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Any paint sprayed from my airbrush doesn't seem to be setting hard.

GW's temple guard blue seems to wear off edges, Vallejos grey surface primer peels off and now the vallejo varnishes have just peeled off of my guardsmans shoulder pad. I figured that the varnishes are supposed to give a harder wearing finish over GW paint so I tested it on some old models. A few days after spraying I ran my nail across it to test the durability. The varnish broke easily and the whole shoulder pad covering peeled off, the old paint underneath (not airbrushed) wasn't touched when i did the same.

- The paints had been left to dry from anywhere between a day to a few weeks.
- I thin my paints will Vallejos airbrush thinner.
- I live in the UK and use my airbrush indoors with an extractor so I would imagine humidity / heat shouldn't be a problem.

Can anyone think of a possible reason for this or am I expecting too much from my paints?

You do get a very thin coat with an airbrush, so it can rub off easily if you aren't careful. How are you priming your models, and how are you applying the varnish? If you aren't using proper primer, that will be one possibility. If you are airbrushing the varnish, perhaps too much thinner to get it through the brush without clogging, or too few coats.

You can also give multiple coats of varnish if you want more durability.

If the primer is coming off thats a primer problem. Is this a old school metal model? Or by any chance did you wash the model to see if any release agent was left on it?

It's a comon problem that the Vallejo Grey Surface primer is not durable at all.

It chips and peals off almost like a dipcoat of rubber with little actual adhesion to its base surface. When I use it is usually lay down a thin coat of black primer, and go over it with the grey (the primer sticks to other primer and paint very well.)

As for the wearing issue, it sounds like you have very thin paint and varnish coats which will wear through semi easily with continued handling.

Ok thanks for that guys, it seems unanimous that the issue is too few coats of paint and varnish and Vallejo primer just isn't that great.

JamesY - I'm applying everything with my airbrush.

OgreChubbs - The models are plastic, I have never washed my models before painting. Does it make a noticable difference?

Washing can make a big difference. I've yet to have a problem with those I've not washed, but I've seen some mold release on some that needed to go. The mold release utterly rejects paint, it will really ruin your day

I wash everything after final assembly. Even the oil from your hands can screw up primer adhesion. I wash with soap and water then use latex/nitrile gloves to handle once painting begins.

How long are you leaving the primer to dry for?

Pretty much all you can do is...

Wash the model before use (use dish soap typically, sometimes I just spray isopropyl alcohol on the model and scrub it with an old toothbrush then wipe it off with a rag if I'm too lazy to go down to the kitchen and wash it with soap )

Use a good primer

Keep the model clean while working on it (avoid touching with fingers, wear gloves if necessary or mount the model to something so you don't have to touch it)

Apply a bit of varnish when it's done

Paint does have an optimum thickness, too thin and it'll rub off, too thick and it will gouge off easily in big chunks. When you airbrush you are typically on the thin side of the spectrum, but there's not a lot you can do about it other than being careful and finishing off with a varnish.

You could also swap to a tougher paint, but that's not a step most people want to take.

On the note of washing, can someone tell me why I wouldn't put whole sprues in the dishwasher at like 45 degrees C?

 Buttery Commissar wrote:
How long are you leaving the primer to dry for?

I normally give roughly 24 hours for primer drying.

 Buttery Commissar wrote:
How long are you leaving the primer to dry for?

The primer was left for well over 24 hours

Personally I find Vallejo PU primer largely useless. A primer on a plastic model, for me, has various jobs.

1. Provide a consistent colour to then lay your other paints on top.... Vallejo PU primer does that, but then so does any reasonably opaque paint, primer or not.

2. Provide a layer that can potentially be sanded back on larger vehicles, Vallejo PU primer doesn't sand well.

3. Provide a tough surface that sticks well to the model and in turn paint sticks well to it. Vallejo PU primer just does not adhere well and even after curing is far too easy to peel off.

So it only does 1 out of 3 tasks, the one that can be achieved by almost any other paint you pick up and put through your airbrush To top it off, it takes ages to cure as well.

What primer are you air bruising on skink?

kb_lock wrote:
What primer are you air bruising on skink?

At the moment I am using Gunze Mr. Surfacer thinned with Gunze Mr Color Self Levelling Thinner. They make various grit levels, I mostly just use the 1500 which comes in black or grey (and it's quite a light grey, similar colour to Vallejo's grey primer).

