Painting ABS plastic

[Parkesy]

Hey everyone, I got my sons grasshopper built for him and the building side of it went really well for my first time back! But the painting side was a disaster!!!! I’ll post a finished result up and fill in the details to what went wrong, but basically I’ve started all over again using a dulux acrylic (just a sample pot of house paint) and currently applying a few coats of it with my air sprayer. What sort of time frame should I give before spraying an enamel clear coat? Some say as soon as it’s dry, others say wait 24 hours?? It’s 27’ Celsius and sunny in Melbourne today so the acrylic coats are touch dry in 10 mins. And will an enamel clear coat be fine over acrylic?? It’s a British paints clear coat paint and prime satin finish. Thanks for any tips and advice! 

[Juggular]

I'm just tossing an idea out there because I haven't done it myself... but artists varnish their acrylic paint after a week. Some do after 6 weeks. 

Where you are is warm and dry so that should help greatly.  But I would wait at least 48 hours or 72 hours just to be on the safe side.  I'd have a fan blowing on it, if I want to do it in 24 hours.  

People do paint enamel over acrylic on miniature models soon after painting with acrylics.  But that's more like a wash (thinned black enamel to accentuate dirt in nooks and crannies).  Very little black enamel stays on after it dries, allowing acrylic to dry even after that.  What you plan to do is encasing the whole thing.  If acrylic isn't completely dry, you may get a crazed surface weeks later, as acrylic fumes try to break through the enamel surface.  

I'd test out in a small area under the body first.  Good luck.  

 

[WillyChang]

As a pretty general rule, DO NOT PAINT ENAMEL OVER ACRYLICS!! 

On odd occasions the enamel won't wreck the underneath paint but it usually ends in tears.

Acrylics can go onto enamels, but better to not mix types & brands.

Why are you using housepaint anyway? Just get a rattlecan of any gloss paint from SuperCheapAuto/Bunnings/RejectShop for $3 if you don't want to buy proper model paint (Tamiya TS paint is best). 

[Juggular]

Oh, I missed on the house paint part... I must be going senile... 

House paint is not good.  There is a lot more pigment than solvent.  They will flake off the plastic body.     

 

[Parkesy]

I used house paint because I had such bad results from enamel spray cans it put me off them. It could have just been the brand because I’ve never had problems before with them, or maybe it was just too hot when I was spraying. And also to get paint for my spray gun in a small tin the only choice was a sample pot from the hardware. Not ideal I know  I should have just made the drive to the lhs and got a Tamiya can. I always thought enamel over acrylic is fine, but not the other way around? I didn’t think acrylic will stick to oil based paints, but it will bond fine to acrylic? 

[Parkesy]

Ps on a positive note I’ve got another body on order so this is going to be his bashing body and will save the new one for the future 

[Parkesy]

So it seems the solvents in enamel will likely eat into the acrylic underneath. I went to the hardware and about the only thing I can think of to try is BondCrete watered down to the suggested dilution ratio to use as a sealer. I used it often as a builder and it’s a great product, basically just like PVA and it dries clear. 

[Pumesta]

I just use car paint on my hard bodies. prime, colour, and clear

[Juggular]

1 hour ago, Parkesy said:

I always thought enamel over acrylic is fine, but not the other way around?

Both are fine...PROVIDED that both are completely dry.  At least, that's my understanding.  

I build model kits.  In the order of pigment density, the ideal situation is that you use lacquer first, enamel next and then acrylic.  But often, modelers use acrylic first because it's just so easy to use. Then use enamel as a top wash, to make tanks and airplanes look dirty.  Kit builders pour enamel thinner with a few drops of black in it, on models already painted in acrylic.  This is possible because enamel does not dissolve acrylic paint (or visa versa).  

However, "encasing" is different.  If acrylic isn't completely dry, the alcohol in acrylic will try to break through the surface of enamel coat.  The key is how dry it is. If it's really dry, you don't even smell it.  Then there is no solvent left, all you have is pigment. Covering that up with enamel should be fine.  But even acrylic won't dry in 1 day.  

