Compressor Pressure And thinning acrylics

[ChrisS]

Guys,

 

What's a good compressor pressure rule for both detail and cover work, and does it relate to thinning %?

 

I'm about to start camo on this ex-LW bird and I'd like to know what you guys do. I'm using Polyscale acrylics thinned with Isopropyl.

 

TIA~

 

Chris

[maverick728470]

Chris,

For any water base paint,it's usually about a 3-1 ration or 4-1.That three parts paint and one part water.Test it by shooting it on a piece of paper.As long as u get a goos coverage,u got it.And for compreesor PSI.Somewhere between 25-30 psi,That's pounds per square inch.Water base paints tend to run when sprayed some.But again,test u'er minxture to see how it covers the paper or a piece of plastic.Larry

[Tony O]

Chris,

the viscosity of the paint is just one aspect.

 

I wonder if anyone has ever tried to contact the paint makers to ask this one?

 

It depends on the airbrush tip as to what you can get away with as regards pigment and viscosity and pressure.

ideally spraying at low pressure will give the best results as the paint will hit the surface at a relatively slow speed.

However the paint will need to be drastically thinned to allow it to pass through the airbrush tip at low pressure, which starts to bring up problems of opacity. (they also go off quicker when drastically thinned, leading to brush clogging problems)

The main problem with acrylics is the chemical/air drying process is also accelerated by temperature, so there is really no hard and fast equation to put down. I've never tried using a retarder with hobby acrylics, but have used it with my tube paints (Cryla) and in an airbrush (Iwata HP-A)

IMO

It is really a matter of starting off with a milky mixture and spraying at say 25psi and I usually spray at about 4 to 5 inches from the surface.

To spray closer the pressure has to come down and the paint thinned more, Also try adding a crown tip to your brush if you don't already have one. These allow greater atomisation of the pigment as it leaves the tip and prevent spatter and paint buildup on the tip.

Also worth remembering is that a higher pressure and thicker paint will result in a much 'grainier' surface as the pigment hits the plasitc and 'bounces' off. ( I'd add to Larry's post that paper tends to absorb the water/isothinner and leave the pigment on the surface), I use a sheet of styrene and when it gets covered in paint, I spray over with auto acrylic white primer. I Keep it near or beside the kit in progress and test before hitting the kit plastic. Spraying at low pressure means that there should be little or no overspray from the test sheet.

There was an article a few years ago in FSM which did a bench test on a few brands of acrylic and the optimum pressure/thinning ratio from which to start.

As with all painting, its not the painting its the prep work you put in that pays dividends.

I can dig this out and scan it for you if it might be useful.

HTH