Trouble with paint

[Haggis9444]

Hello.

I'm am currently building PCM'S excellent Spitfire XIV again.

I have just spent ages on the nose, painting, sanding, applying decals.

its painted with Humbrol 90 acrylic.

I have just sprayed it with a top coat of Halford clear lacquer and the paint has cracked all over.

I have used Humbrol acrylic paints before with this spray and never had a problem.

Any ideas?

[Chuck1945]

How long did you wait before applying the clear? What you describe sounds a lot like what happens if acrylic layers haven't thoroughly dried (not just dry to the touch).

[bentwaters81tfw]

That's a bummer when it happens. How long did you leave the paint to dry/harden off before overspraying?

I tend to seal everything down with Klear and let it harden for a few days before a matt coat. I've never used Halfords clear lacquer before. maybe that is the problem rather than an acrylic varnish.

[Haggis9444]

The paint was applied over a week ago.

I wet sanded it 2 days ago.

I also thoroughly wiped it down with kitchen roll before spraying.

I'll sand it back down and try again.

[Parabat]

You might be better off using Mr Muscle oven cleaner to remove the paint without fear of sanding away details etc.

Then you can just start again. Sorry to hear about it, but it might be best to use an acrylic clear coat over acrylic paint to be safe.

[Haggis9444]

Mr Muscle??

[Parabat]

http://www.amazon.co.uk/gp/aw/d/B000TAUMGI?pc_redir=1413087695&robot_redir=1

Sorry, a brand name. I guess any proprietary foaming oven cleaner will work. Get a clear plastic bag, put on gloves, spray your model with oven cleaner, pop it in the bag, spray some more oven cleaner in and leave overnight.

Remove the model, use an old toothbrush to gently remove any paint gloop and rinse it off thoroughly.

[Haggis9444]

Sounds fantastic.

will give it a try.

Thanks.

[old thumper]

I would never use automotive paint or lacquer on models, it is just too strong. If you don't have an airbrush and don't want to buy expensive Humbrol spray cans then maybe try Pledge multi-surface wax (formerly known as Klear) which Sainsbury's sell in a big bottle for a few quid, you can just paint it on and it doesn't leave brush strokes as it is self levelling.

Personally I would airbrush on enamels and then airbrush on humbrol gloss cote followed by matt cote.

Edited October 21, 2014 by old thumper

[cruiserguy]

Hi Haggis,

I am sorry to hear what happened, but I concur with Old Thumper about automotive paint and lacquer. I just don't understand why people use them when there are so many other good products on the market specifically aimed at modellers.

Moreover, you might find the lacquer hard to remove. There's a thread further down about Halfords automotive paint, and one contributor says it's the devil to remove once it's on and cured. However, I hope you don't find it's the same with the lacquer finish, and whatever you use removes it.

Best Wishes,

Will.

[Caerbannog]

Maybe the oven cleaner will need some more time to disolve the Humbrol as it is covered with Halfords clear (which will probably be quite resistant to the cleaner). I guess the oven cleaner will make its way through the cracks though. Maybe you will have to sand down the clear coat to the Humbrol layer and then apply the oven cleaner. There is a stuff called "Paint Killer" which works nice on Tamiya paints. It is more expensive but removes the paint immediately. I am not sure how good it is on the Humbrol acrylic though.

Rene

[viscount806x]

Hi Haggis, I am sorry to hear what happened, but I concur with Old Thumper about automotive paint and lacquer. I just don't understand why people use them when there are so many other good products on the market specifically aimed at modellers. Moreover, you might find the lacquer hard to remove. There's a thread further down about Halfords automotive paint, and one contributor says it's the devil to remove once it's on and cured. However, I hope you don't find it's the same with the lacquer finish, and whatever you use removes it. Best Wishes, Will.

Hi Thumper & Haggis,

Just a couple of words in reply and by way of rebalancing your views on automotive products - no offence intended chaps.

I've used Halfords paints for years for generic stuff like priming or whites and silvers, alongside all sorts of 'proper' model paints and do feel that the paints you dislike most definitely have their uses - as somebody else said recently, for starters they come in at a quite advantageous price alongside the dedicated modelling products. Indeed though, you do have to have a bit of nous when it comes to overcoating one type of paint with another, for example cellulose over acrylic or even enamels, i.e. not recommended but the other way around is fine, i.e. cellulose underneath.

