I hope you all had a Merry Christmas and are looking forward to the new year
So I have been painting my enginehouse, prepping it for assembly, and i have noticed that the paint is having a really hard time sticking to the surface (I am painting a Pikestuff kit FYI). By sticking I mean the the paint will not show through the bottom surface only if I glob on a substantial amount. I donāt want to do this really because I have details I want to show through. Originally I thought it was because I was painting over wall sections that oil paints with acrylics, and then some parts I had not handled carefully and I thought I might have got finger oils on them. However, last night I was painting parts I have never touched and the paint was still not sticking. I am using Tamiya paints so its not like I am using cheap quality paints or anything.
Have you folks run into similar problems? If so, how can I remedy this frustrating issue?
Even if you have never touched a part, plastic should be thoroughly clearned in a mild detergent for paint to adhere (or as a long ago boss of mind used to say, adhese) properly or at least reliably. That is because a mold release agent is often added to make it easy to remove the plastic injection molding from the mold itself. And of course the part you have never touched might have been touched by several folks at the factory ā just as people donāt want a car made on a Monday or Friday, just maybe your kit was created right after lunch or after a jelly donut break!
Needless to say the plastic needs to be thoroughly dried after washing.
If you are using a Tamiya rattle can to paint your kit (and in my experience a Tamiya rattle can paint can come pretty close to airbrush quality, without the control of course ā you are right about the quality) then I find they need to be VERY thoroughly shaken. When I am painting using a rattle can (which I generally do outdoors rather than in the paint booth ā and yes to fend off remarks I do own a good airbrush and good paint booth) I try to shake it for a good three minutes before use. Shaking for 15 seconds like I have seen some guys do can result in poor coverage just as you describe.
Sometimes even with every precaution it seems like paints have a hard time sticking to very very smooth plastic. In that case a quick blast with a rattle can of Dullcoat ā donāt overdo it ā might provide a good tooth for future layers of airbrushed, brushed, or rattle-canned paints. A light scrubbing with a very fine grit emery cloth or similar abrasive might also give you the tooth you need, but then you have the bits of material to deal with. that is also where a thorough cleaning comes in.
I have used Soft-Scrub and a toothbrush to wash parts with before painting. Since Simple Green can be used as a paint stripper for plastics (if left soaking in it) that should also be a good cleansing agent.
Wow Dave thanks! That was incredibly helpful I unfortunately do no spray my parts but rather paint them by hand however I try to ensure the paint is mixed as well as possible. But I was not aware of the mold in the plastics so I will give the parts I paint a good soak and scrub and if they are still being a pain, a quick blast of dull coat to give it some adhesion
Just as was said earlier, wash them well with warm water and mild detergent. Thereās all manner of stuff on them. Mold release agent, skin oil, etc. I had the same problem with some resin vesicle castings recently. I have another set of them to do now and Iāll be washing them first thing.
I agree that washing plastic or metal parts (basically, anything cast in a mold) is an essential pre-painting step.
I use warm water and dishwashing liquid for mine. Make sure you donāt handle the parts with your bare hands after painting. Use latex or cotton gloves.
We just had a thread on this same topic about a month ago ā try searching āpaint not stickingā in the āSearch Our Communityā box below the ad stack on the right of your screen.
I think this was the first time this was mentioned in the thread. Once I wash the parts, they donāt get touched with my bare hands until itās ready to place on the layout; sealed with Dullcote.
Could you guys please quantify this āMold Releaseā thing. I have worked in the plastics injection molding industry for 20 years and have never seen it used. The company I work for has 25 injection molding machines and we never use it. In fac,t in all the years in the business I have only ever seen 1 can of the stuff. The most likely problem is the glossy surface of the part which will not allow for the paint to flow and get a tooth on the surface. This finish is similar to the glossy finish on a new car. The paint will bead up water even without a coat of wax. After a couple of washings the surface opens up and allows for the water to flow. The best method to paint these parts is to wash them with a mild abrasive cleaner which will open up the surface a bit and allow for better paint adhesion. As for several people in the factory handling the partā¦ I doubt it. The parts are auto ejected from the machine onto a conveyor and transported to a worker who packages them. So, I would think that there may only be one person who handles the part.
This subject gets brought up a lot. Thats a good thing to see, it shows people are building stuff. Be careful with the gloves you use. Cotton will leave tiny hairs that could ruin a pain job and poor quality laytex gloves may have powder on them. Iāve built hundreds of model cars over the years and Iāve always used good laytex gloves or dishwashing gloves if I can find them in my size. The key to a good paint job is the prep work before hand. A good primer is HIGHLY recommended, it seals the plastic and helps the paint stick to the body better then if you didnāt use it.
As to gloves, a good point is made about powdered latex gloves ā avoid. It seems they are the easiest to find on sale of course.
For our purposes we do not need medical level gloves, so the household types (remember the old TV ad āSo flexible you can pick up a dime!ā) should be fine. After a period of use the gloves themselves can be lightly washed. If you can find a good deal on nonpowedered latex gloves however you can find them quite cheap in quantity. You may want to learn first if you have an allergy to latex.
As regards mold release agents I agree is is more commonly encountered on resin kits, where it is nearly universal, but it is also seen on plastic parts, particularly from smaller manufacturers. In any event there is no reason to assume a plastic part was kept in sterile conditions up until it was packaged ā a cleaning is always good practice.
I guess i would also encourage our friend the original poster to at least explore Tamiya rattle can paints if he can find the shade or color he wants in a spray version. Donāt ignore their military colors for example.
If you can spray with a wide sweeping motion (hard to do with a spray booth, easier to do outside) and really shake that can before use ā and yes, hold the can upside down and clean out the nozzle afterwards) it is surprising what good quality results you can get particularly on the large surfaces of a structure. That is also how I paint my Walthers plastic street pieces.
I also hand paint some of my plastic models to get more of a paint aged look. However, before I do, I always āprimeā the model by spraying it with a flat gray from a rattle can. This adds tooth to the surface and works better for me. The rattle can is not actually a primer paint, just some color of flat gray from Testors or Model Masters.