I understand that being lacquers, not everyone is going to want to use them. But they're tough, give a nice finish, are sandable, cover well and dry pretty quickly.

If I want a coloured basecoat without having to do a separate "primer" layer I've had pretty good luck using Tamiya acrylics thinned with Gunze Mr Color Self Levelling Thinner. They are reasonably tough (I guess because the Mr Color thinner is a strong solvent and bites well on the plastic), spray very smoothly and you can clean your airbrush with regular water and Vallejo's AB cleaner (if you try using water or Vallejo's cleaner with Mr Surfacer it will turn to goop, you need to use a lacquer thinner to clean up Mr Surfacer). I have no idea if the Tamiya acrylics are sandable, any time I've used them it's been in a place where I don't care about sanding.

I imagine spraying Gunze's Mr Aqueous Color range (alcohol based acrylics) with a lacquer thinner would give similar results to using Tamiya acrylics thinned with Mr Color as well, as they're similar paints but I can't comment because I haven't tried spraying the Gunze acrylics on bare plastic yet.

It'd be nice if there was an acrylic primer option, or just something that didn't have quite as much fumes as a lacquer, but I'm not aware of any such product. Acrylic rattle can primers often stick well because they also use very strong solvents but I'm not aware of an airbrush equivalent.

In ten years of airbrushing, I tried almost every brand and range (except Gunze, which I'm very curious about...).

Conclusion: the only airbrushed acrylics that have some durability are Tamiya. And this is sad, because Tamiya matte range isn't exaclty... colorful... almost half of it is made of grays...
I thin them with isopropylic alcool or ethilic alcool, but water is also OK.

I haven't a clear opinion about primers. Stuck with Citadel for decades, as well as other minor brands only available in my country, and I'm more or less satisfied.

What do you guys do with your models? O.o

I don't even varnish models unless I have to even out glossiness, and I have Imperial Guard from the late 80s that I still game with in pretty darn good condition. I mean, it's not like you actively go picking at your paint with a fingernail once it's done, right?

 Talys wrote:
What do you guys do with your models? O.o

I don't even varnish models unless I have to even out glossiness, and I have Imperial Guard from the late 80s that I still game with in pretty darn good condition. I mean, it's not like you actively go picking at your paint with a fingernail once it's done, right?

Even still since its water based paint.. once hands rub the models to much some of the paint especially the edges will start to come off.

 Talys wrote:
What do you guys do with your models? O.o

I don't even varnish models unless I have to even out glossiness, and I have Imperial Guard from the late 80s that I still game with in pretty darn good condition. I mean, it's not like you actively go picking at your paint with a fingernail once it's done, right?

Most my problems come when building, painting and finishing the models. Some models are easy, as you can avoid touching the model itself while working on it (mount it to a cork or the top of an old paint bottle). Other models there's no way to avoid handling the model while you're still working on it. You may also want to mask or weather certain models which is harsh on paints that aren't tough. One of the guys who frequents the local shop always tells me to swap to enamels when I talk about how another one of my weathering attempts went badly Enamels are nice but they have too many annoying idiosyncrasies for me to use them other than special occasions.

Once the models hit my display shelf or the gaming table I'm pretty careful with them and they rarely get damaged.

The other thing is paint does tend to toughen slowly over time, I don't know what the strength vs time curve looks like, but I know it's harder to damage the paint on a model that's been around for a year than it is to damage the paint on a model that has been painted a week ago. Since I don't tend to game with models that are hot off my work bench that probably helps as well.

@Skink - ahhh yes, fair enough. I agree: some models are tough to keep from handling, and that can be a problem with paint coming off.

I'm embarrassed to say, this is actually less a problem for me than occasionally putting paint on. Sometimes, I get paint on my left hand (thumb or something) and unwittingly plaster a thumbprint of paint onto my model. OMG, I hate that. If laser-eyes could kill! I paint most of my models in subassemblies, and when building them out, I typically imagine how I'm going to hold them, so as to minimize handling.

Also, you're most certainly right about the hot-off-the-press issue: over years, my models get more indestructible, to the point where even dropping them onto hard surfaces don't do much (except make the pieces separate sometimes). Like you, there aren't many models I own that go straight from paint table to game table.

@snoop - on metal models, I find this an issue if the primer hasn't totally baked on. On plastic models, though, it's only really the hard corners if they get a lot of handling during the paint process.

@ Talys - ya i hear you man! I rarely do that with the paint on my finger but I still know your pain!!!!!