The End of the Nitrocellulose Lacquer Era

The End of the Nitrocellulose Lacquer Era

by

Brian Howard Luthier

   Nitrocellulose lacquer (NL) was first used on guitars in the early 1920's. In recent years it has seemed to reach mythical status as a magic sauce that will instantly provide tone. And of course that means anything else is not as good and then obviously must kill tone...... Of course this is not true! In fact a lot of what you may have heard or been told in regards to NL simply isn't true either. So before we talk about why traditional NL is no longer really a viable option for fine guitars let's bust a few myths.

  First up is that NL is thinner than other finishes and doesn't choke the vibrations of the instrument as much. Typically not so...... in fact those cherished Gibson bursts are some thick finishes! I have seen them as thick as 17 mils from the factory, no overspray!! In fact the excess thickness is what leads to all the surface checking with age and is why some have checked more easily than others. Factories applied the NL quite liberally as the material is noted for it's ability to build thickness. This was to ensure that when the level sanding and buffing necessary to make a mirror finish was done they would not cut through the finish. This concern, the extra build necessary to buff out to a perfect surface is rather unique to musical instruments in general. NL was chosen largely because it worked very well in this system. If you actually want thin finishes however, then you want a modern finish. Most modern polymer finishes must have final film thicknesses under 5 mils. For comparison NL has a MINIMUM film build of 3 mils.....

  Myth 2, NL sounds better.... I have heard many supposed reasons for this one. That it is more/less flexible. I have heard both. But a study by Roger Simonoff showed that this is entirely dependent of final film thickness.Up to a certain point it added stiffness and then quickly became more flexible at about 7 mils. But even beyond the fact that thickness is tied to flexibility we are left with a basic problem with this claim. What does it mean " sounds better"?  That is a matter of opinion and taste and as such cannot be quantified scientifically or tested. I have done blind tests with players and listeners which never produced anyone who could pick out the NL guitar from a lineup sonically. But of course that in itself is highly unscientific as we cannot swap the finish on the exact same guitar so many other factors can influence this. But I sincerely believe that whatever you may be hearing is likely not the difference in atomic structure of the thin plastic coating on the surface.

  Myth 3, NL is a natural product and is somehow superior because of this. Without even touching the natural is better debate I will shut this one right down. The source may be a natural product like wood or cotton but the resin itself is a crude thermoplastic. In fact it was the very first thermoplastic compound and ushered in the modern age of chemistry..... so sorry but absolutely not a natural product at all. Varnish and shellac are natural and NL was a vast improvement over those. And today there are materials which are far superior to NL.

  But lacquer was good enough for all those years, right? well was it? Major makers like Rickenbacker have been using a modern poly known as conversion Varnish since the early 1960's. Fender started prepping all there bodies by dipping them in polyester resin in the early 60's as well. By the 70's more guitars, especially lower price ones started having poly finishes....why? Labor! While NL material was cheap it generally requires more labor to apply (3X-4X more!) than a  modern coating. But guitarists are known to be willing to pay a premium for things that improve the instrument is some way. So that brings the debate back to is it a better finish for a guitar?

  Ounce upon a time, Maybe. Today? No. Why is that? because the product as it existed 100 years ago isn't being made today. The product as it existed 30 years ago (which was significantly different from the original formulas...) doesn't exist anymore either. In fact even 10 years ago the material was better...... Why? Because we have discovered that lot's of the chemicals involved with this process are not very good for us or the planet at large. The first to go were the VOC's, a term you may have heard but do you know what that means to us and NL?

  Volatile Organic Compounds is a group of chemicals that have a high vapor pressure at room temperatures and thus have low boiling points. Meaning they evaporate pretty fast. These are important in an air dry finish like NL because we need a transport vehicle to carry the resin that will evaporate and let the coating form that is also strong enough to keep the resin dissolved. Fast, aggressive solvents allowed this to be a fairly fast process. When they were removed the process slowed drastically. The 2 weeks from last coat to buff-out became 4. That was 25+ years ago. Next came restrictions on HAP's which you may not have heard  of. They are  Hazardous Air Pollutants  and are linked to health and cancer concerns. This reduced farther  the available solvents to transport NL coatings.... Right now the solvents used are so slow to finally evaporate from the coating that 6+ weeks is the norm from spray to buff. That's a long time to have something drying in your shop.......

