old Graco HVLP system and still required some thinning.