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Filled seams showing through paint

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  • Member since
    August, 2014
  • From: Southeastern Virginia, USA
Filled seams showing through paint
Posted by rustyroach on Friday, September 13, 2019 7:30 PM

Just finished a top chop on a deuce 3 window. It required stretching the roof to get alignment of the pillars. I used styrene strip to fill the gap with reinforcement inside. I filled the small irregularities with Tamiya white, sanded, primed, sanded, primed again. Looked great. Sprayed the color (Dupli-Color). When it dried it still looked great. Ran the grits down from 2000 to 12000 and polished. Thats when I saw the seam in the roof. I thought I had the seam perfect before the color coat. Dont know where I went wrong. Ill bet someone does. Love to hear it. A lot of work ending in disappointment.

Rust Never Sleeps

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Monday, September 16, 2019 6:58 AM

What are you using for glue? Regular, solvent based model glue can continue to 'work' the plastic long after the initial work was done. The chemical reaction between the glue and the plastic continues long after the glue has seemingly hardened. The problem seems worse when using tube glue or the Testors stuff in the black bottle. Thin liquid cements have less of an effect when used sparingly, but with heavy use they can be a problem as well. If you used soft Evergreen plastic as filler material, it seems particularly susceptable. Traditional model cement creates the best bond, of course, but there were a number of times, especially in my younger days when a glued joint in body work would show up weeks after a model was painted and on the shelf. The solution would be using glue sparingly, or waiting out the heavy glue work for a long time, then doing the final finishing of the body work once everything has cured. I also believe that painting a hot paint over the joint before everything is 100% cured aggravates the situation, but that is more of a hunch than knowledge.

Something else I do to make body work disappear under the paint. After the body work and filling is done and sanded smooth, I brush on a coat of Gunze Mr Surfacer (1000 or 1500). Mr Surfacer is a thick, lacquer based primer that feathers out really well. It fills small pores in the filler and makes the transistion line between plastic and filler disappear. This stuff is also the cat's pajamas for filling small defects such as panel scriber slips, etc.

I don't know the actual cause, but that's just a couple of thoughts off the top of my head.

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

  • Member since
    August, 2014
  • From: Southeastern Virginia, USA
Posted by rustyroach on Monday, September 16, 2019 7:23 PM

Trevor, I think you nailed it. I did use Tamiya liquid to glue the Evergreen strip. And.... moved the project along at an unusually rapid pace. I was excited, I guess. There were other areas that ghosted out, too. Like the cowel vent. I thank you for your very valuable input. Because I am about to do something I cant afford to screw up. I really appreciate it.

Rust Never Sleeps

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Tuesday, September 17, 2019 6:26 AM

Rusty, glad I could help. Model cement provides the best bond, but if you need to work rapidly, or simply wish to avoid this problem altogether, CA glue makes a good strong joint without the softening of plastic that occurs with model cement.

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

  • Member since
    August, 2015
  • From: Hamptonville, NC
Posted by TarheelRick on Tuesday, September 17, 2019 6:49 AM

I have the same issue with a custom 61 Ford I am building.  A member of another forum suggested the same thing, give the glue time to do its thing, a dehydrator may speed up the process a bit.  Another hint he passed on was to put a thin layer of super glue over the puttied area, sand it, then prime the body.  The super glue will seal any porousness of the putty.  Hope this helps.  The 61 Ford is back in the box, I really rushed the paint and am now looking for another color.

I build models because I can't afford the real thing!

  • Member since
    March, 2019
  • From: Quitman, Texas
Posted by LostInStyreneAnd... on Tuesday, September 17, 2019 7:36 AM

This is Great information!    I'm about to start laying out the body for my latest scratch built racer, and the current 'picture in my head' will require a good bit of small pieces and filler for contouring.   Thank Y'all!

Eric Automobile

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Tuesday, September 17, 2019 10:47 AM

Any time large amounts of filler are to be used, especially if it is thick layers, use a two part, catalizing filler. It cures faster without shrinkage, and won't attack the plastic.

Conventional, one part (solvent based) fillers will act just like model glue, in that they will appear to be cured, but will continue shrinking for quite some time. And the lacquer based one part fillers, such as Bondo for autobody use, will attack and distort the plastic over time when used heavily. I do use this stuff, but only in small amounts or very thin layers.

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

  • Member since
    January, 2011
  • From: long island, new york
Posted by chucky on Tuesday, September 17, 2019 7:23 PM

Well stated, Trevor. I totally agree. Solvent-based putties like Nitro Stan were the standard of the industry for decades for filling minor defects in body work prior to paint. Even on the 1:1 cars, shrinkage of the glazing putty or heavy application of lacquer-based primer became such a quality-control issue that the two-part glazing putties and epoxy high-build primers were developed. No reason to expect different results in model scale, especially if lacquer-based primers and color coats are used. 

chucky

  • Member since
    August, 2014
  • From: Southeastern Virginia, USA
Posted by rustyroach on Wednesday, September 18, 2019 6:10 AM

I appreciate everyone's interest and input in this subject. Im really glad I asked. Thanks again!

Rust Never Sleeps

  • Member since
    August, 2014
  • From: Southeastern Virginia, USA
Posted by rustyroach on Sunday, September 22, 2019 5:06 AM

I think I would like to try the two part filler you mention on a four door/two door conversion. What do you use, specifically? I want to be sure to not to screw this one up.

Rust Never Sleeps

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Wednesday, September 25, 2019 7:17 AM

rustyroach

I think I would like to try the two part filler you mention on a four door/two door conversion. What do you use, specifically? I want to be sure to not to screw this one up.

 

To be honest, I rarely do heavy body work so have no need for two part fillers myself, so can't provide a personal recommendation. However, I know some guys are using Evercoat products such as Eurosoft and Rage, but these products come in something like 1 quart cans, so quite a lot of stuff for the model builder, and it can go bad over a period of years. It may be a good choice if you do lots of building that required heavy filling.

Bondo two part Professional Glazing Putty is much cheaper and is available in a much smaller tube, and some builders highly recommend it. Just be sure to get the two part stuff, as Bondo also makes a one part glazing putty that comes in an identical tube.

Either of these products are available in auto parts stores.

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

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