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I've tried every brand of nitro I could get my hands on over the past 50 or so years and the only ones I really liked were Guardian and Valspar. Now I can't buy either one since Guardian was bought out and eliminated and Valspar requires a 240 mile round trip drive to purchase.

I'm considering switching to polyester. Am I crazy or is this the right way to go. I'm willing to spend some money to simplify finishing and get away from the 5-6 weeks of waiting for the lousy modern (ruined) nitro to harden enough to polish.

Any advice would be greatly appreciated. We build flamenco and classic guitars exclusively.

Not interested in French Polish? I use Royal Lac to good results. Applied as normal French Polish, becomes impervious to alcohol an mildly scratch resistant in about 30 days.


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I use both shellac and nitro. Both have their place. I know your problems re: the nitro, even here in Aus. If you're happy with the Valspar, if it were me I'd order plenty and take the 240 mile drive. A lot, lot quicker, cheaper and lower risk than trialing a bunch of alternatives.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Yep, all modern nitro is crap!!!! It's the lousy base stock and all the modifiers in it.

I am discontinuing my nitro on new work and only using it on restorations at this point......Since switching to UV pore fills last year I am currently in the process of running out test panels on 16 different species of wood with an all uv cured polyester finish. I think this is the future....

I will continue to offer a conversion varnish as I love it for acoustics but will likely be replacing all my nitro and 2K with the UV poly.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Does anyone know why the formulas for Nitro have changed over the years?

Pressure from environmentalists groups over VOC's.

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"Act your age, not your shoe size" - Prince

If you are going to "try out" polyester I would suggest you buy a cheap jamb gun (you can dunk in a can filled with acetone) before you commit any expensive equipment to it.

What are the symptoms if this suspect nitro?

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Pat

While the loss of certain solvents due to clean air standards is a part of it the real reason is technology moves on. Nitrocellulose is 100+ year old tech. Might as well be asking why airplanes are not made of canvas anymore....

Original formulations had problems like crazing so new modifiers were developed and cross linkeres added. Finish yellowing is considered bad by everyone but guitar nerds so modifiers have been selected over time to minimize this. Also I suspect here in the modern world some other factors may be at play. Nitrocellulose base stock with nitrate levels high enough to make it suitable for lacquer finishes is almost a high explosive, a little more nitrate and you have smokeless powder.....So i believe some things have been added in the past 20 years to make it very difficult to remove the stabilizing plasticizer and increase nitrate content......

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

It takes forever to cure/harden. The brand I just tried is approaching 6 weeks since the last coat and it's still a little too soft to polish properly. I used to be able to polish after a couple weeks. We usually build 4-5 guitars at a time and the shop gets overloaded with guitars waiting for polishing. Customers aren't happy about the extended wait either.

We don't use much lacquer - we're still spraying Mcfadden, so I don't have experience with some of the other currently available things.

I understand Cardinal nitrocellulose lacquer is quite similar - you can get it from LMI.

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Cheers,

Frank Ford

FRETS.COM
HomeShopTech
FRETS.NET

So it sounds to me like they have addressed problem issues, over the years, with the finish. Isn't that a good thing? Doesn't this only make for a better product? I'm no expert. I've likely only sprayed about 200 gallons for various uses, but it seems to work pretty well. And you could darn near apply it with a stucco brush. Pretty user friendly..... other than the stink.

I tried that on the previous batch of guitars. Same result as everything else...takes way too long to cure, it's also ridiculously expensive.

I recently started using Simtec poly. I did some radical stress testing on their products before applying on a guitar and I'm impressed. Originally, I was going to go with polyester (catalyzed not UV). But after working with the stuff, I didn't much care for it. I talked with Simtec, and they said their polyurethane is just as hard. It sprays easily, buffs nicely, and cures in 30 hours. I'm very happy with my results- in both gloss and satin.

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ELEVATE || Next Level Lutherie
http://elevatelutherie.com
&
http://ensorguitars.com

Isn't Cardinal the stuff that's supposed to dry faster than regular nitro??

