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Major Paint Issues
Joel_W
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Posted: Monday, April 15, 2019 - 07:36 AM UTC
I've never had this issue before, and have absolutely no idea how to deal with it.

Two of the three body sections have imperfections in the plastic. They look like lines that go right through the plastic shells. I use to think that they were caused by impurities in the liquid plastic as it was injected into the molds. I've had them appear from time to time, but lacquer primer has always covered them. That is until today.

I've reached to stage of painting the BT18. So I cleaned all the parts with Iso Alcohol, and air dried them.

I primed the body shells with Mr. Hobby 's Mr. Finishing Surface Primer1500 Gray, and thinned it 50/50 with Mr. Color Leveling Thinner #400. I applied the primer with my Grex Genesis air brush with a .3mm setup @ a flow rate of 16 psi. Two light coats, and then two heavier coats. I let this dry for 24 hrs. I then very lightly wet sanded with a piece of Tamiya 3,000 sponge. Those lines were still there but less noticeable, so I figured that they disappear with the color coats.

My next paint session was applying the color coats. I always air brush my color coats with my other Grex AB that has a .5mm setup, at a flow rate of 16 psi. As usual the paint used was Gravity pre-thinned lacquer, and it was a new bottle. Two tack coats, then two heavier color coats, with the last coat being a wet coat.

The lines are all still visible. So now I need to strip all three body assemblies and start over, which I've never had to do before. What's the best method for stripping the lacquer paint? And how do I deal with those lines in the plastic?

Joel
Merlin
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Posted: Monday, April 15, 2019 - 08:02 AM UTC
Hi Joel

That sounds a real pain! You could try a paint stripper to remove what you've done so far. Looking at what's available in the US, I see Testors do one:

https://www.testors.com/product-catalog/testors-brands/model-master/primers-top-coats-thinners-cleaners/paint-and-decal-remover/

I have filled imperfections like you describe by using enamel paint as a filler - brushed on the area in layers and sanded smooth, but it takes time because the paint shrinks as it cures and the flaw reappears.

I have better results with superglue mixed with a little bit of talc - thin enough that it will flow into the imperfection. It doesn't shrink so much, and adding the talc means the filler is closer to the density of the surrounding plastic, so it's easier to sand level.

I've got to say, though - with a kit like this, I'd be tempted to request replacement parts from the manufacturer/importer.

All the best

Rowan
Joel_W
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Posted: Monday, April 15, 2019 - 08:36 AM UTC

Quoted Text

Hi Joel

That sounds a real pain! You could try a paint stripper to remove what you've done so far. Looking at what's available in the US, I see Testors do one:

https://www.testors.com/product-catalog/testors-brands/model-master/primers-top-coats-thinners-cleaners/paint-and-decal-remover/

I have filled imperfections like you describe by using enamel paint as a filler - brushed on the area in layers and sanded smooth, but it takes time because the paint shrinks as it cures and the flaw reappears.

I have better results with superglue mixed with a little bit of talc - thin enough that it will flow into the imperfection. It doesn't shrink so much, and adding the talc means the filler is closer to the density of the surrounding plastic, so it's easier to sand level.

I've got to say, though - with a kit like this, I'd be tempted to request replacement parts from the manufacturer/importer.

All the best

Rowan




Rowan,

I guess I didn't explain the issue correctly. those lines go right through the plastic like it's a different color, but there is no ridge, no indentation, nothing to feel, let alone fill.


I had this with my Ebbro 72E, but since I painted it black, those lines didn't show.


Joel
Joel_W
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Posted: Monday, April 15, 2019 - 09:51 AM UTC
Major Update,
I decided to help the X20-A along and started to work all three body parts with a piece of #600 emery cloth, and those lines were gone as I must have ruffed up the surface enough. I checked the inside and they were still there. So, I went over the surfaces with a piece of .3,000 sponge, and now the surfaces are all smooth with no molding shine, and so far no lines that I can see!!

Tomorrow I'll go over all the sections again, and if I don't see any sign of those lines, I'll re-prime with Mr. Hobby 1500 again, and go from there.

Just knew that the modeling Gods would find away of testing me, as the BT18 has been a true joy to build so far.

