Painting via vinyl paint mask

[flavinny]

 I am in the process of repainting a 3.5-gauge model of the 1403 Western Maryland 4-8-4 and looking for help from anyone that has used vinyl paint mask for lettering etc.
 I intended to somehow get paint from shaker cans that I could mix to match colors then airbrush over the mask. A friend suggested using acrylic paints available from hobby shops. I don't know if that would be waterproof. (This is a live steam loco water and steam all over the place)
 " How to" would be appreciated and help in getting the correct color paint also.

[peteski]

I often "decant" pain from spray cans to spray it through my airbrush.  There is plenty of info on how to do this if you search the Internet for "decanting spray can paints", or something similar.  But some of the methods are not very safe.  I  never puncture the can!



I simply change the spray nozzle to one on which I installed a plastic tube.  I have collection of various such nozzles as different brands of paint use different nozzles.  Then I just spray the paint out thought the nozzle into an empty glass bottle.  Carefully, as the paint will bubble as it sprays out because the liquid propellant (usually propane) in the liquid paint expands to gas. Once you have enough paint, screw the lid back onto the bottle, but to not tighten it as the propellant will keep on evaporating from the paint for few days.  Also do not shake the bottle as the propellant can bubble up.

Once all the propellant escapes, the paint will be safe to use.  This sounds like a hassle, but it isn't really that bad. As I mentioned, I do this fairly frequently.

[TrainCat2]

Been there done A LOT of that. I use vinyl paint masks all the time. They work great but have their limitation based on the paint chemistry you will be spraying. Don’t use hobby store paints. I am a scratchbuilder of of giant scale RC planes. We use Behr outdoor water based latex primer + paint all the time. It’s water proof on your house so why not on other items. The real trick is mixing the paint to a consistency of coffee creamer and spray very light coats. Not uncommon to spray +8 coats and use can use a heat gun or hair dryer to accelerate the drying process.

The mask composition must be selected for certain paints. With Latex, you can use anything. For solvent paints, using any mask material not specified for solvents will cause bleed runs due to the solvent eating the glue out at the edges. Oramask from Oracal is great for general purpose stuff but you have to select the tackiness correctly. Fresh painted undercoating will want a lighter tack while a fully cured undercoat can use anything. Stay away from Oramask 810, that all I’m gunna say bout that! For solvent paint, don’t cheap out and purchase the Avery Dennison SF 100.

[flavinny]

Thanks for the info TrainCat2.  Searching "decant" returned the info I needed. I intend to try to match colors of the prototype and do not want to run out of material. Some post suggested puncturing the can so that all content can be removed. You suggested not doing this. Have you emptied an entire can by spraying into a container?
  I have no experience using paint mask or using an airbrush. I inferred from your post light coats dried between coats yield best results. The mask I will be using is three parts (three colors). The first mask will have to stay in place to preserve the registration marks. Should intermediate mask be removed?
 Should paint be completely dry before removing mask.     

[Lemosteam]

Thanks for the info TrainCat2.  Searching "decant" returned the info I needed. I intend to try to match colors of the prototype and do not want to run out of material. Some post suggested puncturing the can so that all content can be removed. You suggested not doing this. Have you emptied an entire can by spraying into a container?
  I have no experience using paint mask or using an airbrush. I inferred from your post light coats dried between coats yield best results. The mask I will be using is three parts (three colors). The first mask will have to stay in place to preserve the registration marks. Should intermediate mask be removed?
 Should paint be completely dry before removing mask.   

The hole in the can may have been my thread.  I have done this many times with no ill effect or scary outcome, just a long "hiss" of propellant.

I find the spray nozzle decant method produces a lot of overspray while decanting into the container, this can be mitigated somewhat if a very small hole is drilled in the cap to allow the pressure to escape, but I find my method much, much cleaner.

There are three tricks to the puncture method-

1: Remove the nozzle and let the can sit still for at least three days in the exact place you intend to puncture the can (so you don't risk shaking the propellant when moving the can)
2: Do not move or shake the can before or while puncturing the first hole.  I use a carbide scriber pencil, no hammer, just hand pressure.  Additional holes can be added after depressurizing to allow for clean pouring
3: After decanting into a sealable container large enough to contain your expected volume- DO NOT SEAL IT- let it rest to allow any remaining propellant to escape, don't worry the paint won't dry.  After two days I wiggle the bottle a little with the loose cap to see if the paint gets agitated by any residual propellant.  If none then the container can be sealed.

Tamiya sells three sizes of empty paint bottles at my local hobby shop, and likely online.

There are some really good glass bottles with silicone sealed lids on Amazon that protect the paint really well.

[flavinny]

I am concerned about the paint I intend using (Rustoleum) attacking the vinyl or it's adhesive. I already have the mask cut from Ormask 811. I called Orflo product support and was told a solvent-based paint might leave a residue around the edges of the masked area that will have to be cleaned off.
 Has anyone experienced this, is it a problem? Product support recommended 810S.?

[TrainCat2]

I am concerned about the paint I intend using (Rustoleum) attacking the vinyl or it's adhesive. I already have the mask cut from Ormask 811. I called Orflo product support and was told a solvent-based paint might leave a residue around the edges of the masked area that will have to be cleaned off.
 Has anyone experienced this, is it a problem? Product support recommended 810S.?

As I stated, I used Oramask 810S and the adhesive was so light that it would not give a good seal causing the mask to peel up during painting. The surface must be mirror smooth to get a good seal. I can sell you a huge roll of 810S for next to nothing, but that is also what you would be getting. A couple of weeks ago, I posted pics of the Merchant’s Warehouse that was stenciled with Avery Dennison SF 100 using Rustoleum rattle can. Not a single bleed over DPM brick walls.

[flavinny]

Thanks, TrainCat2, I will post a picture when I get it done. Nothing can go rong.

[flavinny]

Disaster strikes.! My first attempt using the mask was a panel on the back of the tender which included the engine number and capacities. Good results. Next, I did the road name on the side of the tender. This did not go well the base paint lifted when I removed the mask. I did some things differently but do not know if this caused the problem. The side has rivets which caused me to be more aggressive burnishing the vinyl down.  Second, I used a hair dryer between coats, did this make the adhesive stick more? It did seem to be harder to remove.
   I now have to consider how to proceed, I dreed having to strip the side and repaint.  Any advice to proceed, techniques on how to work around surface problems such as rivets? 

[peteski]

Maybe the base paint wasn't fully dry?
What specific paints are you using, and what is your painting technique?

Do you use primer before the base coat?  When the mask lifted the paint, did it just lift the base coat leaving primer still on the model's surface, or lifted all the way to bare metal?

[flavinny]

I had stripped the original paint, went over it with 000 steel wool cleaned the surface with Dupont Prep-Sol, painted with Rustoleum Etching primer followed with Rustoleum Auto enamel.  Dried for several weeks. The paint lifted off down to the base metal.
  I am looking for suggestions on how to proceed. I am considering airbrushing the areas that lifted off. What might have caused the problem? Could the hair dryer affect the adhesive on the mask? Can excessive burnishing have an effect? Suggested technique for masking around rivets and other surface irregularities.

[peteski]

Well that seems to indicate that the primer did not adhere well enough to the metal surface. Few weeks drying to  me seems more than adequate.

Maybe the Prep-Sol did  not remove all the contamination from the metal surface?  Maybe the primer was applied too lightly (it was partially drying between the spray nozzle and the model surface? Or maybe simply the masking material's adhesive is too aggressive?  I have never used adhesive vinyl film for masking, so  I can't comment on that.