Spray painting questions/advice

[Old Colts in Oz]

Hi guys,

Over the past year or so I’ve attempted a few small projects in order to hopefully get better at panel beating. Through trial and error I’ve been trying to learn from my mistakes. Today I sprayed the roof of one of my small cars in Primer for the second time and still had a few issues so I was hoping for some advice as to where I’m going wrong. Here is the set up I used today :

Fairly old belt driven compressor with a 50 litre tank
Short line from compressor to a regulator/water trap set at around 30psi
10 metres of hose from the regulator/trap to the gun

Previously I was using a 20 litre GMC compressor and I thought some of the trouble I was having was the compressor running out of air so I bought the 50 litre off a mate. It seemed to work really well today – instead of running flat out while spraying the roof it switched itself off about 4 times so it definitely wasn’t having trouble keeping enough pressure coming.

I have 2 different guns and I had trouble with both but for different reasons :

- Cheap gravity fed gun I bought off Ebay. The gun produces a nice flow of paint/primer however the adjustment controls seem to do bugger all. I can’t get a nice “fan” happening so essentially it’s like painting with a jet of paint instead of a fan. I gave up on this one pretty quick and swapped guns.
- Brand new Trade Air non gravity fed gun I bought from Bunnings. The adjustment controls seem to work well and I can get a nice fan when testing it while the gun is vertical. As soon as I start spraying though, the gun starts “pulsing” and paint comes out intermittedly. Sometimes it would just have air for a few seconds then primer would come through and stop again. I kept the pot at least ¾ full to make sure it wasn’t sucking air but that didn’t seem to help.

So in summary in the past I had issues with moisture and I doubted the air capability so I’ve fixed those as far as I can tell. Through the process of elimination I reckon if I can figure out the gun issues, the next job should go through smoother. A couple of things I was hoping for clarification on :

- Should I purchase a decent gravity fed gun and will this fix the problem? I’m keen to do this if the problem goes away.
- Am I spraying at the correct pressure?
- Could it be anything to do with the cleaning of the guns? My mate used to paint kitchens and he used to say the slightest bit of old paint could make your gun work really bad.
- Any other suggestions?

Apologies for the long post. Any help would be greatly appreciated.

[Tom_1569]

Quality gun will make a difference, and for painting cars a Gravity fed is a MUST.
It will depend on the gun itself, but we generally spray around 40-45 PSI for painting cars.
Yes it could possible be old stuff in the guns, maybe a new gun will fix this, and after use always run atleast half a pot of thinners through it to clean it out. Dont let the paint dry inside.
A syphon fed gun really doesnt like any angles, I also think they require much more air pressure from memory, i havent used mine in ages.
Are you thinning the primer down correctly. Anything up to and no more then 1 to 1. Always have a bit more primer then thinners, but remember paint is a completly different ratio.

[Old Colts in Oz]

Thanks for the info! Sounds like I had the pressure a little low. Because it's a bit cold here the paint shop guy recommended I thin the primer down 10% so I used 100ml of thinner with 1 litre of primer. As mentioned I'll re-evaluate with the paint. I'm tossing up between acrylic because I've used it before and can rub back my mistakes or quick dry enamel. It's just for the roof and pillars at this stage.

Tonight I pulled both guns apart and gave them a good clean, then sprayed a heap of thinners through them. It may be too little too late but they seemed to flow better with just thinners going through them. I am thinking a new gun is a good investment though. Do you reckon I could get a decent one for under $150?

Thanks again for your help.

[deanos70]

Ive just been doing something similair to you for the first time

ive have come to the conclusion that 2 guns are great to have, 1 for spraying primer, filler or putty, for spraying primer filler use at least a gun with a minimum 2mm nozzle if not maybe 2.2 or 2.5 mm,

and for acrylic use another gun with a 2mm nozzle, that way your not gumming up your good gun with heavier, thicker primer filler, i learnt the hard way trying to spray primer filler out of a 1.5 gun

i have been using suction guns, but will be getting myself a gravity fed one, not sure of the brand yet, before you spray make sure you wipe the surface down with wax and grease remover

[Tom_1569]

Tools, Spanners, Clearance, Bargain, quality, Sockets, Powertools | Transquip Direct

Thats my gun, I got it and a syphon fed for 99 bux through transquip.
Its very easy to use, and sprays great. This was our first attempt of spraying a car and we used this gun and found it very easy and we got a very good finish apart from OUR mistakes not the guns. Useing a 2mm nozzle.
If you plan on doing alot of painting I would get a decent gun but that would blow your budget quickly. But just for a hobby painter and the occasional car I would recommend the one I link you to. Have a look on transquip website you still might be able to get the 2 guns for 99bux.

It would depnd on the primer, but primer can be thinned upto 1:1 but no more, just thin it down until you think its good to go through the gun.

