Official Luthiers Forum!

Paint is nitrocellulose.

Bind before or after painting? (taping is a pain)

Is there a glue for plastic binding that won't react with Nitro?

Mike

Bind first, then spray. Scrape the finish from the binding before adding clear.

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"Act your age, not your shoe size" - Prince

Hey there Chris. I tried that. Scraping not so much fun. Lead to minor scratches. Tried taping too. Somewhat better. Was hoping there was a glue better for this.

Fish glue?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use a sharp razor blade, Mike. You don't need a lot of the blade sticking out of your fingers to scrape off the finish. Do it in a smooth motion. I tried masking in the 70's. Made a ridge that I did NOT like, looked horrible.

Here is a quick tutorial from the great Tom Murphy!
https://www.youtube.com/watch?v=TNbsZsS ... el=StewMac

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"Act your age, not your shoe size" - Prince

I use CA to glue plastic bindings. Never had a problem with nitro reacting with the glue. If I do a burst I scrape the bindings before the final clear coats, as Chris mentioned.

By the way, Mike - I always used Duco Cement in the green & yellow tube for gluing binding. I suppose Titebond might work. CA should be good if used sparingly.

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"Act your age, not your shoe size" - Prince

wood glue doesn't hold any plastic

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Straight acetone works very well. Also, a solvent cement such as Duco, Welden #16, or stew macs stuff works.
I’ve never had any issues spraying nitro on it.
I mask and scrape the binding after color coat.

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wah
Wah-wah-wah-wah
Wah

I’m guessing this is a technique issue

Well...yeah. And practice makes perfect. You'll get the hang of it, Mike. I don't think any of us started out awesome.

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"Act your age, not your shoe size" - Prince

Binding is typically leveled by scraping it flush after installation. While it is possible to do this on a finished instrument, it is not recommended. As tedious as masking binding can be, it is far easier than the alternative.

Sent from my SM-G950U1 using Tapatalk

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John

Bind using UHU Hart glue, then paint/burst, seal with shellac then scrape with razor blades. The scraping is easy after a little practice. You can even make a blade holder which adjusts for the width of binding, which helps with the bulk of scraping, to be finessed by hand.

I made a bladeholder like Michael's and it works good (his is prettier though). I also use mine for scraping a rabbet around the bridge before I glue it down.

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Steve Smith
"Music is what feelings sound like"

Yes Steve, I use it for the bridge too, with the exposed area of the blade set to around 1mm or thereabouts. It works well for that.
Mike.

As mentioned, shellac the channels and use CA, then scrape level and prep. For shell work especially, CA makes life much easier in terms of leveling and filling. Once the body is prepped and sealed (do not spray colored lacquer directly on wood...you will thank me after your first ruined burst), a good mask just outside the desired trim line is done and the color coats are added.

Also think about the purfling scheme... an added thin black purfling line on a burst or other darker painted scheme makes it easy to get a clean scrape without revealing top wood, while something like a single light-colored binding strip without purfling forces the trim line to be inset from the edge of the plastic (see just about every painted Les Paul 's side scrape in the cutaway section and fretboard binding for a tutorial as to how the factory handles the job).

The most difficult scraping I did at Greenridge was on the rosettes of burst acoustic tops... no degree of fine line masking gets a truly clean edge on a ring-style rosette, so either the 'by eye and hand' method used by Gibson or a soundhole-mounted jig and thin-line scraper jig must be used.

What is not generally mentioned in these discussions is that lacquer has a defined window of time within which to get a clean scrape, and that window varies by lacquer used, thinner type and mix, any added plasticizer such as butyl cellosolve used, thickness of the coating, shop temperature, and air movement. Scrape too soon and the lacquer strings or is tugged/stretched, leaving a wavy or ragged line. Too much time between application and scrape allows the lacquer to harden to the point of fracturing and chipping out...even with a sharp, fresh edge on the scraper. A clean scrape is achieved only when the lacquer is at the right degree of drying and hardness to scrape without tears, pulls or chipping.

Where a color coat has gone too long to allow a clean scrape, a light coat of 50/50 clear lacquer can be applied to restart the clock, but keep in mind that the thicker the coating to be scraped, the more difficult it will be to scrape back, and the greater the number of top coats must be over the binding and purfling to allow leveling. Also note that after scraping, that first clear sealer coat needs to be light enough to avoid adding a bunch of solvent and allowing the color to flow, causing a soft edge, but with enough lacquer to get at least a full satin coat to seal. Subsequent coats can be the usual 70/30 full wet coat once that seal coat is on, and for bindings, a couple extra coats to build up over the scraped areas can be done with a round fan pattern and reduced pressure to minimize overlap beyond the binding and purfling.

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For the times they are a changin'

- Bob Dylan

^^^ WISDOM RIGHT HERE! ^^^

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"Act your age, not your shoe size" - Prince

I see the blade holder holding a single-edged razor blade. My experience with a Stanley knife blade instead of a razor blade to scrape with told me that the Stanley blade makes a far better scraper than a razor blade. For one, it won't chatter like the razor blade, nice and stiff.

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Peter Havriluk

I also like to use scraper blades that are thicker than a razor blade. I have them from 0.012" to 0.024" thick. And rather than a knife edge, I tend to do square edge and roll a bur using a burnisher. Old habits die hard.

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John