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For those who´s read my finish spraying try. here´s a shot of how my problem looks ! perhaps this might be of help resolving the problem. I will be scraping the finish off and start over. but for my future spraying it would be good to know how to fix this. ( if its not the problem we though by just reading my previous post ) " Laurent and others" after seeing the photos it might help.
its like this all over.
Lars

It may not be a "Spray" problem so much as a "Varnish problem.

The problem I run into with Varnish is the insanely long open time -- it stays sticky for 4-6 hours for me...

If I want to get a nice level finish -- I have to level sand to get all the lint and dust picks out.

If you are getting bubbles -- thin it out with more reducer.

The other solution I found was to brush in the Bathroom -- run the shower to wet down the air and use a little spray bottle to spritz down the walls... This pulls down residual dust and lint. It isn't perfect, but much better.

Another solution I have seen is to make up a "Paint booth" in a basement corner -- use plastic tarps for "Walls" -- you wet the inside down generously immediately before painting to keep dust down.

Block off the AC duct, brush, then close the door when you leave....

Don't give up -- you are pretty close.

Best of luck

John

Thanks John. Yes I guess it the varnish. so enoying though. the specs seem to come from nowhere.

Lars

Lars, in your other post you described these specks as "craters". In the photo that's what they look like too. Here in the states, we call those "fish eyes". They're caused by contamination of the surface with something that prevents the finish from flowing out. Silicone usually gets the blame for this, but a lot things can cause it, including moisture condensation, (or droplets of over-spray if you mist the booth with water to knock down the dust. Water droplets can come through your airline too. If its water, just sand back, put a dessicant, or at least a water trap in your air line, and make sure you spray when the air is warm and dry. If the problem is silicone or some other contaminate you'll have to get that off the surface, or it will just happen again when you respray. Washing the bare wood with a sequence of solvents usually works. I would try naptha, then alcohol, then acetone. (Don't let these touch the finished areas. Good luck.

As Eric is getting to...
It helps if you can identify the exact problem you are having.

Varnish that is too thick can spit and leave clumps and bubbles that don't lay down.
Too cold also causes this. Varnish also gets very "Clumpy" if you don't thin it enough.

For lint and dust picks... If you shine a light at a low angle across the top -- you can see little "Hairs" sticking out.... though at 1st you would swear they are bubbles. You can also feel the hairs and little high rough spots when you lightly brush your hand across the top... The 2nd symptom is that you level sand and they are gone, then put on another coat and they crop back up in the exact same spot. Only thing that has ever worked for me is a razor blade to "shave" the lint.

I have honestly never (YET) had a problem with fisheye... It's the dust that kills me.. but I know people who have had endless bouts with fisheye.

Thanks

John

wow. Eric ,John both you are spot on here. I did water the whole place right before I started spraying, so much chance is that some water might have caught the surface. also John, the "hairs" are sure there !! will do what you suggested on this.



YES !!!
and fish eyes . . WHY DID I PICK OIL VARNISH !!! - well good practice though.

So- lets say I sand the guitar 24 huers after spraying. Then to be on the safe side from fisheyes, what do I do.? run a rag with napha over the top ?

Lars

You need a spotless room to spray pretty much any finish, but varnish is worse due to the longer time it's tacky. If the room, your spray gun, and your air are really clean it could be your clothes. I wear a tyvek suit when spraying any finish so dust and lint from my clothes doesn't get in the finish. You need to strain your finish as you pour it into the gun. It's also best to have a filter in the gun also. One of this type filters works good in a gravity feed gun.


I use 3M's PPS system which includes a strainer the fluid goes through before entering the gun. I've had fisheyes but never with oil varnish.

As you've already said, you need to wait longer than 24 hours between coats.

Laurent and others, is it possible for varnish to develop bubbles from trapped solvent like lacquer?

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Thanks woody. I do filter the varnish really good before I put it in the gun. I blow my clothes before entering the area of spraying, hair also. wet the floor and walls. I am using a low pressure Iwata LPH-80 gun "Using only 1.8 cfm at 13 psi"
http://www.iwata-medea.com/index.php/products/lph_80/
Its more like what John said. small "hairs" and/or tiny clogs.
I will give it a last shot tomorrow with a really fine thin layer. and see how that goes. if not I will give up due to time ! and get me some nitro.
I have also ordered a 1.2 nossle for the gun instead of the 1.0 that I am using now. also ordered some high quality filters. so tuesday/wednesday I might have some more goodies to try out.

Lars

For the lint component, don't forget to cover your head. I had a lint free enclosure, but I kept getting lint. Then I realized that it was probably dandruff. Anyway, dandruff in the finish likely will rub down to invisible when buffing.

