Model Railroading > Painting resin? Apparently, i can't

I am playing with a couple big dawg shells and the paint won't stick.  I've painted tons of plastic shells with no issues, but with these, any small bump or scratch causes the paint to flake and peel right off.  One is painted with badger acrylics and the other with testors enamel.  I guess i need some kind of primer to get the paint to adhere correctly?


What do i need to do?
 

Possibly a light grit blasting to give the resin some tooth and a good scrubbing with dish detergent to remove oils from the release agents.

Doug Wetherhold
Macungie, PA

Resin!  This is where our love for Chinese manufacturing of our lower productionrun models comes in and we thank them if they've built our/your model of choice.

Resin could be very inconsistent and it depends on what they used, how they poured it and how it was mixed.  I had some cars done by a fellow and one car painted fine and they other one, no matter how I treated it, cleaned it it ; the paint wouldn't stick in certain spots.

You really have to be wary with resin as some came from back yard operators and others could be very professional.

Maybe try cleaning the model with turpentine.  Try not to let that get on your skin though.

Rick

Pick up some Comet dry power cleanser (or some other type of dry powder abrasive cleanser) and use it with generous amounts of water and a toothbrush to scrub the model.  This not only removes the oils and release agents, but since it is an abrasive cleanser, it also lightly scours the surface to give the paint something to hold on to.

Brian

After cleaning like mentioned above, try a can of Adhesion Promoter, usually in the auto/spray paint section. I've used it mainly on automotive interior parts and some exterior pieces.

Posted from Android

You can see where the paint peeled off and i tried to touch it up.  It just made it worse.  Gotta toss this thing in a bucket of alcohol, strip it clean and start over.  


I am out of grey paint though....  lol

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This is where solvent based paints helped. The solvent would also etch the resin to help hold. Also the mold release agent was not an issue either. Truscale paint might work since it is a solvent based paint. My experience has taught me to use solvent based on resins.

The word 'resin' here is pretty meaningless. There are many types of polymer or plastic (resin) and these models will be made from one of them. If the polymer selected was a poor choice such as polyethylene or polypropylene then paint will not adhere well without a lot of priming and effort.
However, i suspect that the polymer used is more likely to be a polystyrene based one, in which case the problem is more likely to be some residual mould release agent left on the polymer after manufacture. As someone else stated, this type of contamination needs removing with a solvent or detergent prior to painting.
Surface preparation is key when it comes to painting.

There's another possible scenario as well. Off gassing.  Again without knowing the particular polymer involved, it's tough to make a call.

i was involved in trying to attach polymer-based product labels to industrial polystyrene shells a while ago. They looked great after placement but developed bubbling blisters after a week or two.  

So hydrocarbon cleaning might be a mixed blessing, it may cause the same problem to appear later on.  Another solution although maybe not practical is to place the shells in a vacuum chamber for a day or two, or in a sealed, dry container with a desiccant suitable for hydrocarbons. 

I know guys, probably not practical, but if all else fails...

I'd be careful tossing it in alcohol to strip the paint.  I melted a Kaslo SDF40-2 shell trying that...  Grit blasting is probably a better choice.

Nathan Beauheim
Cheyenne, WY

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I have read your posting and thought I'd answer since I've made models containing ten resin castings that I made from materials
purchased from Micromark. I made a master, a rubber mold and then duplicate castings.  The completed model is washed in soapy warm water,
then dipped and brushed in Floquil Plastic Prep (I don't think it is currently made)  Then a coat or two of Floquil primer, 2 coats of Bright Silver,
then a clear coat.  Decal the model and another 1 or 2 coats of clear coat. I have experienced no problem with the 3 dozen or so cars that
I have built and sold.  I guess Solvent paint may be the reason I did not experience the peeling problem, at least it is worrth looking into.
Scalecoat 2 is a currently available solvent based paint for plastics.

