While researching the A-bracing used on Ovation Legend and Custom Legend guitars in preparation for my next restoration project, I was looking on the Ovation Tribute site for old brochures. I happened upon a couple of documents that describe how Ovation attempted to replicated the sound of '50-year-old' guitars.

The first item I ran across was the brochure from 1974. (See: 1974 Ovation Custom Legend US Info Sheet)

It had the text, "Today, everyone is talking about 50-year-old guitars and tops that are thin and flexible. Well, for the last six years we have been working on building a guitar that would have the same sounds as a 50-year-old guitar, and we did it by developing a new top-bracing design that has never been used before. Together with this, we have pre-selected Sitka spruce tops that have a specific deflection range."

Boy, does that sound familiar! What is old is new again.

Deflection testing is nothing new in luthery. A lot of luthiers use top-wood deflection testing to determine which wood will produce the acoustic response they're looking for in their latest project. But, attempting to reproduce the sound of 50-year-old guitars was very cutting-edge.

So, I started looking at the Ovation Tribute site's historical documents and I found the following document concerning the treatment of top wood to replicate the response of the tops found on "50-year-old" wood. See: Ovation 1537 Super Legend Doc #02 (1980)

What this document shows is that, in 1980, Charlie was attempting to re-create the sound of old guitar on newly constructed guitars using chemicals to crystallize the wood fibers of the top wood. (glacial acetic acid & calcium acetate)

A lot of people have stated that the 1537 Elite is one of the best-sounding guitars ever produced by Ovation. What these documents show is that this guitar was not a serediputous combination of the quintaid bracing and wood top, but a methodical effort to create the best-sounding guitar using the technicology available at the time.

He was, in 198?, attempting to accomplish via chemistry, what has been realized in the 21st Century through torrefaction. (See: Ovation 1537 Super Legend Doc #09 (198?)'

Here are the steps:

1) Soak the wood at 20% Pota??? dioxide.
2) Then, soak calcium acetate & acetate acid PH 5 (possibly calcium caborate [sic])
3) fourced at 200F and Vacuum
4) [graphic symbol] about a weak [sic]

What do we want

a) appearance
b) mechancial

Torrefaction is able to re-create the mechanical properties of '50-year-old' wood by crystallizing the wood fibers by putting the tone wood into a autoclave which provides both high temperatures and low pressures.

These documents show that Charlie was on the right track and was 40 years ahead of his time.

Thanks, guys.

Further careful reading of the last link and a little searching online revealed the basic process.

1) Soak the wood at 20% Potassium Hydroxide. (KOH)
2) Then, soak calcium acetate & acetate acid PH 5 (possibly calcium carbonate)
3) fourced at 200F and Vacuum

Basically. the process used the KOH as a base (alkaline) to break down the wood fibers. (KOH is hydroscopic)
Next the, calcium acetate and acetate acid neutralize the KOH to stop the aging process.
Last, the wood is dried in a flat condition to keep from warping.

WRT whether the aging process produced the desired results, I would hazard a guess that it did not. The above documents were dated around 1980. A later (hand-written document) dated early 1982 showing the configuration of the 1537 asked for non-treated tops. (See: Ovation "Super Legend" Elite 1537 Document #03)

This could also be an economic decision as one of the documents noted the increased cost of the chemicals with the price of calcium acetate alone being 600% more expensive in 1980 vs. 1974.

Beal would be the one to know whether the process produced the desired results and for how long it was used in production, if at all.