Inexplicable bubbles in cellulose!

[PerplexedByPaint]

Argh!

Just had to get that off my chest....

I'm currently in the middle of a fairly large project, stripping all the old paint off a mercedes clk, blasting the rust off, filling and so forth. I'm now up to the colour coats (phew) and I'm using a straight forward black cellulose with a recommended 1:1 thinner/paint ratio.

All went well spraying the etch, primer, wet flatting and so forth until the colour coats. No matter what I do I always seem to get tiny little bubbles that look like overspray in the colour coats, straight out of the gun. If i sand these down, I'm left with tiny little holes. Enough sanding does eventually get rid of them, and I can then polish everything up to a decent standard, although it's taken me about two weeks to get them all out of the bonnet to the point that I'm happy to lacquer it!

I'm aware it may be contamination of my air supply, but I find that odd since the etch and primer were ok - how could I check if there was sufficient oil in the air to cause this? I've got umpteen traps on a copper pipe system with drains... If the problem were my compressor, is there anything I can do to clean it out and rule it out as the cause?

I'm at my wits' end! Can anyone shed some light on this?

 

[the snooper]

its usually water thats causes the problem how close is the water filter to the compressor

 

[BillFarworth]

Well if you have trap it shouldn't be any problem.As snoop ask you how far from you spay gun is the trap?There is a possibility the whole issue to be the hose this is the reason of the question?

 

[Chipper]

Could do some simple elimination/tests, i.e different gun and paint on same comp. If it shows problems, the comp/supply must be at fault.
If all OK, try the celly with the 2nd gun.

 

[brightspark]

i run 2 water seperators on my set up one on the compressor tank and a portable one on the air line about 4 meters away from the spraygun using a 10mm hose and a smaller one to the gun . the line is best kept straight as possible to eliminate any build up of moisture

 

[malcolm]

Do you have a coiled airline or one on a reel? That could be the source of water. Straight hose is safer for spraying.

 

[PerplexedByPaint]

Fixed!

Hi all,

Thanks for all the suggestions - sorry I didn't post back until now!

I tried a straight through air hose instead of the coiled one and it didn't make a difference, unfortunately! The last water trap in the system is probably about three yards from the gun, but not much water if any was reaching that far (drain valves and what not before then).

Turned out to be a faulty pressure regulator - being the newbie that I am I didn't realise the gun was operating far under pressure and not atomising properly to the point where air bubbles were still in the paint after landing on the panels.

An awful lot of sanding later I bought a regulator for the gun itself and hey presto, I filled my garage with overspray initially but I didn't care, because it worked!

Thanks again for all the help and suggestions - one black Merc CLK coming up