Hope this solves your problem!
Frank30

I'd like to offer some help with this problem. I have been rubber molding and cast resin and painting resin for close to 40 years in my job and in the hobby. It is a reliable method of making reproductions of models. For one I have found best results using commercial grade resin products and not hobby grade stuff. The material I use is a commercial grade polyurethane resin. It is durable plastic and best used with solvent based products as I state on the header of the package that the shells, cabs and parts come in. I highly recommend washing the shell with either mineral spirits or in extreme cases lacquer thinner ( this I recommend with the plastics I use and not others that I am not familar with ). I soak the shell in a bowl or container while I use a tooth brush or small brush to wash surface well ( inside and outside )and then left to air dry. This is common practice in most model shop paint shops use and I recommend it here in this case. Remember in any painting oils from our hands and silicones in the air can cause paint problems and that is why most high end paint shops are closed paint booths where the air is filtered. We know that we don't have those conditions in the average modelers paint area so understand we should be aware of what's going on around us. I offer these tips when using my castings to minmize problems you have with paint my product. I have had a lot of years of using resins and found they can be a useful product in the hobby. I'd like to take this time to thank those that have tried our products and always be clear that if you have a problem with either painting , or any other function using the product to please contact me so I can help you to solve the issue. I am more then happy to help with solutions or if it's an issue with the material or a flaw in the product doing what is necessary to resolve the issue. I read to many times where there is a simple problem where it could be resolved so easily with an e-mail or phone call but will be air on a forum where opinions are given that may or mostly may not resolve the problem and possibly create more issues. I ask please contact me that's why I put on the front of the package my contact info so if there is a problem to let me know because I know my product and am really the only person who can do something about it. So please in the fiture give me a chance to solve the problem. thanks Bruce from BDO

BigDawg Wrote:
-------------------------------------------------------
> I'd like to offer some help with this problem. I
> have been rubber molding and cast resin and
> painting resin for close to 40 years in my job and
> in the hobby. It is a reliable method of making
> reproductions of models. For one I have found best
> results using commercial grade resin products and
> not hobby grade stuff. The material I use is
> a commercial grade polyurethane resin. It is
> durable plastic and best used with solvent based
> products as I state on the header of the package
> that the shells, cabs and parts come in. I highly
> recommend washing the shell with either mineral
> spirits or in extreme cases lacquer thinner ( this
> I recommend with the plastics I use and not others
> that I am not familar with ). I soak the shell in
> a bowl or container while I use a tooth brush or
> small brush to wash surface well ( inside and
> outside )and then left to air dry. This is common
> practice in most model shop paint shops use and I
> recommend it here in this case. Remember in any
> painting oils from our hands and silicones in the
> air can cause paint problems and that is why most
> high end paint shops are closed paint booths where
> the air is filtered. We know that we don't have
> those conditions in the average modelers paint
> area so understand we should be aware of what's
> going on around us. I offer these tips when using
> my castings to minmize problems you have with
> paint my product. I have had a lot of years of
> using resins and found they can be a useful
> product in the hobby. I'd like to take this time
> to thank those that have tried our products and
> always be clear that if you have a problem with
> either painting , or any other function using the
> product to please contact me so I can help you to
> solve the issue. I am more then happy to help with
> solutions or if it's an issue with the material or
> a flaw in the product doing what is necessary to
> resolve the issue. I read to many times where
> there is a simple problem where it could be
> resolved so easily with an e-mail or phone call
> but will be air on a forum where opinions are
> given that may or mostly may not resolve the
> problem and possibly create more issues. I ask
> please contact me that's why I put on the front of
> the package my contact info so if there is a
> problem to let me know because I know my product
> and am really the only person who can do something
> about it. So please in the fiture give me a chance
> to solve the problem. thanks Bruce from BDO


So far, i really like your products. Great way to get a locomotive that's only available in brass or not available at all. The DD35 is coming along well. I just suck at paint prep and painting.

Posted from Android

Well there is so much to learn about when it comes to painting and if in any way I can help I would be more then happy to do so. If it's something I do not know I know enough people in the hobby that do custom painting I will ask around and find you an answer. Keep pluging away I have seen some of your work and it is very creative and clean so you have a natural talent. We all never know everything and there always some other way or a new and better way to do things. Bruce

https://www.bigdawgoriginals.com/pages/photos 



Edited 1 time(s). Last edit at 07/22/16 20:22 by BigDawg.

The DD35 is definitely fun to toss together.  Working on handrials and decals now, then i am going to figure out how to power it and make it DCC compatable.

Now, if you would just build an accurate SW1001 with a 4 window cab that i can stuff on an athearn frame, all would be good.  

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I'll second that SW1001!!

I've added it to my list to do projects , thanks