  This change in solvents has necessitated changes in the chemistry of the resin as well.... You see NL is much more than just nitrocellulose plastic. In fact only about 20% of the resin content in a modern NL finish is actual nitrocellulose. You need at least one stabilizing agent, typically a fatty acid. originally Camphor was the oil of choice but soon cod or castor oils were added to improve stability. without these the NL would simply check and flake off, it would be very brittle. Changes in the acid used have big effects on the coating. All modern formulas I am aware of use Soy oil as a modifier which seems to produce a much softer coating. Then there are the other modifying resins that are added to help improve UV exposure stability, reduce cold checking etc... These actually can be as much or more of the actual content in modern NL as the nitrocelluloid itself. So in essence what we are spraying today is nothing like those historic finishes you may be yearning for.... It is much softer and less durable and needs to be applied thicker. 

  There are ways around some of this. Dry times and film hardness can be drastically improved by catalyzing the chemical process and making the drying or "curing" a chemical reaction instead of the typical air dry of traditional NL. In fact I suspect Martin has been using this approach for there NL finishes for several decades. But this requires different resins and filler compounds known as "cross-linkers" and in the end what you really have is a hybrid coating somewhere between NL and poly. And if you are willing to go that far in deviating from the magic of NL why not just join the modern age and use a truly state of the art finish?

  In fact the sun is setting fast on most solvent borne systems.... Conversion Varnish, 2 part urethanes and the like are all going to going away in the not to distant future. This is for several reasons not the least of which are the environment and health. This is going to leave two basic types of coatings. Water based which could be air dry or catalyzed and 100% solids solventless systems. Water poses problems as no finish resin worth using will readily dissolve in it requiring extra chemistry which always alters clarity of the finished film in some respect. And makes the manufacturing process a little more dirty for us and the planet as well. 

The future is in the solventless systems. Especially the UV cured types. Though these finishes suffer a bit of a bad reputation in the guitar world because the minute you mention them everyone thinks of those cheap guitars with finishes 1/8" thick. But as I pointed out earlier, a lot of those old NL finishes from the glory days are actually quite thick too..... But they do not need to be. The key here is that while they can be applied at almost limitless thickness, they can also be applied incredibly thin and function at that thickness very well. Much like the original NL. They also tend to exhibit no yellowing so that blue guitar will not turn green in a few years and that nice red burst will not disappear as it ages. Big plusses in my book.

  Now I know someone out there is saying " yeah, but NL is easier to repair". Well my first response is it is easier to damage..... But is it easier to repair? Most who tell you this have never done much of this type thing, I have. And I'll tell you that is not the case. Most shops are using CA (superglue) to fix all finishes these days. Simply because they don't have a spot for you guitar to sit and have those drop fills dry for several weeks.  And once you do any repair with UV cured materials and see how quick, easy and seamless looking it is..... well it's all you'll want to deal with.

  So just as we have had to accept the fact that Brazilian Rosewood  and Ivory are no longer real options for our instruments we must too accept the passing of the age of Nitrocellulose..... And as with those other examples this is not a bad thing. There will still be original pieces out there for the collector and the player will appreciate the more modern offerings as they hold up better providing better protection of the investment in the instrument. Because let's not loose sight of one basic fact here. The finish was never intended to be part of the production of sound. It's sole function and the only reason it was ever applied was to protect the instrument from the elements and wear. If it was a tone thing every acoustic guitar ever made would be finished completely inside and out..... but they are not are they?  Hope this helps you understand a bit more  about guitar finishes.

Brian Howard Luthier