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Spray painting - The spray gun.

Which spray gun to choose?.




Spray guns.


Now we know which compressor is suitable for your needs it's time to focus on which spray gun you may need. First some words in general about spray guns. Well, "some" words are an understatement but you know me, I'll write everything down I know about an item. Just for you, so you can make a decision on what you need and what not. And yes, I will tell you what I use and why.

There are very many spray guns on the market, let's divide them in groups so it's easier to find out which one suits your needs.
Suction spray guns.

This is the grandad of all spray guns, it has got a container under it in which you put the paint. By means of the air pressure the paint is sucked up and directed to the nozzle. The nozzle will nebulize the paint, that way you get a nice "mist" which you can regulate. I'll be talking about the controls later because it's the same for most spray guns.

Sprayguns



Normally they come with a needle which is in between 1.8 and 2.5 millimetre and yes, you can still buy them. More about the size of the needles later on. As you expected that goes for every spray gun. They are not extremely expensive and a spray gun like this is nice to have. It's very good in spraying paint you don't want in your spray gun for basecoat and clearcoat, for products like POR15 or undercoat it's marvelous! Be aware, using it pointed up (for like the underside of the car) it has got it's issues.



Sprayguns



You can see from the picture the suction pipe is pointed forward, tilting the gun backwards will leave you with only air coming out. The paint will be in the part of the cup that's away from the pipe. Never tried it but being it one of the dinosaures it may be possible to point that pipe backwards, in that case you'll have an awesome spray gun to use pointed upwards.

Normally this kind of spray gun is not suitable to paint your car, meaning re-doing the paint and the finish. Whether it's basecoat or clearcoat you just don't want this one. I do know there are people who still use it putting primer on and even the finishing coats. Well, that's an art in itself! If you read this chapter and are one of those people who still do, I have the greatest respect for you! Be sure it isn't easy!


Gravity spray guns.

Nowadays the most commonly used spray gun. Having said that, they have been around for like 3, or even 4 decennia! The big difference is the cup which holds the paint is not underneath but on top of the spray gun. Gravity will let the paint flow into the nozzle so there doesn't have to be any suction. Here's a picture of one.

Sprayguns



It may come as no surprise there are very many brands out there, ranging in prize from less than $ 20.- / 15.- GBP up to well over a thousand dollars. There is a gravity fed spray gun for every budget. The question arises whether an "el cheapo" spray gun does the job and at the same moment, will $ 1000.- or more for a spray gun really gives you that much more? And more of what exactly?

Build quality is one thing you should be aware of, I'm not saying the $ 20.- spray gun won't work but it may have it's issues like leaking or dripping. In general there are no options available so you'll have to do with what you get. Even in the cheap section of the market you may be able to find a spray gun with an 1.8 mill. nozzle and one which is equipped with an 1.2 to 1.4 mill. nozzle and needle. The first is used for primers, the second one you can use for base coat and clear coat.

The more expensive sprayguns, let's say starting at $ 150.- up to $ 300.-, have a whole range of things you can change in and on it. Aircaps, nozzles and needles are the most important, on top of that you can rely on every single part to be available as spare part. In contrast to a cheap spray gun, if something breaks or needs to be replaced you'll be lookin at a new spray gun. In the long run it can even be more economical to buy a more expensive one. Another advantage is you can change the needles and the corresponding nozzles in them, so now you need just one spraygun for any kind of car paint you want to spray with it. Just change the needle and the nozzle.
Yet there are some sprayable things you don't want in a spray gun which is dedicated to spray paint a car. A few of those are latex paint, POR15 and various sorts of undercoating, the bitume stuff as well as Waxoil. Those products have a habit of gumming up your spray gun which makes it unusable for car paint. Waxoil is even worse, it makes your spray gun unusable for car paint right away! Use the tools Waxoil sells to put the stuff on!
However, you will be able to use solvent based paints and water based paints without any problem using the same spray gun.

Be sure, in general the more expensive spray guns will provide you with a far better "fan" as it's called. That is the spray pattern which is coming from the nozzle and yes, it does have a great impact on the results.

Then the really expensive spray guns, should you have one? I'm not sure because I never spent more than 300 bucks on a spray gun including different needles and nozzles. In my opinion those are for professionals who use it every day and who are able to tell the difference. Of course, if a really expensive spray gun makes your work easier and you're looking at 3 cars a day to be painted, I guess it's worth it.


Other spray guns.

There are two more kinds of spray guns, the touch-up spray gun and the paintbrush spray gun. Since I don't do paintbrushing I'm not going to talk about those guns.

The touch-up spray gun is actually a smaller gravity spray gun. They most likely come with needles and nozzles which are 1.0 and 0.8 mill. The cup that holds the paint is smaller as well, you're supposed to repair small area's with those. Of course you can buy touch-up guns in various prize ranges like it's big brother and actually the same story as above goes.


Needles and nozzles

I'll give you a general guideline which needle with corresponding nozzle to use with which kind of paint. I'll be focussing on spraying cars and parts.

Needle size

Used with:

0.8 - 1.0 mm

Solvent and water based base coat, solvent based clear coat.

1.2 - 1.3 mm

Solvent based base coat and clear coat.

1.4 mm

Water based base coat.

1.8 - 2.0 mm

2K Primer / filler. 1K Etch primer, epoxy primer and isolator paints.


HVLP

In the previous chapter about compressors I mentioned HVLP spray guns. Let's begin with the abbreviation, it means: High Volume Low Pressure.

This is a trent that's been going on for a while now but what are the advantages? Are there any? Well, yes! Getting more paint out of your spray gun at a lower pressure will reduce the air demand from a compressor. Hence, a smaller compressor can be used or at least one which doesn't have to build up the pressure sky high. Like many things in life, it's eighter the one or the other. In most cases an HVLP spray gun helps to economize the air needed from your compressor. On the other hand relying on a smaller (or less powerful) compressor may limit the use of other air-tools you want to use. Be sure you will be using other air-tools once you got a nice compressor.

HVLP spray guns typically run very well on like 2 bar / 29 PSI or even less. Rule of thumb: the thicker the paint you want to spray the bigger the needle and nozzle, at the same time: the thicker the paint the lower the pressure. You can spray primer at like 1.6 bar / 20 PSI, base coat at 1.8bar or 24 PSI and be sure you open up the gates to 2 bar / 29 PSI for clear coat.

Normal spray guns will need up to somewhat more than 4 bar / 58 PSI to operate properly. The practical side of any HVLP gun is it won't drain the air stored in the tank of your compressor in no time. You'll still need a good size compressor though.


Last update : September 7th, 2018