Tech Talk on Glue…Trigger Warning…this is for lutherie geeks!

Glues I use in lutherie, where I use them, and a bit about why.

Hot Hide Glue

This is the traditional glue used for centuries, and it is still a favorite for many lutherie jobs. Hot hide glue may have tonal benefits largely because of how hard it cures, and because it pulls the glue joint together as it cures. It has better heat resistance than Titebond and other “carpenters’ glues” as per tests done by luthier Frank Ford. It has very low cold creep, and so a properly fitted joint will not move over time due to stress. It is only good for well fit joints. Hot hide glue joints are reversible with moist heat, and some grades can be shocked apart; both of these qualities make it a must for violin construction and repair. New glue reconstitutes old so it is good in repairs of older glue joints without the necessity of cleaning off all the old glue…an issue with carpenter’s glue. A major plus in production is that HHG sands to powder, and thus not loading up gunk on our wide belt sander belts when we use the glue for center seams on book matched guitar tops and backs. Also, when used in repairs, HHG can make a very strong and nearly invisible glue line; I’ve done major repairs where after finish touchup, I cannot see the glue line. Hot hide glue comes in a range of gram strengths, we generally use the 192. For a great treatise on HHG, see: http://www.frets.com/FretsPages/Luthier/Data/Materials/hideglue.html

Uses:
* Center seams for tops and backs
* Gluing braces to tops and backs
* Bridges on acoustic instruments
* Kerfing for acoustic guitars
* Tops to sides on acoustic guitars

Fish Glue

This is another traditional protein based glue but one which doesn’t need to be heated. The best fish glue is “isinglass” made from the air bladders of Russian sturgeon; it’s getting hard to find; Kremer Pigments is a source. It is good for most places you’d use HHG. Fish glue has a long “open time” making it easy to align joints and allowing plenty of clamping time, but it does take a long time to cure. Fish glue can also be made from other fish…cod was a major one, and it’s a favorite of some classical guitar builders like Jose Romanillos. If you remember Le Page’s glue with the funny bottle and rubber applicator top, you know fish glue!

Caveat: Fish glue is more hygroscopic than hot hide glue, and thus it is not good in high humidity conditions. The sturgeon isinglass is the most humidity-resistant type.

Uses:
• Pretty much any wood to wood glue joint in a guitar and anywhere you might use Hot Hide Glue

LMI “Luthier’s Glue” from Luthier’s Mercantile

This glue (I believe it to be a polyvinyl acetate..PVA) has the convenience of Franklin Titebond and other “carpenters’ glues”, yet cures much harder and seems to have some of the favorable qualities of hot hide glue. It is known for low “cold creep”, a possible real factor with regard to tone and the need for neck resets on acoustic guitars.

Uses:
* Peghead scarf joint
* Most assembly of semi-hollow guitar bodies in my shop
* Some less sonically important joints in acoustic instruments

WEST Epoxy

WEST epoxy was developed initially for the purpose of making cold molded yachts using the :Wood Epoxy Saturation Technique”. WEST epoxy cures hard and very clear; it’s great for bonding difficult to glue woods; does not introduce water into the glue line; joints can be taken apart with heat if need be. There are two versions of the hardener that we use…fast and slow, and there are a number of additives to alter the viscosity of the epoxy for use more as a putty, this being more useful in boat building. One of the great things about the WEST system is their metering pumps for the quart and gallon cans. One pump stroke of epoxy to one pump stroke of hardener.

Uses:
* Laminating necks
* Fingerboard to neck joints
* Laminating fancy wood skins and veneers to guitar bodies
* Gluing on “back strap overlays” on the back of pegheads
* Potting pickup coils in the shells

Smith & Co. CPES ( Clear Penetrating Epoxy Sealer )

Another great epoxy often used to stabilize woods like rosewood to prevent cracking. It’s nearly water thin and so it penetrates well into wood. Often used to stabilize rotting wood on boats or buildings.

Uses:
* Primer for wood finishing…pre-sealer
* Rot and spalting stabilizing
* Toughening wood

Franklin Polyurethane Glue

This is glue is catalyzed by moisture; for fast cure, it’s recommended that you mist dampen one side of the glue joint, but I generally do not use any water with it; we allow the ambient moisture content of the wood to do the job. With our semi-hollow Renaissance instruments it’s great for gluing the centerblocks onto cedar, spruce, or other wood tops as the glue line does not telegraph through to the top like it would with a water born glue. With peghead overlays, again, the lack of water makes for a stable layup without subsequent shrinkage as you’d get with the LMI white glue, fish glue, or HHG.

Uses:
* Center block to tops on semi hollow Renaissance guitars
* Laminating layered “skate boards” for “back strap” peghead overlays

Cyanoacrylate, aka CA or Superglue

Gear Up has a range of cyanoacrylate “super glues” and their “Glue Boost” is the best of all the accelerators to speed up cure. The glue also works well with baking soda as a temporary nut slot filler when the slots are too deep.

Uses, thin superglue:
* Gluing and stabilizing frets
* Inlay dots
* Some polyester finish repair. Gear Up’s “Fill and Finish” is formuated for this application
* Some binding work
* Some quick repairs

Uses, thick superglue:
* Inlay
* Some binding work
* Quick repairs
* Making jigs and fixtures
* Bonding carbon fiber to wood

Duco Cement

We just keep coming back to Duco for binding. We’ve tried the rest, Duco’s the best! If you built balsa or plastic models as a kid…or do now…you know Duco! Do not huff the product!

Uses:
* Binding (plastic/celluloid)
* Laminating celluloid

Melted Celluloid or ABS

You can make your own colored glue for celluloid or ABS bindings by melting down scraps of binding in acetone.

Uses:
* For dealing with gaps and joints in celluloid binding

5 thoughts on “Tech Talk on Glue…Trigger Warning…this is for lutherie geeks!

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