Surface Prep for Painting

I can well understand the frustration with lifting paint when removing masks. For years I have used the following method for prepping the surface, paint lift is a non issue now.

Real airplanes are painted using an "etch" to give the new paint a surface to bind to, the etch is sprayed, then finish coat is applied. These finishes must stand up to flight in rain and snow, at speeds of 450+mph.

To mimick that process, after a good alcohol wipe down is done to the model, I use a fine textured pad for polishing fingernails, available at beauty supply shops. (My wife buys them for me, I feel weird about going there.)

The best one I've found is A*S*P, called "Buff and Shine Block," two sided, one finer than the opposite. After cleaning I use the more agressive side to give a slightly satin look to the plastic, (it's still very smooth, not a deeply rough texture at all,) then with the finer side I go over the whole surface again. As final prep for paint, another alcohol wipe down. It's also helpful to use the thin vinyl gloves to avoid skin contact.

The buffing pads are only about $3.00, keep them clean and they last for a very long time, they wash up well with soap and water. The e-mail for them in Valencia, Ca. is starnail.com, they could likely tell you where they are available. Highly recommended by me, I really like them. Also great for polishing canopies, etc. 

Hope someone finds this helpful, happy modeling all.

Patrick

Sounds like you're doing everything right to me, Steve.

A real head-scratcher, this.

Greg

First off iSteve, don't you be name calling yourself over Testors poor choice of paint nomenclature! (MM Grey (or Gray) Primer). Not one of their finest moments, IMO.

So good on you for not mixing the Alclad with anything.

I'd be remiss in not asking what you thinned the Tamiya with. It should hang onto the Alclad well. (If shoulds and coulds....etc, etc).

One more thing, you mentioned you usually use Tamiya masking tape. "Usually" probably doesn't belong in that sentence. And I wonder, do you de-tack the Tamiya prior to using it? As forgiving as Tamiya is, I still de-tack it. Do you?

Just so you don't feel alone, my first acrylic paint job went like this: MM Grey Primer (you get to laugh at me, it's ok), followed by MM Acryl, and followed then by blue painters tape. Not a happy ending.

Thanks for the chuckle Greg!

I only thin Tamiya with Tamiya thinner (the "acrylic" one for their "acrylic" paints). I mix at about 2 parts paint to 1 part thinner. The Alclad primer usually gets at least 24 hours before I paint over top. I've had lifting problems with Tamiya primer as well, but that was Model Master acrylics lifting off the primer, so I'm not too surprised. I used to de-tack my masking tape before I used the Tamiya tape and stopped because the Tamiya tape seldom gave me issues, but I could do that too.

The project I'm working on now will be done in Alclad metallics (Moebius Nu Cylon Raider), so I'd be surprised if I have any lifting issues, but I'll take all the precautions anyways and see what happens.

Thanks again for all the help gentlemen. Please keep the suggestions coming if you got 'em.

First off iSteve, don't you be name calling yourself over Testors poor choice of paint nomenclature! (MM Grey (or Gray) Primer). Not one of their finest moments, IMO.

So good on you for not mixing the Alclad with anything.

I'd be remiss in not asking what you thinned the Tamiya with. It should hang onto the Alclad well. (If shoulds and coulds....etc, etc).

One more thing, you mentioned you usually use Tamiya masking tape. "Usually" probably doesn't belong in that sentence. And I wonder, do you de-tack the Tamiya prior to using it? As forgiving as Tamiya is, I still de-tack it. Do you?

Just so you don't feel alone, my first acrylic paint job went like this: MM Grey Primer (you get to laugh at me, it's ok), followed by MM Acryl, and followed then by blue painters tape. Not a happy ending.

isteve, Sorry to hear about your travails. I have given up on using dishsoap. There's just too much at stake. The only thing I use anymore is 91% ISO alcohol. It's hard to imagine how the primer couldn't stay down after a good cleaning with that stuff. I noticed you said the paint might have lifted off the primer. It sounds like you let the primer cure long enough, but I understand alclad can take a while to cure. I prime large surfaces with spray cans of Tamiya primer or Mr. Primer Surfacer. Yes, it's the more expensive way to go, but I feel pretty confident it will stick. I also do not spray on a thick coat of primer. I try to just barely cover the surface. Seems the thicker the primer coat, the less abuse it can take, as well. Maybe because it dries on the surface before it dries next to the plastic and traps in some of the gases? Beats me. Best wishes on your next project. Barrett

Greg

As Ernie and a couple other gents have mentioned, I can hardly imagine Alclad primer pulling up even if the substrate was slightly oily from handling.

Certainly do a wipe down with some ISO in the future, though. And BTW, MM grey primer is not primer. It is a color called "Grey Primer".

Did you thin or alter the Alclad Grey primer in any way? Was it mixed (stirred) well?

As Nathan mentioned, your best bet to figure this out is probably to do some serious testing before your next real paint job.

And I do hope you can keep us updated.  This needs to be sorted out for you, it's a big problem.

Indeed - it pretty much removed my Hurricane from any chance it had of even making it to the contest, let alone winning anything.

The more I think on it, the more likely it was that the primer stayed and the Tamiya lifted. BTW - did not know that about the Model Master paint. I just assumed Gray Primer meant it was primer. How stupid of me. The Alclad primer was well mixed as it now comes with the BB's in the bottle, and I check for an even colour in the paint before applying. I didn't add anything to it or thin it.

