Hard to Get Smooth Finish from Spray Cans?

[Chips O'Toole]

I made myself a tool chest attachment to hold belt grinder tool arms, and then I tried to paint it. I used Rust-Oleum primer and farm implement paint in spray cans.

On the first try, the paint came out rough. I started wet-sanding it so I could spray it again, and I found a bunch of surface imperfections in the paint and metal, so I stripped it with an angle grinder and started over. I painted a small area that won't be very visible. The paint still looks rough.

Should I give up on spray cans? I've gotten beautiful, glossy results from the brush version, but it's not much fun to apply. Does anyone else here get smooth finishes from spray cans?

I held the can at the proper distance from the work while spraying, so that's not the problem. The humidity is very high this week. I don't know if that causes problems.

 

[neonguy]

Hi humidity can cause some paints to start to "dry" as they are still airborne. You may get better results on a drier day. Also, if the paint can has been exposed to freezing, or near freezing temperatures, I have had it produce a rough finish. Normally spray cans should produce a very smooth finish. Good luck.

 

[Ulma Doctor]

i often warm my paint cans in the sun before use.
i never have much problem unless it's too cold or i didn't prep well enough

 

[Chips O'Toole]

The humidity isn't that bad today. Only 97%.

 

[great white]

The humidity isn't that bad today. Only 97%.

Yep, that’ll do it.

To spray, you want hunidty down in the 55-60% or lower range. Much higher than that and spray paint can get water infused in it from just the air and result in anything fron a hazy look to roughness or poor adhesion.

 

[Chips O'Toole]

I can't spray this thing in the house. Maybe I can use brush paint on it and bring it inside to dry. That will smell lovely.

Tomorrow will be really dry and brisk. Only 88 degrees and 63% humidity.

 

[woodchucker]

I made myself a tool chest attachment to hold belt grinder tool arms, and then I tried to paint it. I used Rust-Oleum primer and farm implement paint in spray cans.

On the first try, the paint came out rough. I started wet-sanding it so I could spray it again, and I found a bunch of surface imperfections in the paint and metal, so I stripped it with an angle grinder and started over. I painted a small area that won't be very visible. The paint still looks rough.

Should I give up on spray cans? I've gotten beautiful, glossy results from the brush version, but it's not much fun to apply. Does anyone else here get smooth finishes from spray cans?

I held the can at the proper distance from the work while spraying, so that's not the problem. The humidity is very high this week. I don't know if that causes problems.

yep, it's not hard.
hard to tell what you are doing wrong.

I prefer to spray using a compressor and HVLP conversion guns. I switched from siphon to gravity, it's a game changer. you can get away with more, plus they don't spit when they are running low like a siphon can. Gave up my good binks guns.
I also have an early HVLP / w/turbine. Not as much a fan as the compressor.

So first, it sounds like you had a problem from the get go. Rough.. so I won't talk about time between coats.
Was your primer sanded smooth? If not, your primer will print through, so an unsanded primer will look like a rough finish.

If you are spraying outside, you will get orange peel in windy weather with lacquers, not so much with rustoleum enamel, but I'm throwing it out there.

Are you spraying too close, or too far? Too far is better than too close. The coat will be drier and require more coats, but thinner coats are always better than too heavy super wet coats. If you are really good you can get away with wetter coats, it's a matter of knowing how fast to move and how to prevent overloading the coat.

Was the can stored inside in air conditioning or cool basement and then taken outside? That's not a good idea. The paint being warmer is better than being cooler. If spraying a can in cold weather (I know it's not now) I put the can in hot water to allow me to mix it better and get a good rattle. It also allows the spray to be a finer mist, cool paint does not atomize as well.

I'll add to this as I think of possible things you might have done wrong, or things you might be running into.

 

[markba633csi]

Spray can paints tend to put down a thinner coat than brush. Sometimes you have to load it on pretty wet to get a smoother result, but not so heavy that it drips- it's a fine line. Rustoleum is pretty forgiving. I like the "Industrial Choice" line of their paints
The humidity would certainly be a problem for any kind of spray painting
-Mark

 

[Chips O'Toole]

I didn't sand the primer because I haven't had this problem until now. I didn't sand primer coats in the past, and I got good results, so I didn't see this coming.

The cans were stored in the workshop, which is hot.

I tried to stay about 10" off the surface.

I'll say this: using the angle grinder to strip the paint off made the project look a whole lot better. Paint made a bunch of welding BB's and surface imperfections stand out, and the stripper disk really ripped that stuff off.

I used these Chinese jobs. At the time I bought them, they were way cheaper than Nortons. Now Nortons are cheaper. Maybe they moved to China!

https://www.amazon.com/gp/product/B08DD1L2MP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Dhal22]

Yes on lower humidity but not too low as the paint needs time to flow. 50-60% is correct. Then only a light pass, come back 30-60 minutes later with another light pass, then another. At that point might as well clear coat it..........