On a related note, I have also found that automotive clear lacquers beat both Microscale Decal Film and Klear hands down for top coating home made decal sheets after printing.

Nige B

[old thumper]

The problem I have with automotive paints is that they can melt into model plastic, some thinners can do the same thing as well. My motto is if in doubt leave it out, I would hate to ruin a perfectly good and possibly expensive model.

[Caerbannog]

OK a bit off topic but I agree with Nige that automotive paints have their uses in our hobby. I use automotive filler/primer and it works great (so great that after repeating filling/sanding you run out of seam lines...). For some vivid colours I think the range supplied by the usual suspects is a bit limited. I sometimes use automotive spray cans or also those small repair bottles with a little brush in it. You can also mix these colours and thin them (Acetone works on those I am using).

I think the melting issue can be avoided by first using a primer coat and second by building up the paint in thin layers so the solvents which might attack the plastic can evaporize before they do any harm. At least I never had a problem. The last coat can be thicker to create a smooth surface (but usually the surface is already smooth). As Automotive paint is tough you can polish it quite nicely without rubbing it down to the plastic base.

The only downside is to get rid of the paint once it is cured. Maybe those airbrush erasers or airbrush sandblasting guns will work here?

Rene

[TPReggie]

I can vouch for the oven cleaner as I have very recently had to do the same thing - see my build here for photos of the oven cleaner stage.

http://www.britmodeller.com/forums/index.php?/topic/234968963-eduard-me110c-148/

Only thing I would warn you of is to make sure that you are very careful around areas (such as the cockpit) where you do not want the paint removed. If you let any of the cleaner get in to those areas it will strip the paint in there as well.

I put it on, spread it with the toothbrush and left it for a minute to eat into the paint and the paint off extremely easily with minimal scrubbing. I also kept a large container of water nearby to regularly clean the toothbrush.

After everything was off I cleaned the model with non-fragranced baby wipes, and then kitchen towel. A pain, but all went well and worked without issue.

[alan1302]

The problem I have with automotive paints is that they can melt into model plastic, some thinners can do the same thing as well. My motto is if in doubt leave it out, I would hate to ruin a perfectly good and possibly expensive model.

I've never had that problem with any automotive paints I've used in the past - I build car kits so tend to use rattle cans although moving over to an airbrush now. I'm assuming you had primed the plastic first?

[cruiserguy]

Hi Viscount,

No offence taken, it's just another point of view.

Best Wishes,

Will.

[old thumper]

I've never had that problem with any automotive paints I've used in the past - I build car kits so tend to use rattle cans although moving over to an airbrush now. I'm assuming you had primed the plastic first?

I haven't used car paint on models since I was a kid, maybe the stuff then was stronger than the stuff you get today. I have had one or two problems with thinners more recently, some thinners softens the surface of the plastic while other thinners leaves a funny white powder. The trouble with thinners etc is that it doesn't often say on the bottle just how strong it is or what it based on.

I would say to anyone using oven cleaner be careful, I melted my finger nails cleaning my oven a few years ago, the glove had split without my noticing.

[Steve Noble]

The problem is the Halfords clear lacquer. It shouldn't be used over Humbrol Acrylics because it's solvent based and too strong, that's why your paint cracked. If you used it before and it didn't crack you were very lucky.

As for non use of automotive paints in the hobby, well sorry guys, but that made me chuckle a bit. They only melt plastic if you don't prepare the surface correctly with a good quality primer coat. Do that and they are fine. The best thing about them is the speed at which they apply and dry. Also how tough they are and their resistance to handling, fingerprints etc. They also polish incredibly well and don't fade or lose their gloss over time. Most so called "model paints" do not compare, so much so, that I've switched over to using automotive paints, clears and lacquer model based paints exclusively now, and don't go anywhere near the regular hobby paints anymore. You guys that seem to be averse to using them should try the "new breed" of paints, I'm sure you'll be pleasantly surprised by them..

[Steve Noble]

Forgot to add, an overnight soak in isopropyl alcohol and a scrub with an old toothbrush should remove the Halfords clear without issue and, most importantly, will not damage the plastic at all