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Author Topic: Help with primer application  (Read 6326 times)
nalmeida
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« on: January 31, 2014, 11:18:52 AM »

Hi there guys, looking for some help regarding primer application. I've been making some projects in styrene but only recently I decided to start painting them. I read that applying some sort of primer should be the first step so I bought the Vallejo Primer for plastics and metal.

I applied some coats only to discover that the the paint/primer doesn't stick well in the areas that were exposed to the styrene contact cement. I use the revell contacta and usually I don't mind that it flows out of area because it dries transparent and I get a better bond. The problem is that now I don't know what to do, is there another brand that sticks to the cement exposed areas?

Here is a picture of the problem:



* IMG_20140131_170321_E.jpg (187.69 KB, 802x602 - viewed 761 times.)
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marc_reusser
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« Reply #1 on: February 02, 2014, 01:46:38 AM »

Nelson,

I am not familiar with the Revell contacta, so I can’t really speak to the possibility that the cement itself is possibly causing the issue, but if it is something like the Tamiya adhesive, that leaves a film on the surface, this could be your problem. If not from the glue itself, then from the shiny/smooth/slick surface it creates. One of the things I always do before painting is to take a fiberglass pencil and lightly go over any glue areas and joints, to dull them down, or get rid of the exposed/excess glue. (this also gives a very small amount of tooth to the surface).

Usually when primer or paint is not adhering to the surface it is an issue of an unclean substrate/surface.....if you did not do so, you should always wash all parts and pieces with warm water and dish soap using a larger soft brush to get into all the corners and crevices. (Do not use hand soap or any soap wit moisturizers or such, as these can/will cause issues with paint adhesion). If you did not wash the parts, a reason that the primer may be adhering better on the plastic but not on the glue, is because the glue leaves some form of surface residue, that needs to be washed away before painting.

Lastly, it could just be that the primer doesn’t play well with the glue. Bad chemistry. This to me is the least possible (and I am not in any way defending the primer mfr)…..as most primers are made to bond to properly prepared substrates (though there is always a chance of a bad batch).

FWIW…. I would recommend trying the Gunze Mr. Surfacer 500/1000/1200 primer (directly from a spray can)…it is IMO the best out in the hobby market today.

« Last Edit: February 02, 2014, 02:01:43 AM by marc_reusser » Logged

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nalmeida
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« Reply #2 on: February 04, 2014, 05:45:43 AM »

Thanks a lot for your feedback Marc. You are right, the areas exposed to the glue are very shiny and smooth and that might be the problem. Where can I find a fiberglass pencil? Is it restricted to the model painting area or can it be found on other places? O would like to find one in my area so I can test it. I thought about sanding the areas but the surface has to much detail to do it.
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« Reply #3 on: February 04, 2014, 05:50:01 AM »

Hi, Nelson,

you may find it in an artists supply or maybe in a stationery shop. In the age of making technical drawings by hand this was used to erase china ink, for example.

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« Last Edit: February 04, 2014, 07:19:28 AM by Hydrostat » Logged

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« Reply #4 on: February 04, 2014, 06:08:51 AM »

Hi, Nelson,


a fiberglass pencil

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