Painting fender with rattle cans

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  #1  
Old 02-08-15, 08:30 PM
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Painting fender with rattle cans

Hi,

This a follow up to an inquiry I made in Sept 2014. I finally started painting the left front fender on my 92' Ford Ranger. I opted for white gloss acrylic enamel spray paint from rattle cans. I'll probably finish with five coats.

After the third coat dried the finish has a rough, gritty feel to it. Not smooth at all. I can see paint particles. Do I smooth this out with steel wool and/or very fine (400 grit?) sandpaper in any particular order?

And is it ok to use black sandpaper on white paint if I can't find anything else?
 
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  #2  
Old 02-09-15, 04:00 AM
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Yes, use 400 or finer paper (color doesn't matter) to smooth between coats.
 
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Old 02-09-15, 04:08 AM
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How far apart are these coats?

When you apply multiple coats using an enamel paint they need to be done no more than an hour apart or before each coat looses its tackiness.
Enamel paint relys on solvents floating to the surface to achieve a shine.
When you apply each additional coat within an hour or so it allows the solvents to rise from the previous layer.

I recently painted two metal pendant lamp shades and it took about a ten days for the multiple coats to cure before I would consider ever sanding and re-coating.

Never use steel wool to sand paint.......The metal particles will embed in the finish.
Wet/dry sandpaper is best using a spray bottle with water to flush paint particles away.
I would leave it alone for at least a couple of weeks to cure and start with a light touch and 220 grit wet finishing with 400 wet.
Once you finish smoothing out what you have already applied you could look for a sand-able grey primer and use 400 grit, wet and with a light touch to smooth out the base.
 
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Old 02-09-15, 04:23 AM
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The 2 main things for getting a nice fluid finish is to apply enough paint [multiple coats, letting it tack up between coats] and making sure there is no dust/debris blown into the wet paint. I agree that you need to wet sand [isn't all wet/dry paper black], reprime if needed [followed by more wet sanding] and recoat. It is difficult to get a fine finish using rattle cans the larger the area being painted, the more difficult it becomes.
 
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Old 02-09-15, 06:28 AM
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Thanks

The information you all included below is good to know. I can post a photo if anyone is interested to see what a rattle can job looks like after it's all done.

I can't afford to use professional painting equipment. But I still want to do a good job with the limited resources. I used 600 grit sand paper on the black primer. I only waited 10 minutes between the first three coats. Then I have to wait seven days if I want to paint beyond three coats. These were the instructions on the spray cans.

I'm doing this in my enclosed garage when the winds are calm. Do I really to do a primer coat between layers of white paint?
 
  #6  
Old 02-09-15, 06:42 AM
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If you sand the white paint smooth and don't reveal any bare metal [or bondo] you don't need to use a primer.

While it is difficult to get a nice job with aerosol cans, it can be done. I met a boy once that had a hot rod [very small body] that he painted with rattle cans and it looked nice, I was amazed! I think he said it took 27 cans of spray paint
 
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Old 02-09-15, 09:42 AM
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Geez................27 cans of spray paint !

Can I sand the third coat now, instead of waiting a week when the fourth coat will be ready to apply?
 
  #8  
Old 02-09-15, 09:55 AM
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As long as the paint has cured you can sand it at any time. Soft paint doesn't sand well.
 
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Old 02-09-15, 10:13 AM
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The only reason I would wait to sand until it's about time for the next coat is that it helps clean the surface at the same time so sanding now would mean a quick wipe down with something before painting the next coat.
 
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Old 02-09-15, 10:17 AM
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Good point Mitch! Sanding the paint takes away a lot of the sheen and makes it easier for dirt to attach itself to the paint.
 
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Old 02-09-15, 01:53 PM
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I was thinking that rough, gritty, particle finish might retain more dirt and make it more difficult to sand when the time comes. Is this not the case?

Also, will clear coat make the surface any smoother for applying wax? It was my understanding that you're supposed to use flat under clear coat. Can I even use clear coat over gloss?
 
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Old 02-09-15, 02:03 PM
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Some clear coats can be applied over some gloss paints but it's mainly for the base coat [flat] clear coat systems. An over simplification is the clear coat is the same paint as the gloss paint minus the pigments. It's possible for a clear coat to be slicker than the underlying paint but it's just as possible for the clear coat to be not as slick. A lot depends on the conditions it's sprayed in along with how it was applied. Personally I wouldn't add the clear coat, if anything, I'd apply an extra coat of paint ... it can be buffed out to make a slicker finish IF the paint is thick enough [so you don't buff thru it]
 
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Old 02-09-15, 02:51 PM
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Honestly, you maybe over thinking this a bit.

Enamel paint is pretty durable and can look good if you apply it how it was meant to be used.
Multiple paint coats, even high end vehicle finishes are applied in one session.
That is you apply a light coat to cover, let it tack up then apply successive medium coats to build the thickness, then finish with a medium wet coat to allow the solvent to rise to the surface which is where you get your shine with enamel paints.

The technique you describe where you apply the finish, let dry, then sand between coats was used many years ago with automotive lacquer finishes.
 
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Old 02-09-15, 02:56 PM
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Well put Greg

Even the old lacquer finishes where applied multi coats wet, the more lacquer there was on the vehicle, the more you could buff it which is where the ultimate shine came from. All dry paints/primers benefit from sanding prior to recoating. Sanding both promotes good adhesion and removes anything that might be on the current finish that could be a determent to the new.
 
  #15  
Old 02-10-15, 03:46 PM
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Ok. Thanks for the additional information. I'll resume this weekend.
 
