nitrocellulose

[hughie]

I have run into a bit of a problem with this. Spray it no worries, low pressure gun around 15psi , thinned down ok etc. Goes on nice and clear but when it drys I have some white spots here and there. Cleaned the gun out several times, taken it back to bare wood a couple of times, tried it over DO, still have the white spots.

I would appreciate some feed back from learned Gentlemen of this forum as where I'm going wrong.

[router]

It sounds a bit like you have not wiped all the sawdust off the item being lacquered.

How much are you thinning the lacquer down?

When you are putting the lacquer in the gun are you running it through a strainer, the lacquer and/or the thinners may have some impurities in them.

Can you post a picture on the job so that we can see what it looks like.

It could also be moisture causing the problem, in the air or in the air line to the gun.

Router :U

[dai sensei]

I've had problems with NCL sometimes when I have too much thinners in it whilst spraying it too thick, if not white spots, I get dimples as it dries. I have also experienced white blooms when the humidity is too high, but that is more a haze rather than spots.

[mark david]

Hi, are you using fiter/dryer in your spray set-up
Maybe you are getting some moisture or contamination
Not sure exactly what finish you are using, have you tried Becker Acroma DM307?

[Mobyturns]

Neil,

I am no expert on NCL or spraying but I have experienced the white spots before when using a cheap air brush to spray small turnings. Sometimes I suspect it was some of the lacquer not atomizing properly through the nozzle and drying on the tip then being transported onto the surface of the piece. I guess there was sufficient thinner in the wet coat to only partially dissolve the NCL. Or it could be over spray being carried on to the work piece?

White spots are generally from water trapped in the finish & so many variables can produce it, nozzle size, nozzle pattern, thinning ratio, air pressure, no filter, insufficient film thickness, humidity, temperature .... Sometimes you can remove the blemish by rubbing with solvent to redissolve the finish to free the trapped moisture.

[Evanism]

White dots is water.

Get a dryer for the compressor and don't use that hose any more - it's contaminated.

[Bob38S]

Length of hose and distance between gun and regulator/water trap can also be a problem.

How often, if ever do you drain the compressor tank?

[wheelinround]

Or just drain the litre of water out and flush hoses with metho :;

[hughie]

It looks like water is the problem, something I didn't think of :doh: should have been the first thing, never mind. I have a 10m hose and a 3m hose with the water trap at the end of the 10m then the 3m and I guess my water trap/regulator aint doing its job too well :) Contamination I would doubt if the water will cause any lasting damage to any of the hoses. I have been using the hose fairly extensively today so it will be well blown out and dry . No nitro spraying as its raining too much moisture around, just a lot of blowing down. No strainer for the gun thats been done previously and kept in a separate container.

M,nay thanks for all who answered, much appreciated. :2tsup: