Spraying Varnish

[Don Z.]

Does anyone have any experience spraying varnish with an HVLP gun? I was wandering around the chandlery today and noticed that Epiphanes sells a "spraying thinner"... Which got me to thinking.

Also, I noticed Epiphanes has a drying agent which is supposed to speed drying time and make for a harder finish. Any experience with that?

First experiment will be on some furniture. Actually, an Arts and Crafts piece and all those 1/2 inch square spindles make me loathe to use a brush... hence the HVLP idea. Any input would be appreciated...

[thechemist]

Search out a thread titled "spray varnish". A lot of what you want to know is in there.

[Concordia41]

I've used Epifanes accelerator with good results. Seems to make it go "off" before it has a chance to sag, run, collect cat hair, or otherwise self destruct. Have considered spraying, but would appreciate it if someone else took the plunge on this.

Seriously, I've got a growing collection of pieces that I've just made myself leave alone because after multiple "final" coats there were still specks of dust or whatever, but in the back of my mind I've been thinking I could turn the garage where we're storing the finished pieces into a spray booth...so anyway, let me know how your spraying goes http://media5.hypernet.com/~dick/ubb/wink.gif

[Concordia41]

Thanks Chemist. I also notice there's a good hint in that thread about saving good information like that to a "tips file."

Now let me go read the dozen or so other posts that came up on that interesting search...

[Don Z.]

Thanks Chemist... That thread is a good reason why I began to think this way... but I guess my better question is, knowing how thick Epiphanes is (and it is my favorite varnish, not yet having tried Rivali) does the "spraying thinner" really work? I guess I'll just have to try it and see. Thanks again...

[thechemist]

Oh, one other thing......they are doing some competitive varnish tests around here, and Epifanes is a profoundly softer, more flexible varnish than Captain's. Not that either is better or worse than the others, just different. I recommend that to see how mechanical properties of one varnish compare with another, and how much Penetrol to add [or not] to improve without screwing up, and how something-or-other affects cured properties, paint on a sheet of glass. Glass places will gladly cut you a few three-by-twelve-or-so pieces. Many samples can be done this way, and you will immediately see things such as a too-thick film not curing in a timely manner. The cured films can be lifted with a razor blade to assess film properties, and stripped off for glass substrate reuse, if you really wanna get into it.

You will also see that [only for example, no comment one way or the other about a particular brand] that since Epifanes has a viscosity of about a thousand centipoise, it brushes out with a typical natural bristle brush in about a five-mil film thickness. Captain's, having a viscosity of about 350 centipoise, brushes out in a film of about 2 to 2.5 mils wet film thickness [The relationship is not linear].

Epifanes has a solids content of about 65% and Captains 55% [neither is good or bad as such....the resin systems are very different....don't judge for solids content only] and so Epifanes ends up with a dry film thickness maybe twice that of captains. Each cures well in that wet film/dry film thickness. Neither cures well if applied in a wet film thickness of twice that. You can see the "hard-to-the-fingernail-scrape" test results in about three days.....

Rivali, I dunno about, and a spray reducer must cut viscosity efficiently and evaporate quickly. A brushing reducer must be inefficient in cutting viscosity [so the wet film thickness does not rapidly drop with small solvent additions or evaporative losses], and must evaporate slowly, so one has time to brush out a liquid film of not-rapidly-changing properties. Not all manufacturers appreciate this.

Once you see what the varnish turns out like, and can do the experiments where many side-by-side results can be evaluated, you can make a more intelligent choice.

[Peter Sibley]

Chemist.....could you comment on the suitability of clear spray laquer(acrylic) for internal use aboard.I use it all the time in my furniture finishing ,its cheap, the results are excellent and I know how to do it. How will it stand up to the high humidity of life aboard?

[Bob Cleek]

Actually, as for Arts and Crafts pieces, I believe Stickley and others did NOT varnish their pieces, but rather "smoked" the oak with amonia, which imparted the characteristic color and finish of original Craftsman wood work. I've read about the process and it sounded nasty. I've never been a big fan of amonia fumes. Sounded interesting, though. Maybe Chemist knows something about the process.

[Charlie J]

fuming oak - build a plastic box large enough to contain the piece- it doesn't need to be strong, but must be relatively air tight (taped seams) Put the piece to be fumed inside, place tray of ammonia inside with it and close it up. When the wood reaches the color you want, remove it. If you go to a Blueprint house and ask nice you may be able to get enough of their ammonia for the job- use much caution- that is very much stronger stuff than house hold ammonia is. I got a couple gallons from a Blueprint shop that shut down. Goes a long way http://media5.hypernet.com/~dick/ubb/smile.gif

[jeff pierce]

Reminds me of back in my high school days, when I took a drafting class in which we had a blueprint machine. Every year, the instructor would tell us not to stick our noses over the ammonia reservoir. Every year without fail some bozo would try it and wind up on the floor.

[thechemist]

Lacquer.....inexpensive, attractive appearance, easy to repair, used for thousands of years, methinks.....

Adhesion to wood is okay on interior house-on-the-hard furniture well-taken-care-of.......but the modern acrylics are esters and an ester is something formed by reacting an acid with a base and eliminating water, so in the presence of water the reaction tends to go backwards, decomposing and degrading the lacquer. Wood fibers will also swell from absorption by diffusion of water through the lacquer film, giving release to the lacquer film. Put stuff on coasters, use a tablecloth if this is a dining table, keep spilled wet food , etc, off it.


[This message has been edited by thechemist (edited 10-05-2001).]

[Don Z.]

Bob, you're right... fumed or oiled oak for A&C. But I used Honduran Mahogany (would you believe it was cheaper? Or near enough as to make no difference) and the couch is already Epi's...

I thought about lacquer. Used it once. I had a nice cherry table. Finished it, and put a lamp and a small (.50 calibre) naval gun on it... Learned that lacquer has no UV resistance, as now, the table is darker except where those two items were. Also, I never worry about spilling my drink on the couch...

[Nicholas Carey]

Originally posted by Bob Cleek:
Actually, as for Arts and Crafts pieces, I believe Stickley and others did NOT varnish their pieces, but rather "smoked" the oak with amonia, which imparted the characteristic color and finish of original Craftsman wood work. I've read about the process and it sounded nasty.

It is nasty. Not to mention hazardous. Basically you build a tent. Put the piece to be fumed in it, along with a shallow dish (like a pie pan) full of, um, strong ammonia (30% or better). Close it up and go away for awhile. How long depends on the wood and the ammonia. You need to experiment as each billet of wood is different.

The way it works is the ammonia fumes react with the tannic acid in the wood (that's why it works really well on oak.)

But it's not a finish per se -- it's a way of coloring the wood itself. You still need to apply a finish to the wood.

[Charlie J]

isn't that what I just said?

[GROOVY]

I would try spraying the arts and craft stuff with lacquer anything but varnish...
I tried to spray spar varnish thinned with the special thinner reccomended ten percent thinned, still was too thick to spray and dried too slow to prevent sags. Have used foam brushes for the eleven other coats. With a foam brush I had just a few small mistakes that were easy to sand down, after spraying I had several biguns.. took longer to dry and sand.. Of course they told me not to spray it..but I just had to learn the hard way!