Spraying Metalic Solvent Paint Help Please

The paint tip seems very small I use a 1.2mm or 1.4mm in a standard gun and 1.1mm in a small touch up non gravity feed gun, is your atomisation correct? if it's too fine you will get spray dust bouncing around and in the air. You may also be getting too much dust because the fine atomisation is drying the paint in the air almost instantly it comes out of the gun. You could describe it as not being "wet" enough.

Is it an HVLP type gun as most are, you could try increasing the tip retraction to produce more fluid which might help reduce the dust as the paint would be heavier.

How are you mixing the paint, simply in a cup, by a viscosity cup with a timer or by a measuring stick? all will produce different results unless you are using the correct process as suggested by the technical sheet.

You could try finishing with a heavy wet coat and if it is two pack check what hardener is correct for the temperature, I use very fast drying hardener normally but on a warm day then I revert to straight fast drying hardener.

Hope this helps.

 

Spraying as you know\have found out is very subjective. What works for some won't work for others because of many factors including technique, temperature, type of paint and the list goes on.

If you are using a 1.3mm syphon gun then that should be big enough as the 1.1mm gun I use can spray quite large areas for its size. It's supposed to be used for door jams and other small areas and I use it for painting numberboards, so if you are spraying casings with it then it should be up to the job.

You pressure seems high, I use about 50 psi constant at the gun but you should go with the manufacturers recommendation and if that is too low then up it about 5 psi and see if it improves. Don't set the gun to 60psi and then use it because it will operate at a much lower pressure, I assume you know this?

A 2.5hp compressor is a little small but it depends on what it is. I use a 3hp twin cylinder two stage compressor with a 50 litre tank and that is good enough using a 1.8mm tipped syphon gun to spray a car. If your's is just a 2.5hp single cylinder single stage then it might be on the small side. Are you get a big pressure drop or is your pressure switch set too low on the tank pressure side. It shouldn't be but I have found my 2hp compressor which is single cylinder and single stage is firstly not good enough to try and spray anything decent with it and also the pressure fluctuation is a little too great, this is down to a sliding pressure drop at the gun, a common problem, you might start of at say 60psi which gives a good pattern only to see pressure drop or fluctuation that stops the gun performing as it should. This would then also be a free air delivery problem. My little compressor is fine for blowing up tyres and small air tools etc. but not good enough to provide a decent spray job.

It sounds like you are using metallic cellulose or a non two pack acrylic type paint, I assume it's not water based which is very different to spray.

It's obviously not two or three pack, which is fine and in which case have you tried using more thinners to wet out the paint more. I use two pack for Ducati colours and it also requires a ratio of 10% thinners but I always go for more and range it up to about 20% to 25%.

If you are using quick flashing paint in this weather, like yesterday (very warm) then your paint is going to flash so quickly it's not going to settle.

If you have what I term a bird seed finish you need the paint to be wetter and not too quick to flash, it needs to flow but not be so wet as to dry slowly enough to run.

On the face of it you are being very meticulous but probably just not picking up on one small element.

I have been spraying, not professionally, for many years and I know how difficult it can be to get the right finish and the time it takes to get things totally spot on.

I hope the above general advice helps and maybe even try spraying somewhere more open that can allow overspray to blow away without swirling onto your work.

Professional setups use downdraft booths to get rid of spray and fumes but very few have access to those sort of setups.

 

You need to trigger the gun and have it roughly adjusted for the amount of air you want to pass through it or set it a bit higher.

With the trigger depressed set the pressure and that way you will get constant pressure for as long as the compressor will deliver it, this should be constant and not drop say below the 40 psi you quote, if it does then the compressor cannot keep up with the gun so your spraying will be affected.

Here's an example that I am actually using today, if this helps. I am using an air gun to clean out some bike bits. I want to spray air to clean things at 60psi, I trigger the gun and adjust my 2hp compressor to deliver a constant 60 psi, so I adjust the air flow with the trigger depressed and set it to 60psi when I shut the trigger off the pressure rises and settles at 77psi but as soon as I trigger the gun it will go back to running at 60psi. It will run at 60psi putting out air without dropping until the pressure switch kicks in, when that happens it will put out 60psi under free air delivery until I stop using the gun. The pressure will then climb to the maximum of 77psi and If I use it in between it will go back to putting out 60psi.

This is how your gun needs to work all the time so that everything you spray is always sprayed at the correct pressure and without fluctuation. A compressor that cannot do that is no good for spraying. I would say you should be fine on the compressor front as it should be easily able to cope with the needs of the gun.

You can get a gun inline pressure adjuster which can help, I have one but do not use it, they are cheap and useful to have as it can stabilise small fluctuations and allow fine adjustment, Machine Mart do them.

If you need anything else then let me know. If you get this right you will at least have one less variable to worry about.

 

Now it is purely there to make fine adjustments at the hilt of the gun. Mine works on an oval principal in terms of passing or allowing air through. It is really for that final adjustment to the last few pounds of delivered gun pressure.

A water trap is an entity unto itself but is often combined with larger regulators or wall hung inline regulators\oilers. It is important as water can be trapped long after a decent spray job has been completed, if it happens you then get micro blistering in very cold or adverse weather. The spray (air delivery) needs to be as devoid of water as possible in order to allow for good settling of the paint.

An important art to learn is that of rectification on deficient jobs, which could just be flatting off or more severe rubbing down or the elimination of runs or sags. It just takes time and practice and even professionals turn out some pretty poor jobs at times, even though there is no excuse.

