Archtop restore job

[Beate Ritzert]

Hi folks,

recently i started to work again on my old archtop. The guitar has been my 2nd build (actually my first real guitar made from tonewood). Built in the kitchen with a very limited set of tools. Despite some flaws it plays pretty well.

Nevertheless, time goes by ... in this case almost 3 decades, and the old lady needs a bit of refinishing. And my demands changed - i am more in the need of a better acoustic tone while the instrument had been designed to be good when amplified.

Current state: the neck is freed from most of the (heavy) dents and sanded up to grain 1200. I plan to apply an oil finish on it instead of the former finish of clou nitro because i enjoy the better playing comfort of an poil finish. The guitar is still strung up.

Jazzgitarre_2011.2.jpg (14.82 KiB) Viewed 10449 times

As You might see from the photo the neck has not been set very well; it points toward the treble side. That makes it hard to place the bridge properly.

My current todo list:

- sanding og the headstock in order to apply an oil finish
- sanding of the rims which are heavily scraped
- sanding of the headstock in order to apply an oil finish as well (just because the neck is touched anyway)
- carefully sanding and re-polishing of the top, just using grain 1200 (wet). the response of the soundbox had been a lot better before the finish had been applied.
- some work on the frets. I had them replaced by a professional due to lack of time but never was happy with the result.
- a new bridge. A task that might probably better discussed in its own thread in its general aspects. For the short and instrument specific part of it - it needs to be asymetrically in order to compensate for the incorrectly set in neck. I intend to make it from Katalox, and i am not sure on the details of its construction.

Again: aim is to improve the sound of an already good guitar. I would like to utilize the potential of the soundbox better - i would like to obtain a bit more volume in the low registers, have a bit more warmth without losing its well developed ability to "cut through" in the high registers, while - of course - retaining the character of the instrument.

Despite of my willingless to reduce the damping of the soundbox by the finish (very!) carefully i consider my only options for sound improvements by optimizing the bridge and the strings (currently 15-56 La Bella Flatwounds).

Comments welcome.

Thanks

Beate

BTW: is it possible to use diluent for nitro laquer as a replacement of water in order to restore the finish of the top and the rims while sanding "wet"?

[Michael Lewis]

Hello Beate, first is the string alignment. They will tend to align between the anchored ends, so if you want the bridge to stay in line with the fingerboard/neck you will need to move the tailpiece over a bit so it aligns with the neck, or re-set the neck. One way is the "quick and dirty" method, the other is the more traditional method to correct the issue.

Regarding the finish: if there are any openings in the lacquer where water can seep through do not wet sand. Wet sand only when the wood can be kept from becoming wet. Lacquer will never last forever, so if you feel a need to make it nice you can strip the finish and apply a new thinner finish. I have used a 'short oil' varnish (Behlen's Rock Hard Table Top Varnish) with phenolic resin in the varnish, and it dries hard and much quicker than most other varnishes if it is applied in thin coats. Compared to lacquer it is less sticky on hands when playing, and if you like the feel of wood on the neck the varnish can be wiped on and immediately wiped off and let dry overnight. Two or three applications like this with sanding to 800 or so in between coats make a very nice and long lasting neck surface. There should be something similar where you are.

[Beate Ritzert]

Hello Michael,

Hello Beate, first is the string alignment. They will tend to align between the anchored ends, so if you want the bridge to stay in line with the fingerboard/neck you will need to move the tailpiece over a bit so it aligns with the neck, or re-set the neck. One way is the "quick and dirty" method, the other is the more traditional method to correct the issue.

With this instrument only the latter approach is viable. This is due to construction: the guitar has an oversized block filling the volume below the neck, and the neck is glued on also to the top. Which means that resetting the neck is almost impossible.

At present the setting of the tailpiece is more or less a compromise with regards to the limits set by (acoustically) useful bridge positions. The new bridge will become asymmetrical in order to account for this. BTW: that is my main motivation behind starting two threads: this one for the instrument specific issues and the bridge thread on what hopefully is of general interest.