Joel
md72
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Posted: Monday, April 15, 2019 - 02:57 PM UTC
Based on my limited experience with injection mold tooling, my guess is that some impurities, not polystyrene, were left in the barrel of the tool and were injected along with the rest of the plastic. Since they weren't polystyrene,they're not taking paint like PS. Probably why sanding and black paint his the issue.

I have a bottle of the Mr.Surfacer 1500, how do you work with it?
AussieReg
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Posted: Monday, April 15, 2019 - 10:39 PM UTC
I have had issues with old Revell kits in the past with the swirling patterns in the plastic. It almost seems like there are varying densities of plastic at the surface and they take and reflect the paint differently. Iím really glad that you managed to overcome the issue even though it took a fair degree of extra effort.


Quoted Text

I have a bottle of the Mr.Surfacer 1500, how do you work with it?


Thin it with at least 50% lacquer thinner and airbrush at 15-20 psi. It is the best micro filler and primer that I have used so far.

Cheers, D
md72
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Posted: Tuesday, April 16, 2019 - 04:27 AM UTC
Kewl, thanks. Now I'm thinking of using it to prime my F9F-8 before I do a GSB final coat.
Joel_W
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Posted: Tuesday, April 16, 2019 - 05:10 AM UTC
Been trying to get on the site, but it's been down, so I weeded and mulched the main front bed. Boy, was that fun

Damian, your view that the line represents two different consistencies, coupled to Russell's point of view that the line is the demarcation between two different pours as one ran out, and the next liquid Plastic emulsion was added. They must have been made from different Plastic pellets loads.

Anyway, I finished up the polishing with water and a piece of Tamiya 3,000 sponge. Still no line, so I went ahead and primed all 3 body shells. Came out absolutely perfect

Joel
Joel_W
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Posted: Tuesday, April 16, 2019 - 05:19 AM UTC
Mark,

As for the Mr. Hobby 1500 primer filler, Damian is 100% correct as to the proper procedure. However, like everything else in our hobby, their primer comes in 3 grades. 1,000 which I equate to Tamiya's Gray Primer sealer, and I use it strictly as a filler as it has the coarsest pigments. 1,200 is next, and can be used as a filler for small cracks and scratches as well as a primer. It's pigment seems to be finer then 1,000, but courser then 1,500. When I prime with it, I thin it 2 parts primer to 3 parts LC. 1,500 is the thinnest, and is strictly a primer. I try to use 1,500 as my go to primer as it has the finest pigments, and thinned 1:1 with Mr. Hobby #400 LC, it lays down smooth as silk. One thing I do is to use a tack coat, wait a few min, then a heavier coat, and finally another heavy coat if need be.

Joel.
Merlin
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Posted: Tuesday, April 16, 2019 - 07:52 AM UTC
Hi Joel

I'm still trying to get my head around the issue! I guess I must have simply been very lucky because, while I've seen plenty of swirls over the years (actually, one was so bad it actually did cause an indentation that needed filling!), I've never had a case of the plastic simply taking paint differently across the surface of a part (unless there's been mould release agent causing mischief).

To be honest, I very rarely even bother with primer except on vacuforms and resin kits, or unless I've done extensive filling and sanding like my forlorn MGB.

But, getting back to the weird phenomenon you've hit, I wonder whether a coat of Klear/Future sprayed first as a "primer" would seal it? It might be worth an experiment if there are any areas you haven't sanded.

All the best

Rowan
md72
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Posted: Tuesday, April 16, 2019 - 08:13 AM UTC
Joel, I'm quite familiar with Mr. Surfacer 500 and 1000. I usually use both as final fillers on problem surfaces. Never actually used either as a full on all over the model surface primer, it's so thick, I never thought of airbrushing it. Does it matter if I'm using Leveling thinner or regular thinner?
Joel_W
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Posted: Tuesday, April 16, 2019 - 08:48 AM UTC

Quoted Text

Joel, I'm quite familiar with Mr. Surfacer 500 and 1000. I usually use both as final fillers on problem surfaces. Never actually used either as a full on all over the model surface primer, it's so thick, I never thought of airbrushing it. Does it matter if I'm using Leveling thinner or regular thinner?




Mark,
I totally forgot about 500. It's fantastic for small filling jobs, but I never considered it as a primer since it's so thick.

Right now I'm 100% 1500 for a primer. thinned 1:1 it's just the best I've used to date. Dries smooth and real fast.

