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Filling and Testing Seams

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  • Member since
    June, 2016
Filling and Testing Seams
Posted by Pwaszak on Monday, August 14, 2017 12:47 AM

Hey all, so seams are the bane of my existence. I fill them, they look good, sand them, and then prime. I think I'm doing it correctly, but seams pop up and stick out like a sore thumb. Is there a technique to 'test' the seam to make sure it's gone before priming? 

 

And if the filling looks good and flush, should I be sanding? Or does that remove the putty in the seam? And should I do multiple layers of putty? 

 

Thanks in advance. 

 

P

  • Member since
    October, 2010
Posted by hypertex on Monday, August 14, 2017 7:24 AM

Yeah, that keeps happening to me, too. For me, priming is part of the filling process. I use a sandable filling primer and if a seam shows itself after I apply it, it is usually shallow enough that more primer and more sanding will fill it up. If it is too deep, I will fill it with Mr. Surfacer 500 from the bottle.

To check the seam before priming I do a few things. First I use a small flashlight to look for flaws. Hold it at low angles to the plastic to create shadows. This is how I look for seems when I judge shows, that's where I learned it. Another thing you can do is instead of using your eyes, use a blunt but pointed instrument to feel for a seam. I have this steel dental thingy that doesn't scratch the plastic, it also doubles as a putty spreader. I just move it across the seam to feel for indentations and rough spots.

A third thing I do is use a bit of silver paint and apply it to the seam. Silver paint shows even the smallest flaws. If it shows a small seam, just sand off the paint and fill the gap with your favorite filler.

And yes, it often takes multiple layers of putty to properly fill a gap.

Hope that helps

  • Member since
    August, 2013
Posted by Jay Jay on Monday, August 14, 2017 10:09 AM

I've found that if you use a laquer based filler, a laquer based primer will eat some of the filler allowing the seams to show.  My solution was to use water based perfect Plastic Putty on the seams then my usual Tamiya primer or Alclad Primer resulting in less work and better seams.

 

 

 

 

 

 I'm finally retired. Now time I got, money I don't.

  • Member since
    June, 2016
Posted by Pwaszak on Monday, August 14, 2017 2:54 PM

Thanks guys, I'll give your suggestions a shot and see how it works out. Much appreciated!

 

Let me ask one more Q . . . After discovering a seam after priming, do you sand off the primer and apply more putty, or just apply the putty over the primer? 

 

Annnnd one more edit question! I'm using perfect plastic putty . . . I know you can use a wet qtip to smooth it. Do you do that after it dries, or immediately after applying it?

 

 

  • Member since
    December, 2002
  • From: Bury St Edmunds, Suffolk, England
Posted by Bish on Monday, August 14, 2017 3:01 PM

Get an enamel silver paint pen. One of the guys sent me a Testors one over and its ben a massive help in improving my seams. Tamiya also does them.

''I am a Norfolk man, and i glory in being so''

  

On the bench: Trumpeter 1/35th AS90   

  • Member since
    March, 2013
Posted by patrick206 on Monday, August 14, 2017 3:01 PM

If the seam is a large one, I expect trouble with it. In that case I heat and stretch sprue, to a fine thread size. I press that into the seam with a bit of pressure, then lightly flood the area a couple of times with thin liquid cement.

After a few minutes and giving the cement time to evaporate a bit, I use a dental metal spatula with a flat surface, to press the softened sprue further into the seam. That leaves the stretched sprue, still slightly above the level of the joined plastic surfaces.

Let stand over night to dry and harden, file and sand smooth, flush with the seam sides. Almost always gone. I avoid fillers, as over time they can shrink, crack and get really ugly under the paint.

Patrick

  • Member since
    December, 2013
  • From: Orlando Florida
Posted by route62 on Monday, August 14, 2017 4:00 PM

i also use PPP and wipe with wet cotton bud usually within a few minutes as it dries quicky.  I also do the silver paint right away and apply more PPP as needed.  This way I can fill a seam within minutes instead of fill-prime-fill.

Also when I am gluing, using tamiya thin cement or similar, I line up the seam, apply the glue, allowing the glue to flow into seam, then as the plastic softens I apply a little pressure to the seam.  I will see very small plastic balls/bubbles press out of the seam.  Once the plastic is dry and hard, I can sand away the plastic that pressed out and almost always this reduces or eliminates seam filling.

  • Member since
    January, 2006
Posted by Paul Budzik on Monday, August 14, 2017 10:42 PM

I like to stay away from solvents ... I especially don't like the disolved styrene techniques ... they might look OK in the short term ... but over time the solvent shrinks and you have some surprises ...

 

Paul

  • Member since
    December, 2013
  • From: Orlando Florida
Posted by route62 on Monday, August 14, 2017 10:59 PM

As Paul is a modeling legend his sage advice is well received. I have built kits over 15 years old with no seam issues using solvent based glue.

I can sand the seam within 1 hour though I usually will do other tasks and allow a little more time.  I find CA glues to be brittle, unpredictable, difficult to sand, set up too quickly to allow alignment of halves and create more seam issues then they solve.

Paul has been building much longer then I have and is published. I am a rank amatuer when compared to him.  Based on my experience with CA I tend to avoid it but Paul would know best.

  • Member since
    June, 2016
Posted by Pwaszak on Monday, August 14, 2017 11:50 PM
I think this might also lend light to why I'm having problems. Usually I leave a space between the parts I'm gluing, apply the glue, then push the halves together. Maybe I should try lining them up before I apply the glue. Thanks everyone, you've all been very helpful. I do get frustrated when I get far along on a build only to run into a snag or muck something up, that's where I put the whole project off or even just throw it out. I need to stop being a perfectionist and just finish my builds, warts and all, if anything just to learn and develop my skills.
  • Member since
    January, 2006
Posted by Paul Budzik on Tuesday, August 15, 2017 11:04 PM

Please don't misunderstand ... I'm not totally against solvent cements ... just the overapplication.  Once you dissolve styrene, it takes ages to ever evaporate and get hard so I don't like seeing it used as a filler, but as a glue, it can't be beat.

 

Paul

  • Member since
    July, 2013
Posted by modelmaker66 on Tuesday, August 15, 2017 11:53 PM

Pwaszak
I think this might also lend light to why I'm having problems. Usually I leave a space between the parts I'm gluing, apply the glue, then push the halves together. Maybe I should try lining them up before I apply the glue. Thanks everyone, you've all been very helpful. I do get frustrated when I get far along on a build only to run into a snag or muck something up, that's where I put the whole project off or even just throw it out. I need to stop being a perfectionist and just finish my builds, warts and all, if anything just to learn and develop my skills.
 

I definately try to keep the parts as close as possible so the glue runs off into the length of the seam with capillary acion and the glue is right there when joining the parts.

  • Member since
    January, 2014
Posted by Silver on Wednesday, October 11, 2017 1:17 PM

Try gap filling cynical glue or super glue.Then wet sand.

  • Member since
    November, 2009
  • From: Twin Cities of Minnesota
Posted by Don Stauffer on Thursday, October 12, 2017 9:21 AM

Two of the things I like about auto body putty is that it dries fast, and works fine with lacquer primers.  It does shrink a bit, but I can live with having to do two coats.

 

Don Stauffer in Minnesota

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