The purpose of this article is to show the difference between Hide (Protein) vs. PVA Glue in Guitar Construction.
Hide/protein glues have been the standard for guitar and stringed instrument makers for centuries. It was not until the mid to late 20th century did white PVA (Polyvinyl Acetate) wood glues take over in popularity. This was due to their ease of use, long shelf life, good tonality, and over all strength.
Many fine guitar builders still use hide/protein glues for their tonal and structural characteristics. Such famed makers such as Bourgeois, Collings, Gibson, Martin, Taylor, and others offer hide/protein glues as either a standard or a specialty option.
Hot hide/protein glue pros:
- Crystallizes producing prime tonal conveyance.
- “Melts” into existing glue residue on repairs producing a strong bond between old and new.
- Thin consistency which allows it to easily flow into hard to reach places producing a tight bond.
- Easy to remove for repairs, yet strong.
- Sustainable and non-toxic.
Hot Hide/Protein Glue Cons:
- Requires careful preparation for use.
- Does not have long shelf life once constituted.
- Dries quick allowing no room for errors.
PVA/White Glue Advantages:
- Thicker and slower drying making for easier application and more working time.
- Ready to use right out of the bottle. No heating or prep required.
- Strong & Durable.
- Good tonal conveyance.
- Sustainable and non-toxic.
PVA/White Glue Cons:
- Harder to remove for repairs.
- Has very subtle affect on tone to a discerning ear.
How the hide/protein glue is applied:
To demonstrate I have included pictures of a vintage 1960’s Gibson J-45 bridge reset recently done at our shop. This model had a rout for an adjustable ceramic saddle so there was little bridge to top contact and thereby poor glue adhesion. The bolt on bridge works in unison with the glue, but the bolts don’t help much when they work their way loose over 40 years!
The glue is processed at the factory to thin dry flakes, or a granular form that resembles unbleached sugar. In this form it has an indefinite shelf life. To constitute, the dry form is put in cold water at about a ratio 1 part glue to 3 parts water. Afterwords it is left to set for a couple hours. In this time the glue and water will blend to a tapioca/gelatin like consistency.
The glue is then heated in a double boiler or glue pot to 130F-140F. If allowed to scorch or overheat the glue structure will be ruined. To prevent this many luthiers use a specialized glue pot that regulates the heat to avoid damaging the glue. When heated it is slightly thicker then water and applied with an artists brush. The constituted glue can only be reheated and used for about a week or two before it goes stale.
Even though an instrument can be repaired well using alternative glues, we at Randee’s Music do not compromise for simplicity or ease of use. We strive keep the structural integrity of our customer’s guitars as they were designed and built to be.
Look for further posts from the workbench on the structural and tonal aspects of guitar construction.