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Bubbles in paint finish

Started by _Eddie_ , Feb 13 2006 11:56 PM

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13 replies to this topic

#1 _Eddie_

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Posted 13 February 2006 - 11:56 PM

I am getting these tiny little bubbles or little balls in my finish and I can't work out what is causing it. As soon as a coat is laid down, the paint seems to bubble like a lava pit, or like soup in a sauce pan simmering on high- except the bubbles are small like a pin head. Some of the bubbles disappear when dried whilst others stay.
I've been using the process of elimination to figure out what it is and so far I've found: It isn't the paint, it isn't the gun, it isn't the surface. Which leaves me with either the thinner or the compressor. Just wondering if anyone knows what it could be as it's really shitting me to tears here. :banghead:

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#2 GML-31

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Posted 14 February 2006 - 04:05 AM

I assume you have a good watertrap on the compressor???

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#3 REDA9X

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Posted 14 February 2006 - 06:01 AM

I agree with above. What sort of compressor? Is it running all the time? small tank, old tank? do you drain it every day? Get a good reg with a water trap and filter, and don't put it close to the compressor, put it closer to the gun. You can also get a small filter that clips into the gun.

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#4 _Yella SLuR_

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Posted 14 February 2006 - 06:36 AM

Ideally water trap should be 6.0m from the compressor, with the line running back down hill to the compressor, so any condensation in the line runs back into the tank.

What bit of the car are you painting? Paint fried up when I tried the engine bay, but that makes a little spider web sort of network in the paint.

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#5 _MYLJ_

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Posted 14 February 2006 - 08:19 AM

sound like one of 3 thing

1- moisture in the air(is it humid were you are painting), or moisture/condensation in the air line ,I've had this happen on hot days when I've hosed the concrete floor down prior to painting (the compressed air coming from the tank to the gun gets cooled down in the hose on the cool/wet ground causing condensation in the line, so even if you keep draining the water out of the compressor it may still be present at the gun) {best solution is keep the hose elevated and dry, and out of direct sun light}

or you have water in your compressor tank

2- contaminants (probably silicon particles or something similar) in the air , are you painting in a booth? have you washed down the ceiling and walls of where you are painting the car? if you have ever used any silicon based products (armerall etc) in the area you are painting in it will sometimes cause reactions , even if you haven't used them in that area for months/years it can still come back to haunt you, even if you have washed out the area.

3- what prep-wash are you using? and how are you using it? the surface may be clean after you prepwash it down but if you use it excessively it can leave a residue on the surface even if it appears to have all dried off, use prepwash on a clean fresh rag and keep it to a minimum. never use gunwash etc to wipe down the panels prior to paint.

hope that helps

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#6 _kaz from adelaide_

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Posted 14 February 2006 - 11:39 AM

i got in heaps of shit when Ruby was repainted as my Grampa taught me the wonders of silicone when i was a youngster. Ruby was almost held together with silicone b4 her restore. I think he added something to paint 2 stop this, but i still have a few bubbles here and there.

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#7 _Eddie_

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Posted 14 February 2006 - 12:17 PM

I've been draining and recompressing the air each day before I start the job. The area I am painting is the metal dash, but the same problem is evident on other panels. The dash has been taken back to bare metal, sprayed and again, taken back to bare metal once more after realising it f**** up. I have one water trap at the compressor (about a foot away) and one at the gun. No sure how big the compressor is, or it's brand or it's power output but I'll find out today. I think it's under 10 years old. The area was initially cleaned with KnH prepwash and wiped over again with another clean rag. The paint has bubbled in 50-60% humidity with the dew point temperature around 2/3rds to 1/2half of the outside temperature. The bubbles seem more evident in the clear coats than in the colour coats. Not sure about the silicon but I'll try a panel outside.

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#8 GML-31

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Posted 14 February 2006 - 01:23 PM

you can buy silicon drops to add to paint to stop the reaction.

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#9 _Yella SLuR_

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Posted 14 February 2006 - 03:37 PM

Additives or contaminants are more likely to cause fish eyes rather than bubbles. Definitely a problem with moisture in the paint.

Um, when compressed air heats up and not able to hold as much moisture, that's why you use the moisture traps. Don't understand it myself, but that's what the manuals say. I just take their word for it.

Other thing can be humidity in the air when painting as already suggested as well.

Dunno if it helps, but I also drain the trap regularly, as soon as I can see any built up water.

Edited by Yella SLuR, 14 February 2006 - 03:38 PM.

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#10 _Eddie_

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Posted 14 February 2006 - 04:02 PM

I've used a different brand of thinner and a different clear coat which seems to have nullified the curse. Not sure exactly why just yet but I'll suss it out and keep it posted... just anyone else happens to run into these.... shinnanigans

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#11 Loui

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Posted 14 February 2006 - 05:41 PM

Its called Solvent Boil

Apperarance: Small craters in the paint film formed by trapped solvent being forced to the surface and popping

Causes

Spraying in warm moving air
Air pressure too low
Incorrect flash off time before baking
Applying heavy top coats
Oven too hot or heat source too close to components
Using incorrect thinners

Most proberly caused by dodgy thinners or spraying in too hot area
About 25 degrees C ya want

Also you could try a retarder to slow the paint drying time

Cheers

Loui

Loui

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#12 _Yella SLuR_

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Posted 14 February 2006 - 07:33 PM

Think you might have something there Willis. Have never done that, but yeah, I think you might be right. Usually takes about 2-3 coats to get solid colour. If you try to get solid colour in one coat, your gonna end up with problems, or if you don't allow sufficient time between thick coats. Slowly, slowly catches the monkey.

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#13 rodomo

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Posted 14 February 2006 - 08:13 PM

I painted something (I forget what) and had silicone pits all through it. It was the rag I had used with the prepsol.
RACV MAN

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#14 _Pete_

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Posted 14 February 2006 - 10:49 PM

A close up pic of the dilema will be the best way to work out what is actually the problem,

I'd be guessing humidity blisters due to the fact that the weather up here has been horrible for painting acrylic in at the moment.

What everyone has mentioned could definately be a possible cause/solution, a pic will get it sorted out.