So this begs the question: how do I keep my Tamiya paint on my Alclad primer? Latex gloves are a start. What else?

As Ernie and a couple other gents have mentioned, I can hardly imagine Alclad primer pulling up even if the substrate was slightly oily from handling.

Certainly do a wipe down with some ISO in the future, though. And BTW, MM grey primer is not primer. It is a color called "Grey Primer".

Did you thin or alter the Alclad Grey primer in any way? Was it mixed (stirred) well?

As Nathan mentioned, your best bet to figure this out is probably to do some serious testing before your next real paint job.

And I do hope you can keep us updated.  This needs to be sorted out for you, it's a big problem.

Krylon used to be really good stuff, but they have been messing with the stuff for several years now, and it is not that good any more.  I have now switched to the Rustoleum "Painters Touch" stuff.  Duplicolor has an okay spray can primer, too.

For what it's worth, my go-to primer is rattle can Rustoleum primer. Never had issues with them at all. Krylon brand primer and paint has been banished from my home forever. They're crap.

These days most kits seem to be free of mold release, but some still are contaminated with it.  Fortunately, lately I have been warned by others about those kits.  I also find resin stuff much more likely to have some residue than styrene injection molded stuff.

i do nothing but wipe off dust from sanding, prime with vallejo primer and paint. Never a problem. The problems I have encountered are in the paint and thinner and the drying time allowed, not the surface.

Thank you everyone for your comments and suggestions - please keep them coming if you think of anything else.

Plastic Junkie - yup, MM primer is pretty useless in my humble opinion. It has failed me every time once the masks come off. I too was surprised when the paint lifted. That's why I thought contaminates from my hands (ie - oils). When I think about it, i may have actually run my hands over the areas where it lifted to ensure a smooth finish of the primer. So probably the primer stayed, but the topcoat lifted.

Wilbur - very sound advice. The only thing I would change is wiping the alcohol with a lint-free cloth rather than cotton balls, pads or swabs to ensure no little fuzzies get left behind. I've got a small micro-fibre cloth lined up for the job.

My next project starting this weekend is the Moebius Nu Cylon Raider (I alternate between sci-fi and real aircraft), which will be done in pretty much all Alclad primer and finishes. Considering it's all lacquer, I shouldn't run into any lifting from masking, but I'm not taking any chances anymore.

I can only give my experience over 30 years.  Wash all parts in warm water and dishsoap.  Rinse thoroughly. Usually let dry overnight.  Use an enamel primer coat (I have always used MM Camo Gray airbrushed). Let dry for at least 3 days from final priming. Then Tamiya Acrylic topcoat and let that cure for at least 3 days. before handling. 

One thing when I start building If my hands get anything on them I go to the sink and wash them, then back to work.  Always start work with a hand wash to get the oil off them. When the build is done, I usually wipe off the raw styrene with alchohol and cotton balls on the day I spray the primer coat. I don't go crazy with the wipedown but it does get the styrene really clean.

Not being in a rush and letting paint cure-out does wonders.

That is unusual specially with a solvent type primer that gets a good bite into the plastic. I know that MM Acryl Primer will lift very easily when removing masking material.

The only possible cause for the adhesion failure could be either bad primer or the plastic surface was contaminated by something.

No idiot proof solution I'm afraid. You can do everything right and paint will still sometimes let you down. I don't use alclad primers. Are you sure they are lacquers? I know they have some enamels, which take a few days to dry fully. I only say use 99% IPA because it is a  stronger cleaner and it evaporates in seconds. Just experiment with a few different methods and techniques and see what works for you. It helps to have a scrap model to use for testing. Then go ahead and try out masking tape and see if your paint is lifting off of your test piece. 

The Hurricane plastic is gray, so it was difficult to tell whether the primer lifted or not; I can't remember if it lifted or not on the previous kit. When you're furious, it's hard to remember details sometimes.

The primer should have had enough time to cure - at least 24 hours though more likely 48 or more. The paint only lifted in areas I know I handled often; in other areas of the models I had no problems at all. Has anyone had problems with Alclad primers? My presumption is a lacquer primer will generally give the best adhesion. Now that I think about it, I think the previous model was primed with Tamiya from the can.

Does it make that much of a difference whether I use 99% or 78% alcohol?

I really want to beat this issue. I spent an awful lot of time on that Hurricane and had hoped to enter it in my first contest only to have it go to pot because of a crap finish on my paint job. Does anyone have a 100% idiot-proof solution to ensuring a lift-free paint job? Because evidently I'm an idiot.

I think what's happened is you didn't let the primer cure completely. I know I usually do wash the sprues before priming but there are others that don't bother and never had issues of primer/paint peeling off - even after masking. 

Is the paint also removing your primer? Or is the primer staying bonded to the plastic? If its the latter, it means your primer is failing you, and is not giving a good surface for your topcoat to adhere to. You could scuff up the primer after it cures and see if that helps the paint bite into it. But yes, always wipe down your plastic with 99% alcohol because it cleans the best and dries up really fast, leaving no residue. Tamiya acrylics usually bond nicely when thinned with their own thinners or IPA.