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Masking to paint firewall, doorjambs, etc.?

4K views 5 replies 4 participants last post by  baddbob 
#1 ·
Dumb question here that I haven't seen asked before.I'm about ready to paint my firewall ,then put my engine and trans. all back in, then latter paint door jambs, and window frames, before glass is installed etc.I plan on driving it some in epoxy primer on the body before final paint.To not have to much overspray on the body,should I mask it of on the edges when painting these areas?Would you tape right at the edge?Will this create any problems painting to that edge latter when I do paint the rest? Thanks Jim
 
#2 ·
I never mask the edges off. Just let my paint overlap the primer on the rockers, fenders, ect. Shouldn't have to use quite as much pressure as if you were spraying the entire car. And if you are going to be letting the epoxy sit over a week, you will have to scuff it anyways, so you can wet sand it smooth when you continue. Plus sounds like the paint is going to have plenty of time to cure before you are going to be painting over it. It can be a problem painting over the oversprayed areas if the paint is too fresh, but with it sitting over a day or so you should be fine if using a activated paint. If you really feel like masking the edges I guess you could tape past the edge and roll the tape edge back till its at the edge. I don't like sanding off sharp tape lines. I wouldn't bother taping the body off though.
 
#3 ·
I guess that's what I was wondering.Is it harder to deal with a paintline at say the outer edge of a doorjamb where it meets the exterior panel, or dealing with overspray when you paint the exterior 6 months latter?I was thinking if I get it running, it may get driven a bit in primer, and the overspray won't add much in the looks dept.I'm using Deltron bc/cc.
 
#4 ·
"Basics of Basics" Painting jambs

"Basics of Basics" Painting jambs
By Brian Martin

There is as many ways to paint jambs as there guys doing it. Unless it is an out and out show car I say paint the jams and then paint the outside. Many guys will say do it all at once with the panels off. The extra work and chance of damaging your new paint are so great, I say save that for the out and out show cars. If tape off the jambs well, you can barely tell the difference.
These are a few things I have learned that save a lot of work. First off, when you paint the jambs, apply both color and clear. DO NOT let the overspray go out onto the outside! This can cause HUGE problems along with the extra sanding that can be avoided. Unless completely removed, that overspray can ruin you work. The solvents from the paint on the exterior will get under the thin overspray and lift! What you want to do is be sure that the outside is TOTALLY done and READY to be final sanded and painted BEFORE you do the jambs. Now, tape off the outside along the jamb edge with at least 18" paper so you don't get that direct overspray out on the exterior. I tape the paper up to about 1/8" from the edge of the jamb. Then take your tape and "backtape" to the edge. This is when you lay the tape up to the edge on the outside so it is hanging over the edge, then gently fold it back, exposing the jamb but keeping the outside covered right up to the edge. This back taping will make a "softer" edge and be much easier to sand.
Go ahead and paint and clear the jamb, and remove that last tape that is back taped while the clear is still a little wet if you want (not necessary but you could choose to do that) the clear will then flow a little at the edge and leave you will even less of an edge to sand off.
Now when you paint the outside tape off the jambs up to about 1/8" or 3/16" from the edge so the seam won't be seen when the door is closed. Sand the exterior including that little edge left from the jamb paint and do the last little bit of jamb paint up to the new tape line with a gray scuff pad. I even will put that tape a little bit further away (about another 1/16") from the edge and after the scuffing with the gray scuff pad, apply a fine line (the blue plastic tape) tape over that last tape but hanging over the edge onto the new jamb paint that 1/16" bringing the line up to the original desired 1/8" to 3/16" from the edge. This will ensure that your jamb edge doesn't peel.

You could also use "aperture" foam tape that 3M makes. It is a rope made of foam with adhesive on it and is like "back taping" it leaves a "soft" edge.
I can go even more anal for you.
This may not work well in your jambs but if you can open the doors before clearing you could do it. I have found an even better way to all but eliminate that edge.
Tape off the edge as described with the extra line of fine line tape over the last 1/16" of new jamb paint (this works with when painting up to any paint actually, it doesn't need to be new paint you are painting up to). Then add ANOTHER strip of fine line the same way, over the next 1/16" or 3/32" getting up even closer to the jamb edge. Now, after you paint the color on the outside, you remove that last fine line added BEFORE you clear the exterior. Now, you will be burying the edge of the base coat under the clear! You don't have to do this by any means but it adds to that detail that is almost like you removed the doors to paint.
 
#5 ·
You will be sanding either way. If you have a sharp line, you may brake through your epoxy primer getting rid of the line. But if you are going to be driving around for awhile in epoxy primer, you probably are going to need to sand or scuff it and put on another coat anyways. Most epoxys have a window of about a week, after that you need to scuff it. Check your tech sheets on the epoxy you are using. As far as the overspray on the outside, it can lift if it is really fresh when you paint over it. but normally not a problem if it has sat a little while. When it comes time to continue, most of it you can wetsand off. You shouldn't be getting a real lot of overspray all over the car, You shouldn't need as much pressure as you would doing large panels like when painting the outside. Like a lot of things everyone has different ways of doing it. I guess you can say there are many ways to skin a cat.
 
#6 ·
You want to shoot the interior surfaces firewall and then assemble but not mess up the clean exterior appearance of your epoxy primer. I'd shoot these areas then sand off the overspray then mask off the painted areas and apply two more coats of epoxy over the exterior reduced as a sealer. The tape lines on the edges of your epoxy will be nothing to sand out before final paint. You're going to have some sanding either any way it's done.
 
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