Newbie's problems when airbrushing

[Guest]

Hi guys,

I am having problems when airbrushing as the finish turns out to be like a sandpaper texture. I am using dual action airbrush revell white paint thinned with revell thinner 1:1 ratio. I have sanded the model with 600 grit sandpaper and washed it in a soapy water. Then applied revell white primer (probably a mistake to buy white primer when paint will be white as well). Had problems seeing what is covered. I have tried 10-20 psi and different distances from the model. I have tried to spray humbrol in matt colour on some pieces and it looked quite fine with matt finish but still smooth whereas I have also tried revell matt colour which turned out to have sandpaper's texture. I would really appreciate if someone could tell me what I doing wrong? And if you sprayed revell enamel please share your settings. Thank you.

[Guest]

Sounds to me like the paint is alost dry before it hits the model. I assume the revell is Acrylic? If so that might explain whey the humbrol (if enamel) is smoother as the acrylic dries very fast compared to emalel.

why not try a higher pressure to atomize the paint better, also hold the AB tip closer to the model if you can. Sometims you will get the texture you say in areas where there are sharp corners but little can be done about this.

Theuns

[Guest]

Both Humbrol and Revell that I am using are enamels. What should be a good starting distance? At the moment I am spraying around 10cm from the model. Regarding the pressure shouldn't it be lowered when moving closer to avoid paint runs? And do you usually sand down the primer as well since I didn't which gave the sandpaprer finish from the beginning. What is preferred pressure for enamels in general? And since I have ruined the paint job what is the good way to remove it without breaking a bank? Thank you.

[Guest]

First of all, for paint removal see here.
Effortless, safe and removes cellulose (lacquer) enamel and acrylic.

The problem has several possible reasons so I'll cover that in a separate reply.

[Guest]

It's unusual to get a rough texture when spraying enamels as they flash off very slowly.

Spraying white, (or any very pale colour), is harder than a dark colour or metallic as they're less opaque and you have a natural tendancy to lay the paint on too thickly, white on white is tricky as you discovered but will yield the best result, the trick is to spray it with a good light source so you can see the reflectiveness of the wet paint easier and see when to stop before you get runs.

So far you're doing the right thing re using the recommended thinner for the paint, so going through the whole setup from start to finish
1. make sure you're getting a clean spray and pattern from your airbrush, check by spraying some thinner through and make sure there's no sputtering or hesitation to indicate a bad seal or air leak.
2. Stir the paint thoroughly to ensure the oil base and pigment is thoroughly mixed then shake it thoroughly, this can take a while with a well settled and separated enamel paint.
3. Thin the paint separately in a pot to the consistency of milk, (this is a tricky one but the best way to see what I mean is to pour a little milk in your mixing pot and swipe it up the edges with a brush, it'll seem very thin, which it is, (the most common problem with enamels being sprayed is that they're not thinned enough), you'll note that it will leave a thin translucent coating on the edge, aim for that with your paint/thinner mix.
4. Start with a pressure of 20-25 psi and just practise on some scrap plastic / an empty plastic bottle / anything that doesn't matter to you, practise the distance and amount you pull back on the trigger to find what suits you, it's different for everyone, adjust the pressure lower if need be, (it shouldn't be necessary to increase it).
Your first coat should be a mist coat covering the entire area, don't aim for a wet coat in the first pass, you'll most likely get runs, especially with pale colours.
Your second pass, spray with a good light on the item you're spraying, and look for it to gloss and start to shine, this is where you must stop even if it's not covered the base primer yet.
If necessary repeat after a couple of minutes to let the last coat level and the solvent to flash off a little.
leave somewhere to dry for at least 24 hours before trying to handle it, (it may need a little longer)

If after following this procedure you're still getting a rough textured finish, try a different paint, I rarely use Revell enamels other than the odd pot I bought because they were there when Humbrol weren't but the ones I tried seem to behave similarly but it's possible to get bad ones of anything, I had a very old pot of Humbrol white and a clear gloss that lumps formed in from the pigment leaving unsightly lumps in the paint finish.

As a final note, you mention a rough finish on the primer, if that's not smooth, it will translate to a rough finish on the layer above, the base model and primer both need to be smooth but sprayed well, sanding shouldn't be necessary.

[Guest]

Thank you for very thorough reply. When this sandpaper finish appeared for the first time in the model I just took 600 grit sandpaper and wet sanded the whole model to make it smooth again. Then I reapplied paint again but it appeared to be rough again. Then I left it and came here to ask for advise but today when I checked the model it is far from perfect but it is decent for the first paint job. It has some orange peel effect and dust particles on it. Could I just wet sand it to remove inperfections and dust and apply another coat? Is 600 grit too harsh to do that?

As for the paint striping I bought oven/grill cleaner spray and applied on parts that I want paint to be removed and put in the plastic bag. I read it that it should help.

[stona]

I've always sprayed enamels, numerous brands, and can't think that I've had this problem. However, a couple of things do come to mind.

First, 600 grit is a very rough paper to sand a model prior to priming/painting. I would suggest at least 1500 grit, you can even go much higher than that. I polish primer with denim material as a final operation.

Increase your pressure, don't be afraid to go up to 35-40 psi. This is about the only point with which I disagree in the excellent post above. Very few modellers use higher pressures, a lot of artists do. You won't damage anything by trying

You already have advice about thinning. You will have to experiment, it is impossible to say exactly what ratios you need, they vary within paint brands and everyone's set up is different. If you are getting runs it does not necessarily mean that the paint is too thin, you may be introducing to much paint into the mixture. Operating a double action brush is as much art as science and, again, you just have to practice, get a feel for what works for you.

