Spray Paint problems

[cbargs]

Hi everybody,
So here is the problem. I have a mold of a stormtrooper helmet I sculpted with Rebound 25. I use smooth cast 300 to cast plastic helmets. When it is time for painting, I run into this problem shown below in the picture. Craters form and I have now idea why.

First I would follow this order of operation
1. spray mold with mold release
2. cast helmet
3 wash helmet with methyl ethyl ketone to get rid of mold release residue.
4. Wash helmet with soap and water
5. Primed helmet.
6. 24 hrs later Light sand with 320 grit sandpaper
7. wash and dry helmet.
8. Paint.

Got craters still. So I Changed things a bit.
1. used baby powder to coat mold
2. cast helmet
3. Sand with 320 grit sandpaper so the paint can stick
4 wash helmet with dawn soap and water
5. Wore latex gloves to carry the helmet in the garage to paint. I did this so the oils on my skin won't cause craters.
6. Paint and still craters!!!

I've been bashing my brains to figure out how am I getting a containment on the helmet to cause these craters. Any help from you very awesome professionals will be a great help to me. Thanks for your time.

 

[JOATRASH FX]

What temperature are you painting at? Might be it's too cold. Or you're laying on the paint too thick (looks like it in ht photos- do a few very light coats first). Or the air is too humid. Or there is static electricity in the plastic. Some primers need DAYS to cure, despite what is says on the package. (Example, Plastikote paints require that you spray the next layer of paint or primer either withing an hour OR after 72 hours- if you do it too late or too early it crackles!)

 

[Irken Tech]

The "cratering" is called Orange Peel. Maybe searching for that term will help but it sounds like you are doing things right.

 

[laellee]

How is the primed surface looking after that dries? Are you still getting an orange peel on it, or is it coating fairly well at that stage? Are you using the same stuff to prime and paint? I noticed your pics of the paint+primer cans, I assume that you'd be getting the same effect showing up on your first coats then.

I've used plasti-kote's sandable primer as my base on 300 casts, and haven't had any problems.

 

[DatSteve]

I'm not super experienced in this department quite yet, but I see you're using a 2 in 1 spray can paint/primer. Those can yield fairly poor results depending on the surface their trying to cure to. Maybe try a higher quality primer and knock it down with the 320, followed by paint. If a spray gun isn't available, I would almost prefer a brush on primer, just be careful not to glob too much on. I've used bullseyes 123 primer and had good results, as well as a Lowes Generic fast drying primer that you can sand after 15-20 minutes. Good luck. The casts look great

 

[Dynofiend]

Not trying to slate your painting technique, but on the images you provided it looks like you have saturated one area (and got total coverage) with thick passes of the can.

Do you do a few very light coats a good while apart (IE even after two or three coats you can still see the white underneath) or do you hit it quite hard and get total coverage while the previous coat is still wet?

If I'm way off here, you could try painting something else (like something else made of plastic, storage box or something) with no prep at all, and see if you get the same effect. If you do, you know it could be the paint, or your technique that's off, rather than the molding/prep process you have messing with the paint.

 

[cbargs]

What temperature are you painting at? Might be it's too cold. Or you're laying on the paint too thick (looks like it in ht photos- do a few very light coats first). Or the air is too humid. Or there is static electricity in the plastic. Some primers need DAYS to cure, despite what is says on the package. (Example, Plastikote paints require that you spray the next layer of paint or primer either withing an hour OR after 72 hours- if you do it too late or too early it crackles!)

The temperature in my garage was 65 degrees at the time. I did apply 3 light coats and still got orange peel. So I got frustrated and just caked it on. Thanks for the tip.

- - - Updated - - -

The "cratering" is called Orange Peel. Maybe searching for that term will help but it sounds like you are doing things right.

Thanks for the correct term. I'm googling away right now.

 

[cbargs]

How is the primed surface looking after that dries? Are you still getting an orange peel on it, or is it coating fairly well at that stage? Are you using the same stuff to prime and paint? I noticed your pics of the paint+primer cans, I assume that you'd be getting the same effect showing up on your first coats then.

I've used plasti-kote's sandable primer as my base on 300 casts, and haven't had any problems.

See thats the puzzling thing about it. When I spray the primer it goes on great with no orange peel. Then I sand the primer with 320, give it a soap scrub, let dry, then apply the paint and boom, orange peel. I have used all rust-oleum 2X ultra cover products.

Thanks for the tip on plasti-kote primer. I will give that a try tomorrow for sure.

- - - Updated - - -

I'm not super experienced in this department quite yet, but I see you're using a 2 in 1 spray can paint/primer. Those can yield fairly poor results depending on the surface their trying to cure to. Maybe try a higher quality primer and knock it down with the 320, followed by paint. If a spray gun isn't available, I would almost prefer a brush on primer, just be careful not to glob too much on. I've used bullseyes 123 primer and had good results, as well as a Lowes Generic fast drying primer that you can sand after 15-20 minutes. Good luck. The casts look great

Thank you. I am going to find some plasti-Kote sandable primer tomorrow and give it a shot.

 

[cbargs]

Not trying to slate your painting technique, but on the images you provided it looks like you have saturated one area (and got total coverage) with thick passes of the can.

Do you do a few very light coats a good while apart (IE even after two or three coats you can still see the white underneath) or do you hit it quite hard and get total coverage while the previous coat is still wet?


If I'm way off here, you could try painting something else (like something else made of plastic, storage box or something) with no prep at all, and see if you get the same effect. If you do, you know it could be the paint, or your technique that's off, rather than the molding/prep process you have messing with the paint.

