Spraying with rattle cans

Model Railroader General Discussion (Model Railroader)
1

I’ve sprayed enough models over the last fifty years that I don’t think I should even have to ask these questions, but I need to try something different. I recently sprayed a small plastic building following all of the usual recommendations - wash the model to remove finger grease, handle it carefully, spray light coats, allow to dry, etc. After a few days, I masked some of the side walls with blue painters tape that was not pressed down extremely hard.

When I was done painting the other color, the tape pulled off some of the first coat. I was using a Rust-Oleum brand paint. This is not the first time this has happened recently, which has me wondering if I should try something different the next time.

If you go into a store and just buy a can of hobby spray paint labeled as “primer” I’m not really sure it’s all that different than light gray spray paint. But I noticed that Rust-Oleum has a variety of special primers (as does Kylon), such as Universal Bonding Primers, Adhesion Promoters and Plastic Primers. Have any of you tried any of these? I don’t really want to mess with an airbrush for some of these small models, but I need to figure out something.

I’ve also wondered if anyone has ever tried lightly sanding the surface of a brick wall to improve adhesion. I’m open to any suggestions.

I know paint formulations have changed over the years, but that’s a whole other topic. I just have to figure out a better way to work with what is available now.

Jim

2

I’ve never used rust oleum but i have had good luck with model master i get it from hobby lobby. my nebraska locomotive (profile pic) it was my first custom paint project i used tape and a liquid tape or paste to cover the white and i fog or mist the red to help with minimal paint bleed then i shoot it with 1 or 2 more heavier coats I give it a day or 2 to dry then peel the tape and paste off. just finished painting a coal tower with a rattle can and looks smooth.

3

Degreasing and cleaning the plastic parts with a product like Simple Green + warm water will help with paint adhesion. Some people will share their secret formulas. There is, or at least was, a product on the market called “Plastic Prep.”

Tamiya makes some spray primers that are actually primers. Others are primer-colored paint which may not do anything for paint adhesion.

4

I can’t really comment on spray cans, because I airbrush my structures, but the paint shouldn’t be lifting with the tape. If I have to mask something, I use regular masking tape, first applying it to my glass work surface.After smoothing it down tightly onto the glass, I use a sharp blade and straightedge to remove at least 1/8" off the edges of the tape, at least the edge which will be at the colour separation. This is to remove the normal nicks and dings that the roll accumulates while it lays around waiting to be used. In addition, the edges often pick up dust and fuzz, and the adhesive near the edges can dry out, lessen its ability to hold tightly to the surface being masked. The application to the glass does reduce the stickiness slightly, but usually not enough to allow bleed-under.
Once the tape is in place, and the edge burnished a bit to give a good seal, go ahead and paint.

As soon as the paint is dry to the touch, remove the tape by pulling it back on itself at as acute of an angle as possible - this lessens the strain on the paint to which it’s been adhered, and that decreases the chance that the paint will be lifted.

I suppose that you could try sanding the surface before the wash and rinse step, but only flat surfaces would be easy to do…a wall representing clapboard siding, or worse, novelty siding, would be a tedious job. You’d need to be careful with brick walls, too, so as to not lose the mortar lines.

Wayne

5

How much paint came off? It sounds like the paint stuck to the tape better than the plastic in some spots. As Wayne said, don’t let the paint completely dry before you remove the paint.

FWIW, I never use Rustoleum because it comes out to fast and thick for my tastes, so I can’t speak to its adhesive properties or variations. Krylon is thinner, IMO. They make a brand called FUSION which is supposed to be better for plastics, but I find regular Krylon to work well.

6

I have used both regular Krylon and Fusion. I havent checked the cans, but I try to get the one that is formulated for plastics. Quick drying and I have had minimal problems with paint adhereing to tape. When I do, I just touch it up by spraying paint on a piece of cardboard and using a brush to apply it to the problem areas. Usually you have enugh work time some that the paint does not dry on the cardboard. Can get messy though.

7

I don’t think I explained it too well the first time. I sprayed the whole brick building a light brown and let it dry. Then I lightly covered the walls with wide strips of blue tape so that I could spray the cornice a different color. When I removed the tape it pulled off some of the intitial color in small spots, not the second color for the cornice. So it wasn’t a matter of painting leaking under the tape or pulling off the tape before the second color was dry.

What I probably should have done was use paper to cover the walls with only a small bit of tape along the edges, but I never thought the lightly applied tape would pull off any of the base coat.

Jim

8

Jim,

Rattle can user…I am Not…but the below, works for that also…

One step that many people don’t do when prepping for a paint job without primer…(and to even scuff before the prime coat)is to scuff the surface they are painting…not sanding mind you…scuffing. It does not leave any marks what so ever like sand paper will. Even after primering, I always use a ultra fine scuff pad before putting a color dust coat on prior to full color painting…especially if you want a high gloss shine to the finish coat. Scuffing will make the paint grab better. I use products made by Mirka, some what cheaper than 3M, but works just as well since I’ve been using them in the 60’s. I always bought all My supplies by the case…cheaper that way…plus although I don’t paint full size cars/trucks any more, I have enough supplies to last a life time…for Me anyway!

https://www.autobodytoolmart.com/mirka-mirlon-total-scuff-pads-p-15894.aspx?gclid=CjwKCAjwnLjVBRAdEiwAKSGPIy8G6Y1u8N6sgQESgUZ8XhmsvQlx4tXc_5Ag0YRzcveTd6bh6aRr-RoC4RIQAvD_BwE

Take Care! [:D]

Frank

EDIT: I also never, never use masking tape/blue painters tape for color blocking separation, way too thick. I only use 3M fine line tape and have never run into a problem. I use the blue painters tape as a filler, between the fine line tape or body blocking paper for large area’s.

