MIMF

Any consensus on the best way of attaching a pick guard to an acoustic guitar or a flamenco for that matter? Different methods for different finishes. I can imagine repair shops get ones in which were stuck on with CA. I assume the wooden one on old flamenco guitars were put on with hhg. What method is going to cause the least damage to the finish over the years and then come off cleanly if needed. Assume that the finish is either nitro or shellac.

I found a couple of threads about removing them (e.g. repairing cracks under a shrunken Martin pick guard), but nothing about sticking them on in the first place. The only pick guards I have done were on two StewMac kits I build years ago. I think they were self adhesive.

Nothing urgent. Curiosity.

Self stick pickguards over finish. Pressure Sensitive Adhesives, transfer adhesives, etc.

I've done 3 Martin pickguard replacements under warranty in the last week. Each case they were originally glued down to the wood and finished over, and in each case the plastic shrunk over the decades, pulling the wood with it and developing cracks.

We remove the pickguard, flatten the cupping, glue the cracks, and then finish the bare wood and install a self stick pickguard. This way, if the new pickguard shrinks over the next 40 years it will slide creep and side over the finish, and if needed can be easily removed and replaced again without any damage.

As David mentioned, the transfer adhesive mounted guards over finish are the industry standard. Martin does some lacquer-over stuff on Authentics, but the early ones are showing enough shrinkage of the cellulose nitrate layer of the laminate that they show a line at the edge that is unsightly...another reason to stick with over-finish guards.

We use both single layer adhesive and laminate transfer films, but prefer 3M 468MP for tinted or opaque guards...available on Ebay in small quantity and reasonable cost due to the scrap generated by sign makers...I buy enough material for 30-40 guards for under $1 per guard...a roll of the stuff can run a few hundred, but that's enough sticky stuff to do hundreds of instruments. Don't be afraid of picking up guard material in larger sheets and applying the adhesive after shaping...this also makes wooden guards and non-traditional materials like laminated shell a practical alternative. For lacquer, poly, or varnish (including wiping varnishes like TruOil), wet application works best; for shellac, use a dry application.


The usual process for fab and wet application in my shop is as follows:

1. Make a paper or mylar template of the desired guard shape and trim the pick guard stock as required. For my operation, I make a routing template out of 1/2" MDF, then use a top bearing pattern router bit to trim the slightly oversized blank......cut to within 1/8" on the rough trim to avoid the bit grabbing things, etc. The extra ten minutes it takes to make up a template pays off when it can be reused for same model/same year jobs. We save each template, and usually see good consistency between guard patterns on are model and year of guitar. For a one-off, it's likely more efficient to shape by hand with scissors, file, sanding drum in drill press, etc. Don't be reluctant to improve the templates used on factory guitars when replacing one of those cheesy pizza guard on a Martin, etc.

2. Bevel the edges with a chamfering bit or razor blade scraper, wet sand to P800 (for cellulose nitrate, cellulose acetate, or the hard black vinyl that Martin and a few other vendors sell), then buff.

3. Apply the adhesive and trim (3M 468 has a thin scrim of mylar between two layers of adhesive, so use a fresh razor blade to trim closely...don't leave any excess.

4. Clean and if necessary, buff the area the guard will be applied...no dust, dirt, etc., and no wax, stray polish, etc.

5. Position the guard, use a piece low-tack blue tape to function as a hinge, flip up the guard, mist area with distilled water and dish soap mix (2 drops of Dawn in a quart of water works), then peel backing and - from center to edges, use a wet paper towel as squeegee to push any air or water out from under guard (be careful to avoid too much pressure - supporting the area from underneath with a free hand is a good idea.

6. Any residual water/soap mix will clear in a week or two, but try to get it all out with the wet squeegee approach.

I'm sure David has a few other tricks to impart - I've had a couple of his Martin guard redo's in over the last few years, and they are very clean. Latest is a minty black guard late 1967 000-18 with V100 tuners intact, David - ring a bell?

David, Todd.
Thanks for those great answers.