Don't use BondCrete over acrylic. If you can mix water or alcohol to dilute, it's an acrylic product.  Acrylic will dissolve acrylic: just like pouring water on watercolor paint. 

Besides, using BondCrete is like eating salad with a pitchfork.  A regular kitchen fork would work better.  Building materials like house paint or Bondcrete are crudely made to cover up imperfections on large immobile things.  BondCrete used under tiles or stucco doesn't have to be mirror smooth.  Neither is wall paint.  But you would notice a fine hair stuck on a Grasshopper body.  It's just different class of materials.  But, modelers do use floor coat on cockpit canopies, because it can give you mirror smooth surface.  

 

[Lightningrc]

Just get a tamiya spray designed for abs bodies and just light coat it on .

do not use enamel spray paint !!

you can use car paint but it will need a coat of plastic primer , then normal primer then the paint .

go and get the right spray and you will find it easy .

 

[Parkesy]

Thanks Juggular, but I’d jumped the gun and gave a watered down sealer coat of BondCrete to it already  

It’s dried pretty quickly and I’m starting the decals now. The paint job was really dodgy as it is after using an electric wire brush to strip the old spray paint so lots of gouges and scuffs. I’ve kinda looked at this as a learning curve and conceded defeat on a pristine finish. It should come out good enough for my 5 year old and I reckon he’ll have it well and truly trashed in the next few weeks, so I’ll save the spare body for a future restoration!

[Parkesy]

15 minutes ago, Lightningrc said:

Just get a tamiya spray designed for abs bodies and just light coat it on .

do not use enamel spray paint !!

you can use car paint but it will need a coat of plastic primer , then normal primer then the paint .

go and get the right spray and you will find it easy .

 

Thanks mate. I learned my lesson the hard way this time unfortunately  Next time I’ll just getting everything from the LHS and know that I’ve got the right materials for the job 

[Lightningrc]

No problem , just make sure to get the correct spray from ur model shop .

one is for the clear bodies and you want the paint type for Abs body’s.

most don’t need a primer just scrub the body with fairy liquid and a green pad to etch the surface and let dry first .

[Parkesy]

On 02/01/2018 at 11:23 AM, Lightningrc said:

No problem , just make sure to get the correct spray from ur model shop .

one is for the clear bodies and you want the paint type for Abs body’s.

most don’t need a primer just scrub the body with fairy liquid and a green pad to etch the surface and let dry first .

I made the drive up there today to get a new Servo for the Fox and saw all the correct Tamiya paints and couldn’t believe how cheap they were. Even cheaper than the wrong stuff I bought from Bunnings! I got a little 10ml clear x-35 as they said it’s fine for over decals and helps seal them down? I brushed on one coat and still have plenty for a few more coats on the next project. A small airbrush is on my shopping list now too. 

[53HRA]

Normal real car paint in a spray can works the best in my opinion. If you are in the UK, Halfords car paint is brilliant  

[Lightningrc]

If ur gonner use normal cat paint like said it’s worth getting a can of plastic primer also .

yes it will work just using standard primer but plastic primer eats into the plastic to form a bond 

[racer1]

I'll second the fact that regular old automotive paint is a much better option than the hobby grade stuff. Here in the states we have access to Duplicolor auto paint in literally thousands of colors and it's great quality. Just pick your color and spray it. 

There are also a number of clear coats to allow you to have whatever finish you want. Super gloss, Semi, flat etc.  

As for using different types of paint.  I generally try to stay away from this but I have found that Duplicolor has a clear Enamel that lays down ultra smooth and it's easy without runs etc. 

The Rule is Enamel over Laquer is OK. Even knowing this. I typically wait at least a week before spraying clears.  I also always spray on a couple of very light coats of clear to test for a reaction before applying decals. After that I apply the decals and apply several very light coats to cover the decals. My final coat is medium heavy to get the desired gloss finish.  After about a week you can wet sand and polish if desired. 

[WillyChang]

Downunder the auto parts shops sell Holts Duplicolour touchup cans.

But they're often stale old stock & sometimes have lost their pressure from age.

Plus pricewise they're A$15-19ea... I might as well buy real Tamiya PS/TS for A$13-15ish.