The advice about paint mixing is critical. Mix your paint until you are convinced that it is completely homogenised....and then do it again before using it.

Once again, as above, practice on something that doesn't matter. It is not reasonable to expect perfect results at first, but you will certainly be surprised how quickly you get the hang of it.

Good luck

Cheers

Steve

[Guest]

Thank you guys for helping me out. This keeps my spirits up. Why there are so many different opinions when adjusting pressure? I heard that optimal is 15-20psi but as you said I should go higher. How does the pressure effects how you use the airbrush? The lower the pressure the closer you could get to the model and vise versa?

[stona]

I heard that optimal is 15-20psi but as you said I should go higher. How does the pressure effects how you use the airbrush? The lower the pressure the closer you could get to the model and vise versa?

The pressure really shouldn't make any difference to where you hold the brush relative to the model. More important is controlling how much paint you introduce into the mixture.
I will give the example of the mottle found in much Luftwaffe camouflage, which seems to terrify many modellers. You will read all sorts of advice about it, thinning paint, reducing pressure etc. I spray it exactly how I spray everything else, 35-40 psi, paint thinned as usual. For mottle I may need to move the nozzle to within a few millimetres of the model, the same for making a reasonably tight demarcation between colours. For spraying larger areas the nozzle may be a a few centimetres away, but exactly the same set up works for both.
Don't overthink the problem, as many do. Once you find out what works for you everything will fall into place. Experience will make things ever easier too. I never measure proportions when thinning my paint. Over the years I have developed a feel for what is right and (amazingly even to me!) I usually get it right without measuring anything. There's no reason why you can't do the same with a bit, well, a lot, of practice.
Cheers
Steve

[Guest]

Thanks Steve. I think I finally nailed the settings at least for flat colours. 15psi and 1:1 ratio works well for me. By the way since my revell thinner ran out I bought turpentine and quite like it to use as a thinner probably due to it evaporating slower I could lay nice wet coats. On the other hand I still having problems with gloss colours (please see attached photo). What causes this orange peel effect? But as you could see top part is looking a lot better but the problem is I do not remember what I have changed in my settings or technique. Therefore if I could find out what causes the effect on the lower part I could try to improve.

https://www.dropbox.com/s/y6rj35pt58zj7co/IMG_20170807_214031.jpg?dl=0

[stona]

It's not easy to see what exactly is going on, but it may be a couple of things.
The paint might not be completely atomised in the aerosol created in or at the tip of the brush (I can't remember what you are using, but it is probably an internal mix).
The only way to cure that is to up the pressure a bit.
It also looks as if the paint maybe a little bit too thinned. Try upping the paint ratio slightly, just by 5-10% and see what happens.

You did say that you have a double action brush.

This may seem obvious, but as I have given airbrush instruction in the past I'm going to say it anyway! Don't try and control the pressure with your trigger. I'm not sating that you do, but I have often seen people try to do this by attempting to control the amount they depress the trigger. It is impossible to get any sort of accurate control as the trigger is not designed to do this.
Set the pressure at your compressor or whatever supply you use and only control the paint input with the trigger. Push the trigger down completely to start the air, then pull the trigger back to introduce the desired amount of paint to the mix. Some brushes have a means of setting this as a preset limit (on the amount the needle can be pulled back). When you reach the end of a pass you can stop the paint and air together.

I use several brands of enamel paints and only ever use what in the UK is called 'white spirits' (mineral spirits in US/Canada, sometimes turpentine substitute) as both thinner and cleaner. It's cheap and effective.

Cheers

Steve

[Guest]

Hi, it is me again. I am not sure if it is turpentine that I am using as a thinner or something else but paint does not seem to stick well. I dried for a couple of days and during handling when trying to glue to another part look what happened. https://goo.gl/photos/3x1deQCCKvV5S4bLA

[Guest]

It looks like you're trying to stick a painted piece onto a painted piece.
Styrene glue works by melting the parts slightly and bonding them to one another, it will dissolve any paint because it's a 'hot' solvent and paint to paint will often result in the paint melting and the parts separating.
Where possible, it's best to make pre asemblies of the same colour prior to painting, if that's not possible you need to carefully scrape the paint from at least part of the surfaces you're gluing and use carefully applied glue, (using a cocktail stick for example), so it doesn't spread and ruin visible paint.
Also, to clarify on my earlier post and as Steve said, the PSI figures quoted aren't set in stone, they're based on what works for me with various paints and as per Steves insights, (and he makes some cracking models) he suits a higher pressure for painting, it's about experimenting and finding what works for you and the distance you prefer to spray and the speed at which you move the airbrush. Don't expect to get it immediately, I used to spray vehicles in a workshop, precise paint mixes and optimal pressures and guns and nozzle sizes etc and it still took me a few hours practise when I first used an airbrush to adjust to how they operate.

[stona]

What he said really. I build sub assemblies as large as is reasonable before painting. This obviously depends on the model and what colours are required. If I have to attach previously painted parts I scrape the paint off the mating surfaces and am extra careful with the glue. As an aircraft modeller I can keep this to a minimum, but there is always things like undercarriage doors that need this treatment. Sometimes a touch up is still required (the area where things like antenna masts or pitots attach always gets me )
Cheers
Steve

[Guest]

Guys I was enquiring about the paint coming off after handling (steering wheel and top of the dashboard). I let it dry for more than 24 hours. I am suspecting that the turpentine that I am using as a thinner does not allow paint to dry completely? I have tried scratching the paint and it seems oily not rigid. But I thought 24 hours is more than enough for enamel to be dry.