I have used a 'short oil' varnish (Behlen's Rock Hard Table Top Varnish) with phenolic resin in the varnish ... There should be something similar where you are.

Yes, indeed there is something similar. I have been successfully using "Clou Hartöl" on two electric basses. Indeed, much nicer to the fingers and apparently also longer lasting than laquer.

Can i dare to use such a finish on acoustic tops (guitar, violin) as well without harming the tone?

[Michael Lewis]

As far as I know the only damage a finish does to tone or acoustic response is to add mass and acoustic damping from too much finish. The basic idea is to use as little finish as reasonable so the wood is covered and sealed but not built up so thick as to harm the acoustic response. Also thick finishes are usually more easily damaged than thinner finishes.

One approach to finishing is to apply the first coat and let it dry, then sand it level with the wood. Apply 2 or 3 more coats and after it is dry (cured) again sand it level. continue this process until there is no bare wood exposed after sanding, then add one or two more coats and sand level with very fine grit and buff. This method is designed to completely seal and fill the surface of the wood and build a very thin film of finish. It also requires a very fine degree of surface preparation, but provides a very nice finish that has a minimal effect on acoustic damping due to the very thin finish.

[Beate Ritzert]

Please let me continue at this point: frustration on a musical project. I needed to project that onto some rough work like removing the finish. So i continued with this one and ripped off the finish of the top. Head, sides an back will follow.

By tapping i notice that the back is more resonant than the top and i would like to learn a bit about tuning top and back (before bracing i actually tuned the back a third deeper than the top).
My idea is to carefully remove material from the top with a scraper and test the development of the tone. As i left the top thick (5 mm at the sides, 8-9 mm in the centre) and the bracing is strong there should be enough room left over for such a modification.

Is it possible to obtain a "ringing resonance" alone from the top if the movement of the back is strongly damped? Is it normal that the unbraced back of an archtop resonates louder that the braced top (deeper is not a surprise)? Are there any things i need to know about the spacial variations o f the tap tone, especially when the resonance of the back is damped? Anything else i need to know?

THX

Beate

[Michael Lewis]

When you tap one plate (either top or back) the other one will couple with it, which causes some difficulty to tell if one or the other is actually making the sound unless one plate is firmly damped. You also have the air in the body that resonates with the plates. Tapping the unrestricted body usually makes a full sound, because all the parts are working. If you restrict one part there will be less interaction between the other parts, and by doing so you can hear more clearly the response of the unrestricted parts. If you cover the sound holes with tape and tap the body you can hear the top or back without the resonant response of the air chamber.

Alan Carruth can explain all this much better than me. I just make guitars and mandolins.

[Paco Jimenez]

Yep, this is of great help.

http://collinsguitar.com/carruth-plate-tuning-dvd

[Beate Ritzert]

Looks as if it was...

What i do not see is terms of shipment and payment, especially world wide.

[John Mueller]

I found it listed for sale in the GUITAR SHOP tab.

[Beate Ritzert]

Meanwhile my nice lady is playable again. Thank You very much for the helpful duiscussion.

By tapping the top and the bottom i could successfuly improve the contribution of the upper half of the top to the sound - tapping the top is now a lot more uniform. Strung with '011 sized strings yields that fairly bright tone retaining the warmth i have always liked on the guitar - and it sound more "acoustical", a bit fuller - strings that thin were previously not usable on that guitar. The tone characteristics has remained more or less unchanged, the sound is just finer.

I am pretty sure that gauges up to '013 will sound good as well, and it will probably need these in order to achieve maximal loudness when played hard.

The oil finish was also successful - more even than 30 years ago and - more important - almost no effect on the sound.
@Michael Lewis: thank You very much for the encouraging tips.

A few thing remain to be done: the tailpiece shall finally be attached to the body by a string. An old plan which was unsuccessful when i built the guitar. And the re-adaption of the bridge to the top needs to be improved.