Harmony Production Adhesives

The Harmony Guitar Company used at least five adhesives during the run of Sovereign guitar manufacturing. This was from late 1950’s to early 1970’s. Harmony changed manufacturing procedures very little during those years. Those adhesives are hot hide, PVA, and red glue and a solvent based adhesive.

Red glue bonds the liner blocks to the sides, top, and back. The neck block and tail block are glued to the sides with this adhesive. Also, they glued little 5/8 inch wide stick braces to the sides. Approximately 50% of the time, red glue bonds the braces to the top. Red glue bonds the back braces in one half of the cases.

I call this "red glue" because I have no idea what this adhesive is made of. It may be partly hide glue. Red glue is tough stuff. When dried it is very brittle. It is very difficult to soften with water, PVA glue remover, steam, paint stripper, alcohol, and lacquer thinner though it will soak loose in hot water after 15-20 minutes. Not that I recommend soaking a guitar in hot water. Red glue is very long lived. Sovereign guitars made in the 50’s are just as good as new. So, this is my plea for information on this adhesive. As a long time stick and tissue model builder and production wood worker, I have never seen this for sale anywhere.

Harmony used hot hide glue in four places: 1) neck to body dovetail joint 2) bridge to top 3) gear head wings to the gear head, 4) Fret board to neck. In newer Sovereigns, there is a 1/4 inch maple dowel glued into the heel perpendicular to the fret board. I think they used hide glue, though I am not sure if this is true in all cases.

After examining hundreds of neck to body joints, I can state with great confidence that Harmony employees used a paint brush to slather hot hide glue into the dovetail cavity. In every case, there is way too much glue in places where it is not needed and not enough where it is needed. In most cases, the hide glue was applied to the end of the neck, which is the flat end of the dovetail. In many cases, there is very little or almost no hide glue on the slanted sides of the dove tail where it is needed. This is why I say they used a paint brush. It would be very difficult to apply glue with a brush to the 3 inch by 1/2 inch sides of the dovetail without getting glue on the finished sides of the neck heel. Therefore, seems to me they took the least troublesome path to gluing the neck on. Also, I think the hide glue was cold. On some Sovereigns the "hot" hide glue cooled before the neck was attached. We see glue stuck to the sides of the socket (i.e. on the body) but none adhered to the neck heel. Possibly these guitars were assembled at start of day, or when the glue pot was not yet at full temperature.

A factor contributing to loose OEM neck joints is a poorly machined joint. Some fit better than others. By comparison, when you steam a vintage Gibson J45/LG0/L00 neck apart, the joint is perfect. The Gibson dovetail joint is so tight that it is very difficult to get the steam into the joint. And steam wants to flow everywhere. In many Sovereigns, if you clean out all glue from the dovetail joint, the resulting joint is very sloppy compared to a Martin or Gibson joint. You would think someone in management would have noticed this and fixed the problem. But no, they made thousands of otherwise excellent guitars with poorly fitting neck to body joints. Harmony manufacturing procedures did not change from the late 50’s to 1970. That is quite a run of poor quality control standards. What on earth were they thinking? Possibly this is why Harmony Sovereigns cost around $85 in the day, and Martin D-18 cost $500-600 and this is likely why Martin is still in business and Harmony is not.

Anyway, rest assured the guitar you receive from moonlightluthiers will have a completely corrected neck to body joint.

To me, the most interesting adhesive used by Harmony was PVA (Poly Vinyl Acetate). This was the earliest form of PVA. It is similar to Elmer’s white glue as is used in elementary schools these days. I don’t think Titebond glues existed when Harmony started using white PVA. They used PVA in the later years of Sovereign production to adhere braces and bridges to the top planks. Oddly, we don’t see many instances of top braces coming loose when adhered with PVA. I say "oddly" because it sure is easy to pull these braces loose from the top. On some guitars I can pull them out with bare hands.

In some cases, they used PVA to adhere the bridge to the top. Many of these bridges are coming loose. That is because those early PVA formulations were not strong enough for such a high tension application. (Hot hide glue is much better.) Furthermore, PVA prefers fresh cut or scrapped wood. I suspect that Harmony stacked hundreds of ready made tops and bridges on shelves somewhere. Months after these parts were prepared, they were glued together on the assembly line. PVA likes fresh cut smooth, clean surfaces. This is most probably why these bridges are now coming loose or lifting.

They often use PVA to adhere the braces to the back.

I think they used PVA in preference to hot hide glue because it dries much faster, thereby shortening production time. Time is money in the guitar world.

I am at a loss as to what was used to bind plastic bindings and the white plastic heel cap to the guitar woods. My guess is they used something like Duco or other solvent based adhesive. The use of solvent based glues raises an assembly line question: how carefully did they ventilate the areas where solvents were used? Lacquer was bad enough, but Duco and similar are seriously bad to breathe. I wonder how many employees went home with raging headaches each day, not to mention brain damage from inhaling the fumes.

There is one more adhesive used by Harmony. They used some sort of rubber or latex based adhesive to attach the pick guard. This adhesive is now failing at nearly 100 percent.

I hope the foregoing explains why we say all original condition Harmony Sovereign guitars need a neck reset at the very least. And conversion to X-bracing makes a Sovereign a far better guitar.


©2017 D.R. Hanna