SterlingStang13 Posted January 18, 2015 Posted January 18, 2015 I am building a model of my 1:1 car (2013 Mustang) from the Revell 2013 Boss Mustang kit. The hood in the Boss kit has hood vents where as my car does not so I have filled them in with bondo and have done the best that I can seem to do in getting an even primed surface. In most scenarios you can't tell the hood vents existed before, however I can still see where the hood vents were under direct light. I've attached a picture showing this. Will this show through my paint job once I get to that stage, or am I being too picky? I'm a perfectionist and tend to find myself being too harsh on myself a lot of times. Thanks, and by the way this is my first model.
MeatMan Posted January 18, 2015 Posted January 18, 2015 If it shows through the primer (which I can see it does) it definitely will show through the paint. Been there, done that.
MonoPed Posted January 18, 2015 Posted January 18, 2015 Yes, those will show through the paint. keep working them til they disappear.
Jeff Johnston Posted January 18, 2015 Posted January 18, 2015 Yes they will. One thing you can do is fill that in with a light glaze of super glue, then put a drop of ca glue accelerator on it. Then sand it smooth. I find this method works best for me. I only use bondo to fill sink marks in bodies. It'll work on that but you might still get ghosting.
SterlingStang13 Posted January 18, 2015 Author Posted January 18, 2015 I figured as much. Any tips on how to work them out? I've already sanded and reapplied primer 4 times now.
hgbben Posted January 18, 2015 Posted January 18, 2015 You might have better luck cutting the vents out and gluing in a filler piece
vintagedragcrazy Posted January 18, 2015 Posted January 18, 2015 Try using auto spot putty in the tube and sand then prime that works for me sometimes. Vince
Psychographic Posted January 18, 2015 Posted January 18, 2015 In my experience with dealing with this sort of thing you have to sand down past the surface of the plastic. Imagine the body being a road surface and your sanding a shallow pothole where the vents are, then filling it in. I use a styrene/MEK mix to make a filler. Use a thin layer and give it a few days to a week for the MEK to evaporate, then sand it smooth.
Ace-Garageguy Posted January 18, 2015 Posted January 18, 2015 (edited) Welcome to the forum, Josh. Glad you came here to get advice before ending up with a disappointing paint job. Like you, I'm hyper-critical of my own work too, and I don't accept solutions that kinda work pretty good most of the time.. I do a lot of heavy mods using bondo as a filler, get consistently good results, but there are several factors to consider. 1) Some of the more recent kit plastics are a lot softer than they were years ago, and react with the primers...often causing swelling, ghosting, or even crazing. All you can do is to apply relatively light coats of primer, and give it at least 10 minutes of "flash" time between coats. This allows the solvents more time to evaporate out the top of the primer, rather than being trapped where they may be more likely to soften underlying plastic. 2) It's imperative your bondo is mixed correctly, which I'm sure you got right. If somehow it got too little hardener, it will shrink every time primer hits it. I had been doing bodywork for years on 1:1 cars and thought I had it down, but mixing the really small quantities you need for a model can be a challenge 'til you've done a lot of it. 3) When you're filling surface details, it's sometimes best to sand them away, leaving a depression where they were, and to build your filler up to the level of the surface again. This can be a factor because, if you don't thoroughly scuff down inside what you're trying to fill, the bondo may not adhere well down inside the filled detail, and may pull away in places, squirming around and making the surface forever unstable. You can't kill imperfections in an unstable surface. 4) I get ghosting of bodywork showing through, just like you have there, all the time now...again, primarily due to the difference in hardness and shrink between the filler and the kit plastic. All I've ever found that works is to do what you've been doing, but when you sand next time, try to only take enough primer off the surface to eliminate the raised ghost-marks, but don't go deep enough to see the plastic again. Spray several light coats, give them plenty of time to flash, sand with 600 grit wet or finer, and repeat as necessary. When you can spray a medium coat of primer with nothing lifting, you're done. Let it shrink in for a week or so, sand one final time with around 1000 grit, wet, and paint. I chopped the top on the car in this link, and the sail panels and mold seams all over the car gave me the same kind of grief you're having. Patience finally won out, and it looks the same today as it did in these shots taken 2 years ago...no long-term ghosting either. http://www.modelcarsmag.com/forums/index.php?showtopic=58430 PS: You're going to get a lot of differing advice. The only way to be sure you'll have a solution that works every time for you is to experiment until you have a procedure you're happy with. Edited January 18, 2015 by Ace-Garageguy
Snake45 Posted January 18, 2015 Posted January 18, 2015 Yes, that will show. Paint never hides anything. Hit that area, right on top of the primer, with superglue. Let it dry, then block-sand it flush. Reprime. If you still see it (and if you do this right, you shouldn't), repeat. I usually now use superglue to "seal" any putty work, as it will not shrink over time. (Superglue Gel makes a darn fine putty itsownself.)