[Old Colts in Oz]

That gun looks the goods! I just sussed out the site and the $99 special is still on. A good price and confirmation from someone who has one and I'm sold! Going to find my credit card now.....

I also like the idea of one gun for primer and one for paint!

[R0d]

if you reckon that gun flows great get a sata jet 3000 lol, its like anything man you pay for quality, these guns are good for inside edges and bumpers. Primer guns dont need to be high quality but one that still sprays good is better. My primer gun was 115 but i cant remember the name, has 1.4,1.8 and 2.5, i use 1.8 for primer. I got my sata jet for 800 but i doubt youd wanna spend that much

[Tom_1569]

That gun looks the goods! I just sussed out the site and the $99 special is still on. A good price and confirmation from someone who has one and I'm sold! Going to find my credit card now.....

I also like the idea of one gun for primer and one for paint!

We found it a good gun at a practicle price for how much we will use it.
A primer gun is a good idea, but it means buying 2 guns, If your going to buy two guns you may aswell get one better gun with a few different tips and just clean it out properly everytime which is what you should be doing anyway.

Transquip were pretty good, I done bank deposity on a tuesday and the gun arrived thursday, I thought that was pretty good considering payment wouldnt of gone through to wednesday.

[SilverVH]

Pulsing is caused by lack of air pressure, if your gun is hammered it will either work or it won't, not sometimes it will sometimes it won't.

Crank up the air compressor and run it un-regulated at full pelt, it should stop the pulsating problem.

You might want a finer nozzle than a 2.0mm if you are spraying anything apart from primer and want a good finish. I use a 1.8mm nozzle only due to in-experience and it is a little bit more forgiving than going a finer nozzle with a pro.

I also use/used a suction fed spray gun without a drama, it comes down to an individual choice I believe.

[Tom_1569]

Pulsing is caused by lack of air pressure, if your gun is hammered it will either work or it won't, not sometimes it will sometimes it won't.

Crank up the air compressor and run it un-regulated at full pelt, it should stop the pulsating problem.

You might want a finer nozzle than a 2.0mm if you are spraying anything apart from primer and want a good finish. I use a 1.8mm nozzle only due to in-experience and it is a little bit more forgiving than going a finer nozzle with a pro.

I also use/used a suction fed spray gun without a drama, it comes down to an individual choice I believe.

DO NOT spray unregulated, EVER. One you will waste a heap of air, BUT you dont want paint shooting out at 200 psi, unless your painting the car from across a footy field. I dont know wat type of compressor your useing but Id imagine it would be capable of 120 psi, and after 10 seconds its pressure would have dropped to about 80. With unregulated air the pressure and flow will be changing constantly. Regulate the air, to 40-45 to start with, and increase if need to but dont go above 60 psi. I found old tarps great for getting the pressure and fan right on the gun. once again DO NOT USE IT UNREGULATED.

[Old Colts in Oz]

Interesting points above. The compressor I've got now is capable of 120psi but I remember borrowing it about a year ago and used it without a regulator ( it didn't have one on it ). I thought this was strange but didn't know too much at the time. If I had to guess I think the gun was only capable for about 45psi so maybe it restricted the air flow? Not sure but somehow the job seemed to go ok although maybe that contributed to the downfall of that gun! When I bought the same compressor the other week I knew it wasn't regulated so I went and bought one on purpose . The reason I bought it was that I thought the pulsing issues were air related - I was using a cheap GMC compressor at the time so wanted something bigger. Unfortunately the problem continued with the bigger compressor so that's why my focus has turned to the gun.Hopefully my new gun comes this week and I will try the painting on Saturday. I'm going to test the gun with thinners, then start spraying at around 40psi and turn it up if need. Will update the thread with how I go .

[SilverVH]

Where did I say to spray the car un-regulated....wholey **** there are some morons here! If you read I said to check for the pulsating problem geezus lol.

Just off the record you can actually spray primer un-regulated and a lot of people do, so I don't see where you are pulling your information from regarding un-regulated air supply...

[Tom_1569]

Crank up the air compressor and run it un-regulated at full pelt, it should stop the pulsating problem.

Where did I say to spray the car un-regulated....wholey **** there are some morons here! If you read I said to check for the pulsating problem geezus lol.

Just off the record you can actually spray primer un-regulated and a lot of people do, so I don't see where you are pulling your information from regarding un-regulated air supply...

LMAO, Are you serious???? Im a moron for CORRECTING something you CLEARLY stated.

I dont know if you have ever sprayed before, but an air compressor will NOT hold one PSI, it will loose pressure before the motor kicks in. It will NEVER have an ever flow of air if it is UNREGULATED, yes it is possible to spray unregulated, but it makes things more difficult and you will never get an ever coat.