Hahah yes, I blasted it trying to get the orange peel to go away. Before my frustration breakdown I applied 3 light coats and still the orange peel came. Once I tried painting with the same spray paint and techniques on a scrap piece of ABS plastic and it went on like butter. Which makes me believe that it hast to be something with the smoothcast 300.

 

[lurch]

I am not familiar with the plasti-kote line of primers. but the primers I have used do not resist water. It might be possible the primer absorbed some moisture and released it during the application of the paint. might try blowing off the job with clean air then wiping it with a tacky cloth to remove the dust instead of washing. The tack cloth would be available from an auto paint supply shop.

 

[Chrgr440RT]

I used to get this every once in a while when I didn't make sure the paint was well mixed and warm. Now I put my rattle cans in a tub of hot-ish water (not too hot mind you) for about 15-20 mins before I paint. Then I shake the holy bejeezus out of the can. And I mean shake it good. I usually go for about 2-4 mins instead of the 1 the can says. Multiple light coats and I'm golden.

Also, if I do need a primer I stick with Tamiya SuperFine spray can primer. Its a little expensive, but dang it goes on smooth.

Hope this helps and don't give up.

 

[laellee]

I used to get this every once in a while when I didn't make sure the paint was well mixed and warm. Now I put my rattle cans in a tub of hot-ish water (not too hot mind you) for about 15-20 mins before I paint. Then I shake the holy bejeezus out of the can. And I mean shake it good. I usually go for about 2-4 mins instead of the 1 the can says. Multiple light coats and I'm golden.

Also, if I do need a primer I stick with Tamiya SuperFine spray can primer. Its a little expensive, but dang it goes on smooth.

Hope this helps and don't give up.

+1

I float my aerosols in the sink too, it's amazing how much it helps the application (especially after bringing them in from a cold trunk lol). They also shake out easier too. Especially helpful with texture paints too (that's where I learned about that first)

 

[JOATRASH FX]

It might be possible the primer absorbed some moisture and released it during the application of the paint.

Exactly- especially if scrubbing with soap (which shouldn't be necessary). 18 Celsius (about 65 F) should be ok for most spray paints but warming it up a few degrees is preferable. (Most will need 15 C to cure at with anything close to acceptable results.) Try a tackcloth a suggested, of dry-wipe and brush off the dust. You CAN also use a bit of isopropyl alcohol to dampen the cloth as it will evaporate quickly, but use sparingly because acrylic-based paints will sometimes dissolve with it.

 

[SithApprentice2]

Cratering usually means lack of adhesion to the surface you're spraying and the likely culprit (as others have noted )was likely due to the water based wipe down to remove dust before spraying.

Let us know how it turns out.

 

[cbargs]

Fellas,
Thanks for the overwhelming responses and tips. I didn't think a newb like me on this forum would get so much help. I am going to give this another shot after work. Good thing I casted plenty of spares. I am going to skip the soap bath and go right to sanding with 320 and giving it a wipe down with a tack cloth. I am worried about about this because I read once that when 300 cures, it leaves behind oils. We shall see I guess. I brought in my paint cans from the garage so they will be at room temp., but I plan on giving them a hot bath and shaking the living **** out of them before spraying. Wish me luck and thanks again for all your help

PS.

It might be possible the primer absorbed some moisture and released it during the application of the paint. might try blowing off the job with clean air then wiping it with a tacky cloth to remove the dust instead of washing.

So many dirty things popped in my head when I read this. Thanks for the help buddy.

 

[lovelyandy]

could be that your sanding your primer too smooth.

I've had troubles applying paint to surfaces I've sanded to glass smoothness and the paint just has nothing to stick too, in one case i've got something that the paint has still not dried after 4 months, still tacky to the touch.

i'd recommend trying sanding your item, primering then painting straight on to the primer and then sanding your paint and touching up and areas you've got a problem.

Good luck & keep us posted

 

[jasonw2112]

Orange peel, is when the paint goes on and dries, but the surface, looks like the surface of an orange



Solvent pop, can be caused, in several ways. In your case, it could be caused by putting too much paint
on the surface, with out letting each coat dry. So the solvents in the paint, try to escape. Causing what
looks like spots.



Than there are fish eyes. This is caused by the surface not being cleaned properly. It's like the paint just goes
around the pant in circular patterns.



Now! I think your problem, is your spraying to much paint, in between coats. Not letting it dry, so the solvents
are trying to escape. This can happen even in light coats! Weather it's to cold, or not. I would guess your using
enamel paints. They can cause this problem, when there is not enough heat, and sun, to provide the paint to cure fully.

If anything, go out and purchase Lacquer spray paint, and this will help solve this problem. Lacquers dry much faster, allowing
the paint to cure. But, you still need to put it on in light coats, letting it sit and dry in between. Until you get a nice smooth
finish.

If you have to use enamels, put on light coats, and sit the piece next to a space heater (Keep an eye on it! Paint is Flammable!)
This will help the paint cure, in between coats, when there is no sun, or summer heat availble

 

[JOATRASH FX]

Not also that washing the raw casts is still a good idea, just not after it's got primer on it.

 

[acesh007]

Good info thus far. Make sure you washed the helmet before you apply any paint and let it dry. If you still have issues, vinegar is another good thing to wipe down the helmet with and let it dry.

Only other thing is make sure your paint is warmed up and mixed well.

 

[cbargs]

If you have to use enamels, put on light coats, and sit the piece next to a space heater (Keep an eye on it! Paint is Flammable!)
This will help the paint cure, in between coats, when there is no sun, or summer heat availble

Will using a space heater and/or a heat gun work as long as I'm not roasting the paint?