"Pardon my typos. I've lost alot of brain cells in my day. Could it be the 'Nitro'.
The first Fender lap steel was finished in black enamel. When Doc Kauffman and Leo formed K&F guitars in 1945, their original instruments, including the amplifiers, were finished in a lead based, wrinkle coat enamel. A nice shade of Battleship Grey. That was the only color available. After expermenting with different woods other than pine for guitars, they began using nitrocellulose lacquer. They used what was available to the furniture trade at the time.
The original colors were blonde, sunburst, etc... just like your Grandmas coffee table.
Custom colors were introduced in 1955. Once again they were enamel. The same material they used in the auto industry. The enamel would not adhere to the stearate based nitocellulose sanding sealer. Acrylic lacquers were then developed by Dupont to be sprayed on material other than metal. "Duco colors". In order for the paint to adhere, Fender began using a Sherwin Williams product called Homoclad. It was a penetrating, heavy solid, oil based sealer used as a barrier coat to to provide better adhesion for their guitars with custom colors. It was applied by dipping the guitar bodies directly into a 55 gallon drum, filled with the product. ALL Fender guitars produced after 1955 used this product until 1967, when Fender began experimenting with polyesters an undercoat.
By 1968, virtually all Fender guitar products used polyester as an undercoat, including necks. It's a two part product using Methyl Ethyl Ketone(MEK) as a catalyst. The reason the face of the pegheads were not sealed with polyester, is because type 'C' decals (under the finish) would not adhere to the product. While it is true a few guitars may have squeaked by with homoclad, when homoclad wasn't available, they used a Fuller O'Brian product called Ful-O-Plast. PLASTIC!!! It's obvious to me that those necks or bodies were stragglers, having to be reworked for some reason or another and not shipped after the change.
I'd like to make one thing clear... ALL FENDER GUITARS PRODUCED AFTER 1968 HAD A POLYESTER UNDERCOAT WITH A LACQUER TOPCOAT!!! There is no specific ratio. Enough poly was, and is sprayed to properly fill the grain while preventig a burn through while sanding.
In 1983, Fender began using polyuerthane as a topcoat. It cured quicker. It had better clarity. It had more depth and gloss, and didn't melt when you accidently spilled 151 on it. Fender then discontinued the use of polyester on the necks. Polyurethane is a 2 part product using a catalyst.
Fender has continued to use polyester, polyurethane, nitro, homoclad, and Ful-O-Plast.
Nitro is not a superior finish. An electric guitar doesn't 'breathe' at 120 db.
My first year at Fender I personally painted approximately 46,000 guitars. I like polyester. I like Nitro colors too. But maybe I'll let the players that use poly (ester or urethane) speak for themselves...
Billy Gibbons, Geddy Lee, Alex Lifeson, Joe Perry, Jimi Hendrix, Eric Clapton, Roccco Prestia, Jimmie Vaughn, Nils Lofgren, Vince Gill, Chet Atkins, Tom Hamilton, Lenny Kravitz, Merle Haggard, Don Rich, Darryl Jones, Mike Stern, Larry Carlton, Peter Frampton, Sting, Marty Stuart, just to name a few. More are available upon request.
Hope this helps,
Mark K."
