preval sprayer

[ashemando]

Does anyone have experience and opinion of these sprayers?
Are they functional enough to use to complete an instrument? Thanks.

[8ch(pl)]

They have been on the market for quite q while.

I used them about 20 years ago when I was an Aircraft Refinisher. They are good for getting that special formulation on a surface without using a gun. They do not give any better spray pattern than a Spray Can.

If a person wanted to lay down a coat of shellac sealer a Preval Sprayer would serve.

[mario515]

there is some threads on this by one of the board members(I forgot his name(nice guy too very helpful,,,, Oh wait I got it,, Yonkle,, yeah thats it)) it also has some pictures of his work with Preval for your perusal

[Bill Snyder]

The only finish I tried to apply with a Preval sprayer I ended up stripping and redoing with a pad.

[Dale Ludewig]

I wouldn't recommend it from my limited experience with them. They just don't have any air pressure of consequence behind them to atomize the finish enough. If you don't have a compressor type setup, or could borrow one, I think I'd either brush on a varnish, french polish (you should lay down a barrier coat of some sort), or use the aerosols from StuMac, although I haven't actually used them. But I hear they're not bad. There's always tung oil, polymerized tung oil, and such.

[Fretbear]

A very good nitro finish can be achieved by a skilled/careful first-timer using aerosols. Stew-mac doesn't have a very wide choice, but if they have what you want, they would work well. I did a black-face with stained sides sealed in clear spray lacquer, and was able to buy matching brands of black primer and semi-gloss black from an industrial finish supplier, which I applied sparingly to the top with the rest of the instrument sealed off. I love the resulting semi-gloss black finish, and while the product was not sold for musical instruments, it worked flawlessly. After a long curing, it will look like orange peel, and then you can buff it up to a beautiful shine using fine wet and dry sandpapers and finish up with fine polishing compound, being carefull not to sand through your finish.

[mandolinplucker]

I've used Deft nitrocellulose laquer for small projects, finish repairs on guitar and mandolin and finished a mandolin with it. I've had good results with it and for small stuff it's easier than mixing, filling the spray cup, spraying,and cleaning the sprayer. I'm not a luthier and don't know the longterm results of using this product,so if I'm screwing up please correct me so I don't continue to screw up or suggest that others do.

[ashemando]

Obtained where?

[thistle3585]

Tony,
I use Deft in my shop along with the mandos I've built. I believe Bill Busmann does also. It is available at any hardware store. Search the builders section with the key word Deft and you'll get a lot of info.

[mandomaker]

Dale mentioned a barrier coat. I have been thinking about this too much lately, but it seems like it might be important. Does anyone have thoughts to share? Gamboge, egg white, other substances? It seems like preventing oils or laquer from soaking into the wood would help to achieve that "old sound" if your wood is aged and you used hide glue. Any taken an electron microscope and spectral analysis to a Loar wood chip? Might be overkill.

[mandolinplucker]

Mandomaker, from what I have learned from researching "french polishing"; the barrier coat is a heavy coat of shelac applied with clean cotton pads to the bindings and parts that have been scraped to keep from rubbing the die back on the areas that you don't want to redye. Dale is welcome to correct me if I'm wrong. As far as finish goes- my skill level is still in the novice area so I hold to the KISS theory. When I am capable of building a masterpiece I will worry about mastering or experimenting with fancy finishes but for the forseable future I dont see a downside to a sprayed on laquer finish. It's easy,almost fool proof, good looking, durable, and as far as sound goes make it as thick or thin as you want. I try not to make things any harder than it has to be.

[Dale Ludewig]

Actually I'm referring to a coat of something that is not the same solvent base as the stain/dye. This is not just to protect the bindings from getting the color pulled back onto them, but also to protect the dyed surface of the wood from getting dirty or damaged while you're scraping the bindings clean and also to prevent the sunburst from being smeared from the FP. I'm not experienced using shellac as this "barrier" coat. Someone else will hopefully chime in on that. If I'm using lacquer as the finish, I usually use vinyl sealer as that first coat. If I'm varnishing, I'll use a varnish. If you're going to use Deft or a glossier lacquer in an aerosol can, a light coat of that would work. Do not use varnish under lacquer- not compatible. Hope that helps (and makes sense).

[amowry]

I use shellac as the sealer coat under French polish-- I spray a few light coats before untaping the binding, then scrape the binding, then spray one or two more coats of shellac. It redissolves my dyes to some extent, but as long as the coats are light it doesn't redistribute them. Once the sprayed coats dry I can French polish safely without moving any dye around.

[amowry]

I forgot to mention-- I have used a Preval to spray the sealer coats, but I don't think I'd want to have to finish a whole instrument with it.

[mandolinplucker]

I was having trouble with tape pulling up spruce splinters after binding. Someone on this board suggested that I put a spitcoat of laquer on prior to binding. It can be sanded off prior to staining and it worked for me- no more splinters. Just another reason that I lean towards laquer. I haven't said it enough-- Thanks to all of you who take the time and effort to answer all of the questions that us novices ask. Knowledge that is passed on to others is a valued and appreciated resource.

[Dale Ludewig]

Tony- there's an easier way to deal with this tape problem, at least in my experience. I use the binding tape from StewMac. I know others use rubber bands, etc., but I've grown to like the tape. When I put the binding cement on the ledge I only go about 4" at a time, squeeze it tight and wipe it off with a paper towel. (See Benedetto's video). Then when I go to take it off I use a heat gun and gently heat about 4-5" on the top- no need to worry about the sides. This softens the adhesive and if you get the tape off while it's still warm you should find there will be no pulling out of the grain. If you put a sealer coat down before you bind you have to be really careful that you get it all off or you'll have dye problems. YMMV.

[mandolinplucker]

Thanks Dale. I was worried about not sanding all of the laquer off before staining. I didn't have a problem this time but I can see that it could happen. Those splinters look small till you start sanding them out. I had to leave some because to sand them all the way away would thin the top too much. I'll try the heat gun next time. Live and learn. Thanks again.

[Dale Ludewig]

You're welcome. And you're right- those "small" splinters could be deeper than you think. Best to avoid them altogether, especially after all the work you've put into the instrument already. I'm sure none of the other builders who post here or not have ever made a mistake they had to deal with later. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif

[dfrosto]

I've finished a few mandolins and guitars using the Preval sprayers. It can be done, but I don't really recommend it unless you have no other options. Its hard to lay down a thin even coat with it, since it requires so many passes to cover the expanse of the instrument.

[Yonkle]

Yes I have done 4 mandolins with a Preval sprayer. If you are using Lacquer and have no spray equipment, I would just get the stuff in spray cans "Deft" works well.
I have no spray equipment, so for shellac my first time I did a french polish applying it by hand, and got the job done, but this is hard work and it takes experience to do it right. So on my next I used preval sprayer to get the shellac on, then flat sanded, wet sanded, and rubbed it out, similar to how you would with lacquer, and got fine results. (As far as the spray itself... it won't spray even close to a real spray gun, it's OK but kind of spits the shellac out and it's not real consistant in the mist and you have no control of how fine a mist, other than cutting you shellac with more alcohol. The thinner the cut the better it sprays. I used a 2lb cut and it is a bit heavy for the preval so I thinned it down and but on more coats. Basicly if you can get enough coverage to sand it flat with out breaking through you will be fine. If you are only doing 1 or 2 mandolins, go for it, it your plans are long term building, get some equipment. You will need 3-4 of those recharge units to get enough on. Here is a close up of my F4, Preval used here. JD