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spray primer makes the plastic brittle
RichPrag
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England - South West, United Kingdom
Joined: September 24, 2007
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Posted: Monday, September 14, 2009 - 12:05 AM UTC
Hi all

I brush paint models with acrylics and so i use a spray primer first so the paint sticks. CUrrently im using Plasti-Kote white spray paint (cos it was cheap) but it goes on and it makes the plastic more brittle, this is especially apparent and annoying with little pieces like undercarriage struts cos they break.

Does anyone else have this problem or know a way to get round it with a different spray primer?

Cheers

Rich
alpha_tango
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Germany
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Posted: Monday, September 14, 2009 - 12:27 AM UTC
Hi Rich

Hmm, never had such a problem. Maybe you applied too much primer that it solved the plastic which weakend it ultimately? Of course this stuff is designed to attack the plastic to make a good bond with the surface but I never heard of a problem like you had.

Did you glue wich CA and maybe activatior? this stuff destroys plastic if not applied very carefully (ask me how I know ...) .. another reason why I avoid CA as much as I can.

hope you can get replacement parts ..

all the best

Steffen
RichPrag
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England - South West, United Kingdom
Joined: September 24, 2007
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Posted: Monday, September 14, 2009 - 01:18 AM UTC
Hi Steffen

Could be that i applied too much primer, ill have to exeperiment with differing levels i think.

Whats CA? I use revell poly cement (i thinkits called that) to glue and sometimes superglue
alpha_tango
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Posted: Monday, September 14, 2009 - 01:23 AM UTC
Hi Rich

CA is cyanoacrylate ... widely known as super glue ... together with the acellerator it really destroys the plastic (but this depends on the plastic used).

all the best

Steffen
Merlin
Staff MemberSenior Editor
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Posted: Monday, September 14, 2009 - 06:10 AM UTC
Hi Rich

I've never heard of the problem you describe either. I think Plasti-Kote is an acrylic paint, so it shouldn't attack the plastic at all. Alternatives? I have used Halford's grey, white and the yellow "filler" primers on various projects in the past with no ill effects.

All the best

Rowan
Tomcat31
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Posted: Monday, September 14, 2009 - 09:13 AM UTC
Unless they have changed the formula plasti-cote paints use to be cellulose based (well they were when I last used them a few years ago) which could explain the brittleness as the cellulose eats the plastic.

Halford's primers are my choice I've even used the red "oxide" primer before with no problems and they're only a couple of quid more than the plasti-cote primers.
Merlin
Staff MemberSenior Editor
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Posted: Monday, September 14, 2009 - 09:26 AM UTC
Hi Allen

The Plasti-Kote paints that I've used are described as "acrylic enamels" and certainly don't smell like celulose paints. But, whatever, I've used celulose paints for years and they've never made styrene brittle in my experience. Yes, they "eat" it if applied incorrectly (i.e.brushed on and worked over), but brittle? No.

All the best

Rowan
stonar
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England - West Midlands, United Kingdom
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Posted: Wednesday, September 16, 2009 - 06:13 AM UTC

Quoted Text

Hi Rich

I have used Halford's grey, white and the yellow "filler" primers on various projects in the past with no ill effects.




Ditto
Steve
RichPrag
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England - South West, United Kingdom
Joined: September 24, 2007
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Posted: Tuesday, September 22, 2009 - 02:15 AM UTC
thanks for the replies everyone, useful stuff. Ive been looking at this some more and what i know think is that the primer ends up being thicker than some of the parts. I guess this makes the piece have more weight overall than the plastic can cope with...

When do you guys prime all the fiddly bits like landing gear struts? I have been spraying the complete sprues before i take any pieces off up til now. And also i have to prime things cos i brush paint with those revell aqua acrylics.

Rich