Acrylic Paint spraying advice

[John B (Sc)]

Help - advice please.

I am trying spraying acrylics.

Have sprayed enamels and cellulose for a few years. Every time I spray acrylic onto a plastic model, it blobs. Doesn't seem to want to smooth out.

I'm using Model Color, thinned with water and a little IPA. The models are washed lightly with soapy water to ensure no grease, allowed to air dry.

Air brush is an Iwata HP-BS. Using about 25 psi.

Any suggestions folks ? Is there a thread on this already?

Edited January 28, 2010 by John B (Sc)

[Mike]

There are a lot of threads about John, but I'd try dropping your pressure a bit to around 15psi, add a drop of flow-aid (W&N do one) to your paint, and mist on the first pass. You may also be over-diluting the paint, as you've not given an indication of your proportions - the old semi-skimmed milk consistency still holds good for most paints though.

I don't tend to spray acrylics onto unprimed surfaces though, but that's my personal choice

[denstore]

How do you mean that it blobs? You spray on a surface, and suddenly a blob of paint comes?

[NickParker]

try using there dedicated thinner it contains a flow enhancer/retarder and seams to work well with model colour.Also as mike says thin it well. As for the blobs do you mean spitting?

Edited January 28, 2010 by Fisk

[baldrick]

Hi. I have used Acrylic paint thinned with cheap windscreen washer fluid for a number of years without problem.

I always give the model many very thin dust coats, letting each coat to dry before respraying.

Perhaps your putting too much paint on which then pools?

Hope that helps............

Dave..

[Mike]

I suspect he means that the paint is beading up as it hits the surface... the surface tension of the paint is causing this, so flow-aid would help there - as would being less aggressive in laying down the paint. I find that misting on the paint results in a dry model much quicker too, so patience is a virtue that pays off with a nice dry surface that can be handled almost immediately.

[baldrick]

I suspect he means that the paint is beading up as it hits the surface... the surface tension of the paint is causing this, so flow-aid would help there - as would being less aggressive in laying down the paint. I find that misting on the paint results in a dry model much quicker too, so patience is a virtue that pays off with a nice dry surface that can be handled almost immediately.

Thats what I meant!!!

[NickParker]

Actually i think I know what you mean about blobs,if you mean beading like water on a hard surface then its possibly over thinned

Edited January 28, 2010 by Fisk

[denstore]

Thats what I meant!!!

Like orange peel? In my experience, thats from the paint start drying before it hits the surface. Like Mike says, crank down the pressure and thin a bit less.

Or like water drops on a waxed surface? Again, less thinner, since the binder might not keep the paint together.

Lots of people have problem with overthinning even if the don´t know it. More thinner doesn´t always make the paint dry slower. Rather the opposite, since the thinner usually evaporate faster than the paint.

Another thing to think about, and not only when spraying acrylics, is that paint can´t be thinned more than to a certain level, and still binding the pigment. The pigment will just be like dust on the model.

Edited January 28, 2010 by denstore

[gcn]

From my own experience I don't think model color is the easiest paint in the world to AB, model air is much easier.

I assumed you have primed the surface first. Try Halfords primer on some scrap as this gives a grainy finish and see if it still beads.

Drop the IPA and just try water (distilled) and see what happens

drop the pressure, try Vallejo's own thinner, spray thinner costs moving the brush about more quickly.

or get some Tamiya and use up the spare Cellulose thinner you have left over.

[AdriaN (MLT)]

I think i know what he means by blobs. Beading- like what happens to me when i spray Klear!

[John B (Sc)]

Thanks folks, some very good advice. (Sorry for delay in returning - was doing a little flying for real (whee))

By blobbing, yes I do mean that once the spray lands it tends to blob up - not drying out, though I have had that problem with poster paint. I have primed with matt white (Allcote rtaher then Halford's - similar stuff.)

I have also washed the surfaces lightly with soapy water in case of grease build up following delays after priming.

The possibility of having over-thinned is also likely, Shall try a slightly thicker mix and reduce pressure further. Better whiff coating - indeed I may be overdoing the first sessions, too aggressive as Mike said. Hah - I should know that, standard cellulose habit. All part of the practice I need.

The flow aid and windscreen fluid comments intrigue me. I used IPA to change the surface tension - surface contact angle or wetting. Shall try your suggestion too at some point.

Interesting comment about Model Color too - I shall try some other paint makes, see if that helps. Shal investigate acrylics thinners. I've tended to assume I can use water plus surface tension agent. Maybe not !

Cheers,

John B

[T-Tango]

Hi John, if you try Vallejo Model Air paints they can be sprayed straight from the bottle as they come pre-thinned. HTH