French Polish vs. Nitro

[Malcolm Kindnes]

I have a couple of nitro finished guitars, one with a French polished top and a classical with an oil finish. The French polish is beautiful and I would say, if you're careful it shouldn't give you any more trouble than the nitro.
The nicest finish I've come across recently was on a friends Goodall, I don't know what it is but it feels and looks gorgeous.
The French polish is usually quite a significant upcharge, it is very labour intensive.

[gitarro]

I have a guitar that's more than a decade old with a top of French polish and it seems to be quite hardy. On the other hand I had a guitar wifh French polish that was new and it was much more fragile. So maybe French polish becomes harder and much more stable the older it is.

[Wade Hampton]

Originally Posted by gitarro

I have a guitar that's more than a decade old with a top of French polish and it seems to be quite hardy. On the other hand I had a guitar wifh French polish that was new and it was much more fragile. So maybe French polish becomes harder and much more stable the older it is.

The other possibility that suggests itself is that the French polish finish on your current instrument was applied by someone who was better at that process than the person who did the first one. The quality of French polish finishes are definitely affected by the skill of the person doing the work.


whm

[zhunter]

Originally Posted by gitarro

I have a guitar that's more than a decade old with a top of French polish and it seems to be quite hardy. On the other hand I had a guitar wifh French polish that was new and it was much more fragile. So maybe French polish becomes harder and much more stable the older it is.

Yes it can take months for French polish to fully cure and fully harden. Hardy? All I can say is that is highly relative. Fully cured, genuine French polished finishes will remain more fragile than cured nitro.

hunter

[zhunter]

Originally Posted by Wade Hampton

The other possibility that suggests itself is that the French polish finish on your current instrument was applied by someone who was better at that process than the person who did the first one. The quality of French polish finishes are definitely affected by the skill of the person doing the work.


whm

Overall quality maybe, but hardness and durability? Largely a function of materials used.

hunter

[Alan Carruth]

Gitarro is right: FP does become harder and more chemical resistant with age. After about 75 years it's impervious to just about everything. Nitro, OTOH, ages badly.

Classical makers like FP for two reasons: tradition, and the fact that it goes on so thin. The more mass you add to the soundboard the less responsive the guitar, and FP is about the thinnest finish that provides good protection. Since it was also the most common finish on Spanish instruments up until the 60s or even later it was always possible to find somebody who could re-polish the guitar if it got dinged or worn.

In terms of the hardness of the film, at a given thickness shellac only gives up about 1/3 of the hardness of nitro. The problems with wear and dings have more to do with the thinner film, and, of course, the fact that shellac dissolves in more common solvents. Aside from alcohol, it dissolves in alkaline water solutions, which seems to equate with 'sweat' for some folks. You're far less likely to run into the solvents for nitro in your daily rounds: if somebody puts MEK in your drink you've got bigger problems than just spilling it on your guitar.

Shellac actually has the advantage over nitro in terms of toughness: it's far less chippy at a given thickness, and tends to dent rather than scratch.

These days I tend to use an oil/resin varnish on the back, sides and neck, and FP on the top of Classical guitars I make. A good varnish will be tougher than nitro but nearly as hard, relatively chemically inert, and can go on almost as thin as FP. The inertness makes it a bit harder to touch up if it gets dinged. Varnish can be tricky to use, of course, but there are tricks in every trade.

Finally, in terms of health and safety, it's hard to beat FP: all of the ingredients are edible (in moderation!), provided you use pure grain alcohol as a thinner. Varnishes are probably not as safe, but the main environmental issue with most of them seems to be VOC. I've been brushing varnish for years in the shop and have not turned any funny colors yet. Nitro, by comparison, is a disaster. I've been told that the least toxic thing in lacquer thinner is toluene, and that's toxic at a concentration of 1/10 of what you can smell. It's also a fire hazard, if only because it's the little brother to a high explosive. Spraying it makes both the health and fire hazards that much greater, and then there's the VOC. At this point, having used nitro from time to time in the dissipated days of my mis-spent youth, I am now so sensitive that I can't even open a can. Having found something better, I don't want to anyway.

[Wade Hampton]

Hey, Al, please translate "MEK" and "VOC."