Sorry about the Dementia

[Old Colts in Oz]

So the new gun arrived on Thursday and the sun was temporarily shining Friday afternoon so I thought I'd test it out. I ran some thinners through the gun first and it all seemed good. Masked up the car's roof, mixed the paint, and had a go. ALL GOOD! I can't beleive I've managed to spray a couple of things in the past with my old set up. The gun was very responsive and the compressor had no trouble at all keeping up pressure ( only switched on 3 times ). My moisture trap/regulator that I bought the other week worked a treat and it maintained the pressure at about 40-45psi. Once done, I ran half a cup of thinners through the gun, then pulled off the cap needle etc, cleaned them in thinners, then ran another small amount of thinners through the gun again. I have 2 sheds - one where the cars are and a smaller "workshop" where the bench and supplies are. I thought it was crap having bought a bunnings spec compressor first so now I have 2. Turns out that isn't so bad. Instead of having to move the big comp to the small shed so I could clean the gun with air, I fired up my little comp for the task - worked sweet! I also went down the local salvage yard during the week and bought an old stainless steel laundry basin/cupboard as somewhere to clean up. I ran some pvc pipe from the sink drain into a big bucket. That worked really well too! I was able to place all the stuff I needed cleaning in there and point the spray gun into it while running thinners through the gun - it was cleaning the gun and the various mixers, pots etc at the same time! All up I'm really happy and can't wait for the next project to work on technique now that the set up is good. Thanks for everyone's advice

[SilverVH]

Bro, theres a difference between cranking up the compressor un-regulated to see if there is a pulsating problem compared to cranking up the compressor to completely spray a car...maybe I should have made it a bit more clear, I was referring to running it un-regulated to see if the pulsating problem stopped, therefore eliminating a possible cause of pulsating, I didn't mean for it to refer to spraying a car un-regulated...

For the record yes I have sprayed before (6 years I've been around it) I guess I should've gone more into depth instead of assuming people would use common-sense lol.

Sounds like your getting the hang of it Old Colts, its amazing the difference a new gun makes, even if its a ****ter, just be wary with cheaper guns as they wear out quicker. What mm nozzle are you spraying with and what type of paint did you use? Once you get the hang of things you can use a finer nozzle and the finish will be amazing. It really all comes down to technique/practice.

Make sure you have fun at the same time also!

[Old Colts in Oz]

Because I'm still a novice I went with acrylic and the gun has a 2mm nozzle. I've used Acrylic once before and I like the "rub back and fix mistakes" concept. I think as I get more confident I'll try 2 pac/Enamel and try out a 1.8mm nozzle

[Tom_1569]

Because I'm still a novice I went with acrylic and the gun has a 2mm nozzle. I've used Acrylic once before and I like the "rub back and fix mistakes" concept. I think as I get more confident I'll try 2 pac/Enamel and try out a 1.8mm nozzle

You bought the same gun as me yeah? If you did different size nozzles are available. Ask transquip they should sell you some, im going to email them soon and get a few different sizes.

Was the regular/water seperator one off ebay? I have one of them on their way to be used on my new compressor. I did buy one of their seperator/oil/reg for air tools but unfortunatly it leaks no matter how much thread tape is on it im hopeing the water seperator is a bit better.

best of luck with your spraying, post up some pics to.

[Old Colts in Oz]

Yeah, same gun from Transquip -they were really good. I will contact them regarding getting different size nozzles. Can you guys shed some light on that subject for me? I've heard that a smaller ( 1.8 ) gives a better finish but not really sure why. Would it be fair to say that with different size nozzles for the same gun you could use primer and paint with the same gun but with different results ie. use a 2mm for primer than 1.8 for the paint?

I looked at those Ebay water trap regulators and bid on a couple for around $25 plus postage. Got outbid as I wasn't sure what they were worth so didn't keep bidding. Then I went into Supercheap and they had them on special for $24.95 so I bought one. It works realy well. Before buying that I was just using a "last chance" trap on the gun ( see photo below ). This thing cost about $12 from bunnings. With the last job I used both the trap/regulator and the last chance one as I figured it couldn't hurt.

Here's a couple of pics of the project. I picked up this 67 Colt 1000 Sedan really cheap as it was on it's way to the wreckers. It's got a fair bit of rust but the main thing that needed attention was the roof. I haven't been able to find the original paint codes so a quick fix was decided on to paint the roof white for now. Because the rust was so bad I had to wire wheel it back to metal. In hindsight I wish I'd spent more time fixing the dents etc but my objective was to clean up the rust so I guess that was achieved.

Bare metal where the rust was:


In primer :


The gun set up with moisture trap attached :


Supercheap regulator/trap. I have cheap hose from tank to trap, then my good hose runs from tap to gun :



Quick photo after spraying :