I'm hoping this starts a really good thread on spraying.
What has your experience shown you to be the best cut of shellac combined with tip size when HVLP spraying? I Understand there are many other factors, but I'm trying to narrow these down first. I've heard/read that success varies widely with trying to spray shellac, but given the workpiece (many nooks/crannies) that I want to spray. I *will* be dewaxing the shellac which is advertised to be dewaxed (my own experience at work in this decision).
That's what I'm afraid of (fast dry and overspray). I've mixed a 1/2# cut but haven't tried it yet.
I don't like to think this way, but it's a game table base (pedestal), so maybe the state of mind of the people who do get to see it will keep them from being too critical... (I hope).
Shellac is about the only finish I use, and I always spray it.
With an HVLP system overspray is not a problem, IME.
If you are not planning on using anything but shellac, buy the three pound cut and thin it down to 1 1/2 with alcohol (I prefer to use this cut when spraying, but YMMV) ... experiment.
3 pound cut is what you get out of the can for the standard, althouugh I've seen 4 and 5 pound cut at paint stores, and the "sanding sealer", out of the can should be a 2 pound cut.
You really don't need the dewaxed if shellac is all you're using ... the dewaxed being essential for compatibility with lacquer, poly and other top coat finishes added post shellac application.
The Zinnser sealer is dewaxed and works well when sprayed and can indeed be used as the finish coat.
I just generally use the regular BullsEye amber 3 pound cut, thinned to a 1 1/2 pound cut with isopropyl alcohol (depending upon the temp/humidity) sprayed on for the final coat.
I find I have better application on extremely high humidity days with isopropyl alcohol, but the Borg denatured works fine 99% of the time.
IME, with humidity, what you're worrying about is blush.
With isopropyl alcohol so cutting you need to pay particular attention to the shellac drying before it hits the surface. If that is a problem, simply cut your material flow down a bit and spray closer to the work (with HVLP).
Spraying shellac is not that difficult, as a matter of fact, it is easy and forgiving with an off the shelf, $100 HVLP unit. A couple of minutes with a scrap piece to make sure material flow and distance is right, and spray on.
On Tue, 05 Jan 2010 14:31:50 GMT, the infamous "Joe" scrawled the following:
Have that damned cat NEUTERED!
That's some pretty juicy stuff. Not having sprayed it, I'd suggest a retarder (so the sprayer doesn't dry it before it hits) and a pretty stiff mix to begin with, like a 5# cut (to reduce runs.)
-- Society is produced by our wants and government by our wickedness. --Thomas Paine
1 1/2# cut of shellac is pretty standard for spraying shellac, IME.
Here's how I view the rest of it, through my 'hands on' only experience:
Evaporation is obviously slower when the humidity is high due to the higher moisture content in the air.
Blush is caused when the water in the thinner doesn't evaporate readily and the sprayed surface dries.
So one method when spraying alcohol cut shellac in humid climates is to either allow evaporation to go faster by spraying on days with low humidity, or reduce the amount of water in the thinner (alcohol) itself ... mitigating, somewhat, the humidity induced slower evaporation as a factor.
An anhydrous alcohol has a low(er) water content. I usually use a 99% anhydrous isopropyl alcohol to cut shellac when spraying in this Gulf Coast climate on really humid days.
As I mentioned earlier, a possible problem spraying with thin alcohol cut shellac is the spray mist may dry before it actually hits the surface of the project ... particularly true with cheaper HVLP guns where you don't have a lot of tips available to fine tune the spray.
But you know, I really don't know that much about spraying and am not a finishing expert by any means ... I do have a background in Chemistry, so understand the dynamics and physical properties/reactions, but I'm a trial and error kind of guy in the area, and try to use what I do know to make changes until it works for me ...
On Wed, 6 Jan 2010 00:55:49 -0800 (PST), the infamous " snipped-for-privacy@aol.com" scrawled the following:
--snip-- Excellent, Naily.
I'm going to print out this entire post and hang it with my gun for enlightenment the next time I spray.
You condensed into one post what Andy Charron took 2 entire books to say, Robert. Goodonya. (I have his _Spray Finishing_ and _Water Based Finishes_ books.)
-- We rightly care about the environment. But our neurotic obsession with carbon betrays an inability to distinguish between pollution and the stuff of life itself. --Bret Stephens, WSJ 1/5/10
On Wed, 06 Jan 2010 18:39:58 GMT, the infamous "Joe" scrawled the following:
That's the Wreck DEFEATIST Spirit, Joe! Carry on.
-- We rightly care about the environment. But our neurotic obsession with carbon betrays an inability to distinguish between pollution and the stuff of life itself. --Bret Stephens, WSJ 1/5/10
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