My go to Lacquer thinner is Mr. Hobby #400 leveling thinner. I'm not sure what they add to it for self leveling, but it does seem to make a difference compared to my old standard Tamiya Yellow Cap. I still use it for anything and everything except exterior surfaces. I've got a full 250ml bottle that I need to use up.

Joel
Joel_W
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Posted: Tuesday, April 16, 2019 - 08:53 AM UTC

Quoted Text

Hi Joel

I'm still trying to get my head around the issue! I guess I must have simply been very lucky because, while I've seen plenty of swirls over the years (actually, one was so bad it actually did cause an indentation that needed filling!), I've never had a case of the plastic simply taking paint differently across the surface of a part (unless there's been mould release agent causing mischief).

To be honest, I very rarely even bother with primer except on vacuforms and resin kits, or unless I've done extensive filling and sanding like my forlorn MGB.

But, getting back to the weird phenomenon you've hit, I wonder whether a coat of Klear/Future sprayed first as a "primer" would seal it? It might be worth an experiment if there are any areas you haven't sanded.

All the best

Rowan



Rowan,
Like you, this is the 1st time that those swirls have ever caused me any issues. But from now on, I'm going to remove them by polishing the surface so I don't have to go through all of this again.

I just got into the primer about 4 years ago, and liked how it handled as you said, fillers, and bright colors like Yellow, Red, Green, cover much better over primer then applied to raw plastic. Of course, with Gravity, Zero, and MCW paints, you need a primer coat. Both for coverage and to protect the plastic from lacquer paint. Those paints are true Auto lacquers, so you gotta be real careful.

Joel
md72
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Posted: Friday, April 19, 2019 - 03:19 PM UTC
Well I tried it. Worked very well.


I started with a 1:1 mix with Mr. Color Self leveling thinner. it was too thin and just blew off of the surface. I emptied the cup and just ran the 1500 straight out of the bottle. Used my new Badger 105 Arrow with 0.5mm tip. Got a few splatters, but it worked really well.
Joel_W
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Posted: Saturday, April 20, 2019 - 12:39 AM UTC

Quoted Text

Well I tried it. Worked very well.


I started with a 1:1 mix with Mr. Color Self leveling thinner. it was too thin and just blew off of the surface. I emptied the cup and just ran the 1500 straight out of the bottle. Used my new Badger 105 Arrow with 0.5mm tip. Got a few splatters, but it worked really well.



Mark,
I'm glad that the Mr. Hobby 1500 primer worked for you, as it's the best I've tried to date. Your F9F Panther does indeed look perfect in a primer coat.

What PSI were you shooting at that caused all the splattering? Gravity, Zero, & MCW automotive specialty modeling lacquer paints come pre-thinned to the consistency of water, that I AB @ 16 psi with a modest paint flow. To high of a PSI and to much paint will indeed splatter. The key is light, consistent coats, slowly building up the primer to whatever level you want.

Joel


md72
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Posted: Saturday, April 20, 2019 - 02:13 PM UTC
Thanks Joel. The air compressor is part of the problem, I used my 'artists' air compressor. It's a badger 80-2, with no regulator or tank. It's so old that the manual isn't online. I think it's 2cfm and maybe 23psi. And the 0.5 tip really blows out the paint. One of these days I'll get a new fuse for my primary compressor.
Joel_W
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Posted: Sunday, April 21, 2019 - 12:42 AM UTC

Quoted Text

Thanks Joel. The air compressor is part of the problem, I used my 'artists' air compressor. It's a badger 80-2, with no regulator or tank. It's so old that the manual isn't online. I think it's 2cfm and maybe 23psi. And the 0.5 tip really blows out the paint. One of these days I'll get a new fuse for my primary compressor.



Mark,
I see. Without being able to regulate the PSI, you're forced to modulate the amount of paint/primer:thinner ratio, and vary your distance to the model surface. The further away you need to be and get, the more the paint will dry before it hits the surface. To close and you get splatters, runs, and what nots.

I certainly would either get a regulator for your current compressor, or a fuse for your main compressor, and either way would solve your air brushing issues.

Joel
md72
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Posted: Sunday, April 21, 2019 - 03:11 PM UTC
Well Joel, thanks for your confidence. With a lot of luck I'll find the right size fuse and get back in business.