Thanks.


whm

[jaymarsch]

Originally Posted by Wade Hampton

Hey, Al, please translate "MEK" and "VOC."

Thanks.


whm

Methyl Ethyl Ketone and Volatile Organic Compounds.

Best,
Jayne

[jaymarsch]

Originally Posted by Alan Carruth

Gitarro is right: FP does become harder and more chemical resistant with age. After about 75 years it's impervious to just about everything. Nitro, OTOH, ages badly.

Classical makers like FP for two reasons: tradition, and the fact that it goes on so thin. The more mass you add to the soundboard the less responsive the guitar, and FP is about the thinnest finish that provides good protection. Since it was also the most common finish on Spanish instruments up until the 60s or even later it was always possible to find somebody who could re-polish the guitar if it got dinged or worn.

In terms of the hardness of the film, at a given thickness shellac only gives up about 1/3 of the hardness of nitro. The problems with wear and dings have more to do with the thinner film, and, of course, the fact that shellac dissolves in more common solvents. Aside from alcohol, it dissolves in alkaline water solutions, which seems to equate with 'sweat' for some folks. You're far less likely to run into the solvents for nitro in your daily rounds: if somebody puts MEK in your drink you've got bigger problems than just spilling it on your guitar.

Shellac actually has the advantage over nitro in terms of toughness: it's far less chippy at a given thickness, and tends to dent rather than scratch.

These days I tend to use an oil/resin varnish on the back, sides and neck, and FP on the top of Classical guitars I make. A good varnish will be tougher than nitro but nearly as hard, relatively chemically inert, and can go on almost as thin as FP. The inertness makes it a bit harder to touch up if it gets dinged. Varnish can be tricky to use, of course, but there are tricks in every trade.

Finally, in terms of health and safety, it's hard to beat FP: all of the ingredients are edible (in moderation!), provided you use pure grain alcohol as a thinner. Varnishes are probably not as safe, but the main environmental issue with most of them seems to be VOC. I've been brushing varnish for years in the shop and have not turned any funny colors yet. Nitro, by comparison, is a disaster. I've been told that the least toxic thing in lacquer thinner is toluene, and that's toxic at a concentration of 1/10 of what you can smell. It's also a fire hazard, if only because it's the little brother to a high explosive. Spraying it makes both the health and fire hazards that much greater, and then there's the VOC. At this point, having used nitro from time to time in the dissipated days of my mis-spent youth, I am now so sensitive that I can't even open a can. Having found something better, I don't want to anyway.

Thanks, Al. Since I have only owned a French polish guitar for about 7 years, I had no idea of how age affected it.

Best,
Jayne

[Wade Hampton]

After I asked for a translation, Jayne wrote:

Originally Posted by jaymarsch

Methyl Ethyl Ketone and Volatile Organic Compounds.

Mmmm....sounds yummy!

Thanks.


whm

[Rodger Knox]

I think Paul and Wade have pretty well covered everything, except that it takes FP a while to harden. For the first couple of months, it's reputation as fragile is probably deserved. But after a few years, it's nearly as hard as nitro.
edit: half a page of posts while I was typing, nevermind....

[Tico]

Obviously we shouldn't spill liquid onto our guitars.
But if we accidentally did, and of course cleaned it up ASAP ...

Which finish would do a better job of keeping the liquid from getting to the wood, FP or nitro?

I assume nitro, but perhaps I'm wrong.

[Rodger Knox]

For a newer finish, nitro for sure. After 20 years, almost all nitro shows a little crazing, and FP has hardened enough that it would take a while for alcohol to begin to dissolve the shellac.
Even fresh FP should withstand the alcohol content in normal drinks if blotted off within a few minutes.

[Alan Carruth]

OTOH, old, crazed nitro isn't much protection.

[Christopher Cozad]

Originally Posted by Alan Carruth

OTOH, old, crazed nitro isn't much protection.

Great point! Ages ago I had an old Guild jumbo with a completely shattered soundboard finish (one too many air cargo flights). Someone, trying to be helpful, had "polished" my guitar for me with a silicone-laden material that ran through 10,000 cracks and embedded itself fully into the Sitka top. I tried to refinish it...