Mike_G Posted January 18, 2015 Posted January 18, 2015 CA dries harder than styrene, which makes it easy to undercut if you use too fine a grit
Snake45 Posted January 18, 2015 Posted January 18, 2015 CA dries harder than styrene, which makes it easy to undercut if you use too fine a grit That's why it's important to block-sand. The block doesn't care how hard or soft the sanded material is, it's going to keep cutting until everything is level. Also, I've found that if sanded within 24 hours, CA isn't THAT much harder than styrene. Let it sit a few days though and some of it can get quite hard.
Guest Posted January 18, 2015 Posted January 18, 2015 Sand your hood very lightly with 600. Do not sand through the primer where the vents are. Brush a coat of future floor polish (now labeled Pledge With Future Shine) over just the vents. Allow it to dry overnight. Spray a couple of light coats of primer over the vents. Allow the first coat to dry at least 15 minutes before you spray the second coat. If you have a different color primer (paint will work also), spray a mist coat holding your spray can or air brush far away over your primer. You don't want coverage. You just want a fine see through mist. This creates what's called a guide coat. When all is dry, begin wet sanding with 1000 grit. You'll notice right away that your different color primer or paint will remain in the low areas. Those are the areas that need more sanding. Once you get all of the different color sanded away,stop sanding. It's now ready for paint. I don't know what kind of primer you used. But, I highly recommend using Plasti Kote Sandable. If you begin with light coats allowing each to dry for 15 minutes, you can avoid this problem in the future.
Art Anderson Posted January 19, 2015 Posted January 19, 2015 Welcome to the forum, Josh. Glad you came here to get advice before ending up with a disappointing paint job. Like you, I'm hyper-critical of my own work too, and I don't accept solutions that kinda work pretty good most of the time.. I do a lot of heavy mods using bondo as a filler, get consistently good results, but there are several factors to consider. 1) Some of the more recent kit plastics are a lot softer than they were years ago, and react with the primers...often causing swelling, ghosting, or even crazing. All you can do is to apply relatively light coats of primer, and give it at least 10 minutes of "flash" time between coats. This allows the solvents more time to evaporate out the top of the primer, rather than being trapped where they may be more likely to soften underlying plastic. 2) It's imperative your bondo is mixed correctly, which I'm sure you got right. If somehow it got too little hardener, it will shrink every time primer hits it. I had been doing bodywork for years on 1:1 cars and thought I had it down, but mixing the really small quantities you need for a model can be a challenge 'til you've done a lot of it. 3) When you're filling surface details, it's sometimes best to sand them away, leaving a depression where they were, and to build your filler up to the level of the surface again. This can be a factor because, if you don't thoroughly scuff down inside what you're trying to fill, the bondo may not adhere well down inside the filled detail, and may pull away in places, squirming around and making the surface forever unstable. You can't kill imperfections in an unstable surface. 4) I get ghosting of bodywork showing through, just like you have there, all the time now...again, primarily due to the difference in hardness and shrink between the filler and the kit plastic. All I've ever found that works is to do what you've been doing, but when you sand next time, try to only take enough primer off the surface to eliminate the raised ghost-marks, but don't go deep enough to see the plastic again. Spray several light coats, give them plenty of time to flash, sand with 600 grit wet or finer, and repeat as necessary. When you can spray a medium coat of primer with nothing lifting, you're done. Let it shrink in for a week or so, sand one final time with around 1000 grit, wet, and paint. I chopped the top on the car in this link, and the sail panels and mold seams all over the car gave me the same kind of grief you're having. Patience finally won out, and it looks the same today as it did in these shots taken 2 years ago...no long-term ghosting either. http://www.modelcarsmag.com/forums/index.php?showtopic=58430 PS: You're going to get a lot of differing advice. The only way to be sure you'll have a solution that works every time for you is to experiment until you have a procedure you're happy with. Bill has it exactly as I found out years ago. Ghosting, such as you experienced, is the result of the difference in materials (styrene next to catalyzed putty) as styrene will be affected by the penetration of lacquer thinner into it, which causes it to swell up slightly, then shrink back as the solvents evaporate, while catalyzed putty (or for that matter, even CA glue) is not affected in the same manner as styrene plastic. My solution to this has been pretty much what Bill Engwer has pointed out--airbrushing light coats of primer over the corrected, modified surface, let that dry thoroughly to the point that the plastic has shrunk back to it's original surface, then lightly sand the area, just to remove all hint of the ghosting, but not through the primer, then repeat the process, until a coat of primer no longer causes the ghosting. A bit time consuming, but it does work! Art
SterlingStang13 Posted January 19, 2015 Author Posted January 19, 2015 Thank you everyone for your help and suggestions! I've got it fixed now. I ended up lightly block sanding the hood using 800 grit paper. Just enough to make the ghosting disappear, and then I hit it with another coat of primer and I now have a nice smooth surface. I am using Plastikote spot filler primer that I had on hand from another project, and I've been waiting 15-20 minutes between each coat. Here are some pictures. I'll probably start a W.I.P thread in the "On the Workbench" sub-forum soon. After 800 grit block sand: Smooth finish:
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