Spraygun Tips

[Daddiojoe]

Going to paint my hood, 4-eye headlight surrounds (both off the truck) and right front fender with Rustoleum-type enamel and HVLP spray gun. In addition to being cheap, figured I might learn something.

It's all primered and sanded--pretty confident about the prep.

Any tips on spraygun use?

Thanks,
Joe

[712edf]

HVLP's require thinner material than conventional cup guns (obviously strain everything). I regularly spray metal using an HVLP (non automotive paint). On the smaller pieces I use the round fan setting on the gun. On larger pieces I use the round fan setting and spray the perimeter/edges first then switch to a regular fan pattern for spraying the larger surface areas. The first coat is a piss coat, very little paint on the surface but keep it uniform. Horizontal pieces are more forgiving than vertical pieces (runs). Between coats I disconnect the gun from the turbine and use the hose to blow warm air over the surface to encourage the paint to tack up a bit before proceeding further.

The type of painting I do isn't as critical as an automotive finish though. Maybe a true auto body sprayman will have more specific & accurate advice.

[Daddiojoe]

Thanks for the tips. Others have said to keep momentum all across the surface, so not just painting an edge but sweeping across the entire panel.

All help is appreciated.

Joe

[712edf]

Also on the HVLP gun usually there is a small hose connecting the top of the cup to the upper part of the gun. On new guns there's not an issue, but as a gun is used this hose tends to get paint in it & becomes clogged. This causes the gun to no longer work properly. This hose must remain clean & unobstructed. The purpose of this hose is too pressurize the cup forcing paint up & out of the cup & into the head of the gun. The is different from conventional cup guns where airflow siphons paint out of the cup.

I use HVLP's in spraying cabinetry, shutters, awnings, doors, vent grills, etc. where the edges tend to need more paint buildup than the rest of the surface.

[Russ]

Get your volume and pattern set up on a piece of news paper or plywood or something else before starting to spray your good pieces. Get familiar with the gun before you spray the first good piece or you might find yourself sanding and starting over. BTDT, lol. (been there,done that)

[712edf]

I agree with Russ, but I'd practice on something non-absorbant like glass, formica, or sheet of plastic taped tight to the wall. This will simulate the metal surface better than paper/wood which would tend to absorb more and not be an accurate representation of what surface type you'll be spraying.

[Daddiojoe]

Success!

I shot last Friday, messed it up, did a lot of sanding and primering, shot again this morning, and it doesn't look too bad.

My main problems:

1. Dusting paint on didn't allow enough coverage for the paint to lay down flay and caused roughness in subsequent layers.

2. Instead of easily visible drips, paint kind of bunched up into a kind of fingerprint texture that took over a week to dry.

I think I avoided both of these problems this time around. Still need to paint my hood.

When painting w/ Rustoleum (old school synthetic enamel):

Be sure to use hardener (only to be found and Tractor Supply stores around here) 1 part hardener to 8 parts paint

Use paint thinner over mineral spirits. Dries quicker.

Over a week and there are places on my hood that are still gummy. Waiting for them to dry before sanding. Did not use enough hardener and used mineral spirits instead of paint thinner.

All w/ a bargain sprayer from China Freight.

Will post pix when it is all done. Thanks for your help,

Joe

[712edf]

Sorry about telling you to go light on first coat, but I figure orange peel is easier to fix than runs/sags. HVLP's tend to "spit" the paint on as opposed to spraying, at least this is true with less expensive versions. Also waiting too long between coats, wrong viscosity, too hot air or surface material, & several other factors contribute to overall smoothness. Like I said I'm a housepainter where the variables don't have to be as precise as in automotive finishes.

mineral spirits is kinda oily, naptha may be a better option. Depends on what the paint manufacturer calls for.

[Daddiojoe]

"Over" mineral spirits should read "instead of" mineral spirits. Yes, no more mineral spirits--paint thinner works better.
Also, I was shooting in TX heat. In the last two weeks there was one day that didn't hit 100 (only 97). So that probably made some difference somewheres.

I got a better mix with the hardener the second time around. Added more so it was 1 to 8 ratio.

JOe