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Old 02-17-15, 05:51 AM
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I'm still working on it and I'm up to six coats. It took considerable time to sand it properly. I'll let it cure for a week or so if that sounds ok, and then add another coat and see what it looks like
 
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Old 02-17-15, 07:02 AM
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Is there a special reason for multi coats with it drying in between? Normally when you paint a car [or fender] you apply 3-4 coats but only let it tack up between coats. Basically each subsequent coat 'melts' into the previous tacky coat resulting in one thick coat. That cuts out having to sand between coats. IMO the only reason to sand the dried fresh coat of paint and apply another coat is to fix a defect in the finish.
 
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Old 02-17-15, 11:40 AM
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I'm waiting a week to resume mainly because I have more time on the weekend. Also the instructions on the spray can gave me the understating that I should wait seven days after each group of fast three coats.

This means that I sand after each group of three coats, and the final coat. Is this ok?
 
  #19  
Old 02-17-15, 11:51 AM
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Anytime the paint has dried you need to sand before applying another coat. Normally you do any sanding after the final coat has been applied.

I've never sprayed larger areas with a rattle can so if their directions are different - follow them.
 
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Old 02-17-15, 04:36 PM
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Understood. I'll post a photo whenever it is done.
 
  #21  
Old 02-18-15, 04:45 AM
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Normally you do any sanding after the final coat has been applied.
I typed that wrong it should have read; normally you don't do any sanding after the final coat has been applied
 
  #22  
Old 02-18-15, 06:27 AM
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Ok thanks. Normally this cheap spray paint leaves a gritty, rough finish whenever you use it. I might have to sand the final coat. But I'll see how it goes.
 
  #23  
Old 02-18-15, 06:51 AM
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When you must sand the final coat you need to make sure it's an ultra fine sandpaper [1500 grit or finer] It's difficult to get the mil thickness needed with rattle cans so there is a danger of sanding thru the paint.
 
  #24  
Old 02-19-15, 04:57 PM
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Ok. I have been using 600 grit after cured coats and noticed that it is still not completely smooth. But I'll definitely finish up with much finer sandpaper as you suggested.
 
  #25  
Old 02-19-15, 06:06 PM
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I read recently that warming up the rattle can in a hot water bath will help the paint go on better. I tried it and it does really work. Lots more solvent smell but the paint went down beautifully.
 
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Old 02-20-15, 03:38 AM
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600 grit is ok for sanding prior to repainting, 400 grit is the norm. You want to 'scratch' up the paint enough so the next coat of paint will adhere. The ultra fine grits are used when you need to sand/polish the final coat, the extra fine grit makes it harder to spot any scratches from sanding.
 
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Old 02-23-15, 06:32 AM
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Thanks for the additional information. I'll warm up the spray can as suggested. I'm still working on it
 
  #28  
Old 03-02-15, 06:05 AM
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Up to nine coats. Still working on it. Maybe two more and it will be done
 
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Old 03-02-15, 03:36 PM
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I am curious as to why you are putting on so many coats???

We have tried to explain how enamel paint is applied and doing so may coats is not a good thing.
Enamel paint is a solid color, meaning you can not see through it so there is no advantage to building up the finish.

There are a few situations where building up a finish will give you a high quality paint job.
Acrylic lacquer is an old time finish where the dry time is very fast and you fine sand between coats.
Acrylic lacquer is slightly opague and when you build up the layers you add depth to the finish.

Base coat/clear coat finishes also can give you greater depth with more coats of paint.
You apply several coats of base to give your surface an even color then apply many coats of clear to give your finish depth.

You can not see through the surface of enamel paint and more than a few coats will not be of any benefit.
The down side of have a thick finish is it will be susceptible to cracking........stone chips will be very big.

What makes for a quality enamel finish is good surface prep.
One thing that is good to apply in many coats is a sandable primer/surfacer.
It will fill small scratch marks and within reason can be built up to make the surface really smooth.
 
  #30  
Old 03-03-15, 03:56 AM
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Greg, one thing to remember is 9 coats from a rattle can won't equal the mil thickness of 9 coats from a spray gun ..... but even so, I don't understand the need for that many coats! I would have have applied the paint until I got good coverage [however many coats wet on wet/tacky] and only sanding and repainting it if I found defects in the finish after it dried.

that is assuming the metal was paint ready before the finish is applied
 
  #31  
Old 03-03-15, 01:06 PM
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It needed this many coats so far because it had a bit of a splotchy appearance. Remember also, I am relatively unskilled at this and I am using cheap spray paint.

I realize now that I may not have been spraying close enough to the fender. The spray pattern was spreading out too much. I moved the spray can nozzle a couple inches closer and I got better results with a thicker, smoother coat. So my technique probably needed improvement.

I also switched to engine enamel and that worked better for me too. It is finally taking shape and it shouldn't need more than two more coats.
 
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Old 04-30-15, 07:40 AM
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I just need to sand and I'll be done. I had to lay off for awhile to heal from hernia surgery. I'll post a photo soon.
 
  #33  
Old 05-02-15, 03:21 PM
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Here is the spray painted fender. I know it doesn't look great. I just used universal white paint. I'll attach the pin striping and fender emblem later. Click on the link below.




Spray Painted Fender Photo by paisano184 | Photobucket
 
  #34  
Old 05-02-15, 03:37 PM
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Any reason you didn't use the right color paint at least for the final coat
 
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Old 05-02-15, 04:34 PM
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Not worth the trouble or expense to try and match 23 year old paint job. Also they don't have the right match in spray can. There is always something that needs to be maintained or repaired on this truck. I'm more concerned with the truck being mechanically sound. Thanks for your help.
 

Last edited by bluesbreaker; 05-02-15 at 05:09 PM.
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