9

For plastic i always use an automotive “self-etching“ sandable primer. Just a light dusting coat, sand smooth and paint. And i avoid Rust-oleum paints for hobby use also. Blue painters tape leaves too rough of a break line in my opinion. I paint model cars also and use a thin pinstripe for a clean paint line and mask off the rest from there.

10

I agree about the rough break line, but this wasn’t anything fine. There was a lip in the cornice that I used for an edge to mask. I would normally cut the edge of the tape with a straightedge to get a new sharp masking edge.

The model turned out okay after I did some touch up work. I was making it for one of my surgeons since he was intrigued with what we make. I put his name on it so that he could display it in his office.

Jim

11

After you washed the model, did you wear gloves or use anything to protect the plastic from touching your fingers? It doesn’t take much to contaminate an area to cause your issue. Also, I’ve had experiences where washing, drying and never touching the plastic with bare hands still resulted in some paint not adhering in some places.

Not all paints are compatible with plastic (or wood, metal, etc).

Terry

12

No, I only handled it using some bracing I glued on the inside. And, I wasn’t eating potato chips, french fries or KFC at the same time. [:D]

Jim

13

Jim,

How long did you let it dry before you applied the masking tape?

14

nice comeback! [(-D]

15

I think I let the paint dry for a day or two. It seemed pretty dry when I masked it. It came off in tiny spots all over the building, which is what seemed so odd. If I was going to keep it, I could have weathered it since it looked like some random bricks here and there were peeling.

Jim

16

I’ve had both bleed under blue tape and paint pull off. One trick is to paint again on top the tape with the color you are masking so the bleed is the same color. (cutting a fresh edge and burnishing the edge also help)

Tamiya makes a really nice tape that neither pulls paint off nor allows bleeding. It comes is various widths, yes it costs more. For my modest construction efforts it is worth it.

17

Jim,

Good to hear you’re working on something for the surgeons, rather than vice versa.[tup][Y]

As others noted, Rustoleum can go on rather thick, but it is manageable with a little practice. Locally, it’s available in more colors and types in rattle cans than Krylon is, but if you can find it in what you need, Krylon works very well, thank you, and is more controllable in spraying.

I’ve also noted really variable drying times for Rustoleum, depending on the color and type of paint. Many colors dry rather well and quickly. If it’s one of the colors that has the 24 hour drying time, then the tape may have lifted it because it wasn’t quite as dry as you expected it to be. I’ve been caught a time or two with similar issues and have found that I need to read the label of each can to be sure I know what it needs in drying time.

If you want to try a different primer, I do recommend the Rustoleum Universal Binding Primer. I’ve actually not used it much on models yet, but have been using it for many other tough to prime surfaces, including plastic. It’s similar to the Tamiya primers and is nicely controllable while making a very thin coat. It will certainly help with what you’re experiencing here.

18

If you can smell the paint clearly it isn’t dry yet. Also, I have pulled up paint with the tape in situations where I let the tape stay on the model far too long. I now remove any tape or masking as soon as I possibly can.

Dave Nelson

19

Acylics cure, they do not dry and will feel dry to the touch in short order using flat paints, but this is not cured!!! Depending on where you live and time of year, it could take a week to fully cure. I never wash my models and only had this problem when I didn’t let the paint cure, but sometimes I wanted to get on to the next step.

20

I do a mixture of can and airbrush painting frequently, so here are some bits of advice:

3M Scotch Brand makes a 1/2 inch masking tape that is for “professional use”. I use it in masking all the time and get clean separations between colors.

There are other types of detail masking tapes with different tack levels- some of these may be available at commercial auto body supply stores in your area or definitely on line. I keep a few of these types of masking tapes around for insurance, if I feel I’m not getting a good mask.

Always follow the cleaning prep with dish detergent - rinse well with cold water and pat dry, then let the model air dry before masking.

Get those blue disposable nitrile gloves $5/100 at Harbor Freight- keeps you and the model clean!

If painting yellows or oranges, use a WHITE primer coat first - if no white primer, use flat white. Other colors darker than yellow or orange can use light gray primer. There is a difference in appearance that makes the yellows and oranges more vibrant and no thinning issues at corners on the model when using white primer first. Occasionally, I also use white primer with medium and light blues as well.

When masking, don’t rely on the tape edge for your line- use an Xacto blade and a metal ruler to cut your own edge- I lay a length of tape on a tempered glass cutting plate (Michaels Crafts- a few dollars) rather than cutting on a “self healing plastic mat” to ensure a clean edge is obtained.

Don’t rush the masking process - it’s a hobby, not a production job on a schedule. You may send 80% of your time prepping and masking, but that makes for a good job. Nothing is more frustrating than having to redo a paint job.

Plan ahead- use gloss paints and , if spray cans, check to be sure- satin spray paints are not a suitable base for decals- or cover with a clear gloss after before decaling.

Don’t rush! (part 2) - I give each paint color at least 24 hrs t