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HELP! - Need assist with putty, sanding, primering


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Ok, I REALLY need some help with this one....

I an attempting to build a 1970 Hemi Barracuda out of a '71 Cuda Street Machine and have hit a wall with this issue. First the pix showing my progress, trouble, and tools.

Using two different kinds of putty, Milliput and Squadron White Putty...

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Trying to use Krylon Primer and Tamiya Dull Red as a base, Guards Red will be the finishing coat. Sanding sticks are from 100 grain, then 400, 600, 800, and finally 2000 (have higher for polishing pads...)

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Alligator texture from the Krylon showing through the Dull Red, front fender will NOT SMOOTH OUT, no matter how hard I try... (look carefully at the upper part of the fender, you can still see the putty coverup of the shark gills. I swear they were smooth before I started!)

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Front shot of the valences, not looking any better...

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Other side, same problem as everywhere else, only covered-up gills are even more pronounced!!!

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Why I may just want to strip everything. Nothing will smooth down AT ALL...

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The real issue here is with what I did with the Milliput. I used a good portion of it behind the grille to fill in gaps on either side and to get the valences to try and mate up, beforehand they were REALLY buck-toothed. Milliput dissolves in water to help the sculpting process, so I have no idea what will happen if I dip this in Purple Power to remove all the primer and paint. I tried to stick with a single-direction stroke when sanding after the primer, but it completely refused to smooth out, and now the car body seems like it has an alligator-skin appearance in direct light. In addition, the putty just will not thin out to where I can get an even smoothness back to the body, and laying more putty down just causes it to bulge out more. I actually thought about puttying up the entire front quarter panel, top to bottom, and then trying to smooth it all out front to back, but I shouldn't have to do that, should I? How is it everyone else can put small amounts of putty down and come through with a natural body paintjob?

I'm in Richmond, VA. I will GO to an expert's house to watch and learn this. I have had pretty good success with sanding and puttying before, but on a much smaller scale.

HELP?!?!

Edited by Drake69
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It sounds like you're basically doing it right. Milliput is probably ok to crudely fill a large opening, but I usually uses some plastic filler and putty. Squadron white is not too bad but I've left it on the shelf long ago. It will shrink over time .. similar to one part body putty (1:1). It's ok for thin coatings though.

The best body putty is the 1:1 two part stuff. This will not shrink and cures fast. Bondo and Everlast are two commonly used ones, but I don't have the exact type at hand. I'm sure others will give some exact names.

The sandpapers you are using are fine.. I usually only go to 400 or 600 grits before painting. Do use a sandable auto primer as a final smoothing. It will show any areas needing more putty and it fills small scratches. Use a padded sanding stick or just wrap the paper around a stiff board, Popsicle stick or coffee stirrer. anything stiff to get a smooth transition to the plastic and an even surface.

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That Krylon primer is a real problem. Too hot for plastic and by the pictures it looks to have crazed the plastic, possibly rendering that body unusable. Unless you want to use Tamiya primer when it becomes available again, use Duplicolor filler primer. Also, why use Testors Guards Red ENAMEL when Tamiya makes the same color in their excellent LACQUER formula?

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Sometimes a difference in toughness between the plastic and the filler can cause problems as it sands away at different rates and then there is the possible shrinking problem. You can try disolving sprue in liquid glue to make a goop for small filling jobs in plastic, it will sand out the same. You can also try gluing in scrap plastic so as to reduce the amount of filler needed. A thin fill is usually better than a thick one. As said above, using the paper with a stiff backing will take off the high spots better. I don't like the foam boards because I think that they 'give' too much.

I ALWAYS use Tamiya primers with Tamiya laquers.

You may be able to sand out the crazing on the body, maybe by repeated sandings and primings until (hopefully) smooth.

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The lhs didn't have Guards Red in Tamiya so I bought what I could get. I haven't sprayed it yet but it would have been after I had a smooth body. The krylon was picked up as an alternative to Tamiya primer on suggestion by others, but it looks to be a Big Mistake.

I need a Reliable primer suggestion until Tamiya can get its act together!

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Sorry for your primer woes. I was just down to my last drop when I managed to grab a couple of tins. Does someone know what primer recommended for Testors' laquers, maybe it would work for Tamiya laquers as well?

Edited by DanielG
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The lhs didn't have Guards Red in Tamiya so I bought what I could get. I haven't sprayed it yet but it would have been after I had a smooth body. The krylon was picked up as an alternative to Tamiya primer on suggestion by others, but it looks to be a Big Mistake.

I need a Reliable primer suggestion until Tamiya can get its act together!

The answer is Plasti-Kote sandable primer, T235. But, first scribe all panel lines. Spray your project with two lite coats of primer. be careful as this primer can build quikly. After the primer is fully dry give it a lite sanding with 1000 grit sandper. It will be very smooth.

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Duplicolor. I use it almost exlusvely, regardless of what the topcoat will be. I mainly use the sandable type, which allows for sanding the primer to a smooth finish, which makes for a better paint finish. I've also used the Color Shop primer from Duplicolor. It comes in a quart can, prethinned for spraying. Very economical if you have an airbrush, though you may consider thinning it a bit more than how it comes. Valspar also has a decent primer in their tractor paint line (yes, tractor paint). I get at the local TSC.

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I don't have a ton of experience with it, but I've been using Duplicolor white sandable primer. It goes on thin, I've had no crazing issues, and I've sprayed Duplicolor, Testors, and Tamiya lacquers, and MM and Testors enamels over it with no problems.

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it looks to me like you have what is called ghosting

the styrene is molded under very high pressure

when you remove the molded in gills you create an escape point for the presure stuck in the model

once you apply the primer the chemical reaction will make the styrene somewhat liquid again and it will press out where you removed the gills

so what you want to do is seal that area up

one way to do (as mentioned before) is sprue melted in glue

another way is to seal it with future or to put some superglue mixed with baking soda over it

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Thanks for all the comments, I am really learning a ton here!

Alright. I managed to save myself and this car body, but it wasn't easy. The first thing I did was sand as much as I could using 400 grit paper until I had the best surface I could get, then with a hobby knife rescored the door panels and side markers as best I could. a while back my father told me of a trick where he used a flat black base with a heavy sitting lacquer paint to mask bad primering, so I started with a few coats of Tamiya F. Black, sanded with 2000 grit paper, then hit it with ModelMaster One-Coat Revving Red Lacquer. I'll let the pictures speak for itself...

Cuda20.jpg

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It actually de-emphasized the bottom panels and smoothed out all the scaling issues from the primer! Passenger-side gills disappeared completely, driver-side takes close scrutiny to see.

Thanks for all the recommendations and tips!

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  • 8 months later...

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