See the link below here is a decent one from Amazon at just over £5, it might help if you feel you might need it. This is not the oval kind but a straightforward reducing\enlarging fine airflow regulator. As you can see this once was nearly £20 so it's not a bad buy and is probably better than my one and easier to use as it is a simple governor. You can adjust pressure on the go with one of these without having to balance at the compressor\regulator, just point, open the trigger and adjust.

Mini Air Regulator for HVLP Spray Compressor Gun & Air Brush 1/4" BSP: Amazon.co.uk: Car & Motorbike

 

Makes for interesting reading - thanks guys!
I'm a year in to an airbrushing hobby and although I'm concentrating more on fine-detail art/portraits, I would one day like to custom paint bikes and helmets.
I've dabbled with a spare crash helmet, and bought a motorcycle panel to practice with, and got relatively okay results. I use water based paints & solvent based for detail, then use a 2k lacquer to finish with.
There is so much information to learn that I'm going to work on getting the most out of an airbrush first, then when that becomes second nature will look into adapting that into auto custom paint work.

 

I am glad that has helped you, you will find you can now find out exactly what your highest pressure will be on free air delivery that any item such as sprayguns and tools will deliver. Big tools use lots of air and some may be beyond the capability of your compressor so it's always good to know it's capabilities before you buy a new gun or tool.

You have now eliminated one potential problem that could have contributed to your refinishing problems, the rest will be down to other factors.

I am glad you found it interesting, I have done a lot of custom work in the past myself and airbrushing is a real art to master. There are some good books on technique out there. I used to use the Cal Custom range of paints which have now been taken over by House Of Kolor and a few others. It really is a case of practice makes perfect and airbrushing is popular in many areas even beyond auto work. I have 10 sprayguns for all my work 3 of which are airbrushes my best one being an old Badger 3000 model If I remember correctly which is a double action model. It's quite hard to master I found, good luck with your endeavours.

 

Thanks Red

I'm a member of a good online airbrushing forum which has a section aimed purely for beginners techniques. I'm currently trying to master hair, which is an art in itself!
I am yet to try Kustom Kolors but like Inspire paints (solvent) and Auto-Air (water).
I have quite a few airbrushes and 2 spray guns - one is gravity with a 0.8mm setup, the other is siphon with a 1.4mm setup. They're both cheap and cheerful and good to learn with, but if I ever get round to serious work I'll invest in some quality guns.
Thanks again - it's very helpful hearing advice from pro's!

 

Forums are very useful I agree, as you will already know there is a wealth of knowledge just on this one alone and of course they can often provide links to others things.

I remember when airbrushing on cars and vans was a very big custom thing and below is a link to one of the late 70's\80's great airbrush artists. He did a number of famous show cars including a Rolls Royce in sepia tones.

The other link which might be on interest is from Mike Fairholme who paints crash helmets for many well known racers of cars\bikes\karts etc. I first met him when he painted my own crash helmet when I used to race TZ Yamaha's a while back. You might find their work interesting and possibly inspirational.

Good luck, you have some good equipment already and certainly good enough to start off with.


Welcome to Fairholme Designs - Enjoy Your Stay

Ray Mumford

 

Thanks Red.

I'm currently at work but will take a look later on.
There's a guy on YouTube who paints guitars is hugely inspiring to me. His name is Svee Wheeler and what he can't do with an airbrush isn't worth knowing! If you get a chance then I recommend you look him up - anyone with even a slight interest in airbrushing would be amazed at what he does.

Anyway, sorry Noods for hijacking your thread.

 

Depends on what temperature you were spraying at, yesterday was very warm and certainly too warm to spray unless using a slow drying hardener.

If you have lots of dust swirling when you spray then it will settle on the surface and it depends on when it does, it will either blend in, or if it's settles when paint has flashed more then you will get dust on the surface. Are you surrounded by any fine dust?

Spraying anything outside a proper professional booth will always cause a bit of dust to drop in from the atmosphere it just depends on how bad it is.

You can always rectify it by finishing your sprayed surface with 1000 or 1200 wet and dry and rub it down wet and then finish with one wet coat of lacquer.

What many don't realise is that a good finish is actually down to the final rubbing out when it has fully dried. The hard part is you are spraying matt lacquer so you need to fully rub it out and finish with one decent coat keeping as much dust\dirt out as you can. If it was normal lacquer you could no doubt just rub it out and then compound it.

Wet sanding is a real art and any top professional will spend a long time wet sanding a finished item and then compound it to finish.

If you need anything else let me know.

 

A wet coat is a double\triple even quadruple heavy coat that lays on the panel (or whatever) so that the whole panel is completely shiny, and sorry for saying this, looks "wet", it will be really glossy and actually look like you want it to finish up looking like, except that as it flashes it will retard back somewhat.

A wet coat will take slightly longer to flash off, and there is of course the danger of a run, but you will see a more even finish that will also tend to settle out flatter. It's hard to describe in words but you can see it and know it's right when you are spraying. It also absorbs any slight tendency for fish eyeing of siliconing or any other very small "nasty" that might find it's way onto the panel (insects!!). I am sure you will have experienced these already as it's something that happens from time to time with everyone (there is an additive that reduces siliconing)

If you are nervous initially about applying too much lacquer to finish off just spray a double coat in quick succession allowing less flash off time (or even none) and see if that gets you nearer the mark.

Let me know if you need anything more.