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I have begun to spray my 4th dreadnought. I used a spray gun on the 3rd for the 1st time and had a few problems. The main issue was that I did not get enough finish on the guitar, which became evident as I sanded.
How much would you consider is a reasonable quantity of nitro to finish a guitar?
I am using a small HVLP touch up gun ( I have plenty of time!!) running off a compressor, so there is not a lot of overspray.
I am deliberately going on thicker this time, with the odd little run happening (technique!!).
Lacquer is thinned 2: 1 (lacquer:thinner).
I have done 4 coats and used about 400ml for body and neck.
Does that sound about right?

Frank

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Here in the Uk I find you don't want it too hot for spraying Nitro. If it is warm I add some reducer to slow the drying time.
I have also found when it's very warm I have had "solvent pop" on the finish. these are small bubbles of solvent gassing from the finish leaving pin size white dots.
Not very nice when you have just sprayed a Rosewood guitar.
Also make sure you use the correct thinner for the lacquer. Hope this helps.

Frank M8 there is an excellent guitar finishing with nitro free-for-download Instruction manual on Stew-Mac's site. This is their kit instructions but in the manual is a nitro finishing schedule that I used and it worked great for me:

http://www.stewmac.com/shop/Kits/Acoustic_Guitar_Kits/1/Dreadnought_Guitar_Kits/Instructions/I-5295.html#details

Interestingly they have you spraying 9-12 coats where most of the first 6 coats get sanded away in the leveling process. According to Stew-Mac and Dan Earlywine 3 coats a day one hour apart. They also talk about "scuff" sanding to promote mechanical adhesion each day.

It's worth a read and did a nice job for me.

I spray McFaddens right out of the can, no thinning. It seems to take about a quart per guitar.

Back, sides and neck: 5 coats, sand, 2 coats, sand, 2 coats, let cure 1 month, sand and polish.
Top: 3 coats, sand, 1 coat, sand, 1 coat, let cure 1 month, sand and polish.

Mark

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I can finish 2 guitars with a quart of cat urethane and still have some left over. This includes three spray sessions over a three day period. With nitro you should be able to do better than that as there is no waste like with cat urethane.

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I spray McFadden's right out of the can and believe two guitar bodies per can is do-able.

I usually spray two wet coats of sealer (thinned 1:1) wait a day and level lightly with 320 wet. Then shoot two or three wet coats of lacquer (no thinning) per day for three days with a light scuff sanding at the beginning of each day. Then wait about a week and sand aggressively enough to get level but not through to the wood. This takes some practice and patience to know when to say "when". Then two wet coats and wait at least 2 weeks before final sanding/buffing.

I use a touchup gun I bought at Walmart or Lowes (not one of the HVLP guns) used for painting cars and spray at less than 20psi and try to avoid overspray. At the lower pressure with more flow at the tip it can be done just be careful not to go too slow or you'll get runs. The unthinned lacquer helps reduce runs too.

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"We might not be big but we sure are slow"

I spray McFaddens unthinned with a minimum amount of butyl cellusolve to prevent blushing. The amount of BC depending upon the RH at the time of spraying. I heat the lacquer in my HVLP turbine unit cup with a silicon heating blanket that is glued around the cup and wired through a rheostat housed in an explosion-proof housing attached to the wall of the spray booth. I regulate the temp to 130 degrees F.
My spraying schedule varies with what I may have going on at the time, but I like to wait at least 1 hour between coats. I never spray more than 4 coats a day, and I feel it is totally unneccesary to sand between coats for adhesion. After 6 coats I will knock it back with 220. At this point, on open grained woods ,I will usually go 3 more coats. If I am level I will spray 2 more and let it rest for a month.

A typical schedule for me would be as follows:


Day 1
1 coat vinyl washcoat
If first coat of lacquer is to be applied more than 8 hours after the vinyl washcoat I scuff it with a grey scotchbrite pad first.
3 coats lacquer at least 1 hour apart

Day 2
3 coats lacquer at least 1 hour apart

Day 3
Sand back with 220 RO first thing in AM.

Day 4
3 coats lacquer at least 1 hour apart

Day 5
Sand back with 220 RO first thing in AM. Everything should be level at this point. (no pores, etc.)
Spray 1 or 2 final coats to melt in the 220 scratches.
Hang for 1 month

I average about a quart of lacquer per guitar.

That is how I skin that cat. I think we all strive for a balance between getting enough finish on the instrument that we don't sand of buff through while keeping it at a minimum so as not to kill tone. Not to mention the waste of using more than is required and other problems associated with a thick finish. There are so many variables in our equipment and application/sanding procedures that it comes down to each individual luthier developing his/her own own schedule and then modifying it as they gain experience with their own method. Trust me. You will sand/buff through. But you will get a better feel of what you are doing each time.

I hope this helps

Kent Schoonover
WWW.schoonoverresophonicguitars.com

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Kent Schoonover

WWW.schoonoverresophonicguitars.com

Hesh - just got to looking at the stewmac document now. I will adjust my process to fit in with this. One of the things I found helpful in its finishing section is not to try and get rid of all the shiny bits and hollows in the early stages. Because I have never had anyone show me what to do, I have probably been too heavy handed in the early stages of levelling.

Frank

If there are any other australians interested in this, it looks like Optigen in South Australia have this on their product list.
http://www.optigen.com.au/contact.html
I will add this to my list of things to try one day!! It's a long list.Thanks.

At my rate, I am doing double that volume, when I should be using less!!

Obviously, I am applying it too heavily in response to my bad experience on the previous guitar.

The variety of approaches used by the guitar building world in finishing, even for the same finishing product eg nitro, is pretty overwhelming!!

..ok, and that's without any thinner.
At my current rate of application, I am using about 1 quart of thinned (2:1) nitro.

So overall, the impression I am getting is that, while I might be going a little heavy, I am in the ball park.
Thanks for your other comments/suggestions - very helpful.
Frnak