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Pat

In a word, yes...but. Trying not to denigrate products, it's always possible that I'm doing something wrong although I've been doing this for over 50 years and haven't changed my methods.

I went to their web page and couldn't find any polyurethane listed (all polyester). Could you give a little more information on the product you're using? What you're using sounds like exactly what I'm looking for.

Their urethane is actually sold as their sealer but can be used as a topcoat as well. It's the 58x1, 58x2. It's mixed 1:1, has an 8-9 hour pot life and can be sprayed with 45 minutes between coats. I suspect you could spray it sooner if your shop is dry and warm. Those numbers are what Simtec recommends.

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ELEVATE || Next Level Lutherie
http://elevatelutherie.com
&
http://ensorguitars.com

I am very interested in this thread. I've struggled plenty with nitro finish. Spraying is easy. But just how long do I wait for the final smoothing and buffing? And how do I go about that without introducing those very deep scratches that won't come out without a burn through?
I've been using Mohawks musical instrument nitro for the last eight builds. A cure time of ten days with constant air circulation at room temp. I run a small air purifier fan close by. Starting with Mirka Abralon 800 grit. On a Festool 3/64" orbit at its lowest speed. Work up through to 4000. These are used with just enough water to produce a light slurry. Then on to buffing. This has worked well for me on the last two builds. Keep the area very clean. Ask me how I know.
I can't speak for other nitro brands. I've stuck it out with Mohawk as I still have a few gallons left. (Waste not want not ya know). I'm not a nitro purist regarding acoustic qualities but I do like the repairable qualities. I do spray on as thin as I dare though.
Don't know if this will help especially since the OP has been working with nitro for 45 years longer than I.
But this formula works for me. Cheers.

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"It is easier to fool a man, than it is to convince him that he has been fooled"
Mark Twain

I didn't mention that I level between the build up spray sessions with either Mirka micro star or wet dry 320 paper which has soaked for at least a day.


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"It is easier to fool a man, than it is to convince him that he has been fooled"
Mark Twain

These are my most recent results using Cardinal, 800 grit Granat paper, and the buffing schedule Chris Ensor shared last summer.

I buffed the lacquer seven days after spraying. I sanded the last set of coats that morning with Festool Granat 800 on a Festool ETS-125. The sander was on the highest speed and I used soapy water (dish soap) with the paper. One thing I've noticed with Cardinal is that the sanding dust gums up and sticks to the the finish when you sand it unless you're wet sanding. When it does, you have to scrape it off with a razor blade or risk it pulling out a chunk of the finish underneath. It's really annoying, but wet sanding completely takes care of it for me.

Like I mentioned, I followed the buffing schedule Chris Ensor shared last summer with great (IMO) results. The finish was completely scratch free. I used Menzerna 204 on canton flannel wheels from Caswell Plating, followed by Menzerna P175 on 60/60 cotton wheels from Jescar.

This schedule worked really well for me. I'm really happy with the results.

Perhaps unconventional, but in my high gloss finish process I use nothing more course than 600 grit for leveling. Quantum improvement in results when using water borne and yes nitro too. This was a suggestion from a General Motors paint shop tech. And yes it takes a little more time.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I have been using 600 grit as well and I think I get a really nice finish. I don't understand why you would sand out to anything finer than that.

I use the brown Menzerna and the white and it seems to make a "scratchless" finish.

The "trick" I have found is that when you reflect a light on the finish if you see any scratches (from the sanding) you need to go back to the courser buff and polish them out

I use Behlens instrument lacquer and let it dry for a minimum of 2 weeks.

You can see my finish on the last guitar I posted-" Brad Goodman J-45"

600 wet here too but by hand.

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Steve Smith
"Music is what feelings sound like"

I've been buffing with liquids as I don't have a buffing setup large enough to handle the 16 - 18" wheels. Maybe in the future.
I'm curious how long does it take to buff out from the 600 grit sanding on a wheel? If I sand to 2000 I will spend an hour buffing more or less.

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"It is easier to fool a man, than it is to convince him that he has been fooled"
Mark Twain