Never experienced fisheye with oil varnish, it's a pretty forgiving finish regarding contamination, unlike lacquer. I do not see anything resembling fisheye on the pic either.
The long curing time means you'll always have a bit of dust sticking to the varnish, it seems there's a mutual attraction that never ends. The good news is those sand out readily as they are on the very surface, and not embedded in the finish.
It's hard to see on the pic but Woody is steering you in the right direction. It doesn't look so much as specks of dust than small clumps of half-cured varnish spat by the gun.
My first question would be: do you flush and clean your gun after each session? Then, how do you clean it? I assume you strain the varnish, although for the first few coats it isn't absolutely necessary. But a clean gun and finish container are mandatory.

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Make sure that the varnish is not building up on the openings in the nozzle of your gun. If it builds up there, they can break off and deposit on the surface, looking just like little gobs.

Has anybody tried Japan drier to speed up the drying time? It won't cure any contamination problems but it can cut way down on the tack time.

Yup I was betting on this at first to. also a local car finisher guy told me the same thing. So I cleaned the gun throughout with thinner. took it all apart and put it back together. fixt new varnish 75 % napha and 25 % varnish. Then same thing happened. !! small lumps. and yes it does look as half dried varnish. But how is this possible. the varnish it self looks clear and nice once mixed with napha. I am clueless. also there sure are fisheyes on there. but those are from the wettening of the floor and air before spraying I think.

Lars.

Water is not going to contaminate your varnish, period. If there is water ot moisture on your guitar, wipe with a paper towel and let dry a few minutes before cleaning with a tack cloth and spraying. I clean the varnish dust with naphtha on a small (clean) rag, after blowing it with an air gun, before tack cloth and spraying. IMHO there is no need to wet your floor, unless you spray in a barn…
I do not understand this. Also, what do you call "thinner"?
If there is just a bit of varnish left in your gun and/or paint container, it will either clog your gun, or go through as small lumps. Varnish, unlike evaporative finishes, is not dissolved by its solvent or other varnish once cured. In other words, liquid varnish and cured varnish are chemically different. Only strong solvents like acetone and lacquer thinner will "melt" cured varnish, and not very well.
After spraying I pour whatever varnish left back in the can, flush the gun, clean the finish container with paper towels and naphtha, pour a bit of naphtha in the container and shoot in a canister at the lowest pressure available. I take the gun apart for a full cleaning after maybe 10 or 12 sessions.
Now, is this your "old" finish on the pic, or did you start over?

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Its my old finish. But its still there. havent started scraping yet. "been busy playing football with my son"
I use laquer thinner for cleaning the gun. and clean it good each time I use it. ( not full apart ) but nossle tip etcv I also make the L-thinner go back through the cup " sreving the tip almost of and press lightly on the sprayer. check out my gun info, there cant be almost anywhere the laquer can get stuck its like a one hole passage ! its not like a full set gun like the iwata 400 etc. its a small semi minigun.

Ps- I do wish I lived in barn .

Lars.

Forgo the lacquer thinner and the small lumps will go away.
Also you probably don't want to breathe lacquer thinner, or even spray it in the air where you and your family live. My 2¢…
And you should stop confusing lacquer and oil varnish: two very different beasts.
Proper solvent for any oil based varnish is either naphtha, mineral spirits or (real) turpentine. Or the solvent made for your particular varnish, which is probably naphtha-based. I vavour naphtha for spraying and cleaning as it flashes quicker than the other solvents.
Lacquer thinner makes oil varnish "gel", take a bit of cured varnish and put a drop of lacquer thinner on it and you'll see what I mean.

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I have had best luck cleaning out wet varnish with the old fashioned, cheap "Stinky" Paint Thinner... Nothing works on old, crusty varnish.

Odorless mineral spirits and Lacquer thinner are almost useless with varnish... Never use Alcohol or Acetone -- it just makes it worse. You may as well be using water (Literally... Polar solvent + non-polar coating = doesn't dissolve) .... Buy a couple gallons of cheap, stinky, odor-full paint thinner....

Take heed of what Laurent is saying here.... Cured varnish in your gun may as well be Epoxy or Poly Urethane -- It polymerizes and "Cures" kinda like an epoxy.... Totally different than an evaporative finish like Lacquer or Shellac which just dries out over time.

2nd...

You may have the wrong nozzle for thick and gooey coatings.... Many Auto type spray guns have nozzles made for shooting heavily thinned Lacquer paints that flow like rubbing alcohol... and you are trying to shoot slimey pancake syrup....

I would 1st try thinning it out even more. See what happens... If it isn't any better (or gets worse from too much solvent)... talk with the car paint guys about what they would use to shoot thick and slimey coatings like high solids epoxy....

Thanks

John