The Documentary of Hauser Restore

Japanese Version is Here.

February 28 1998 / Version 1.08

Author: Andrea Tacchi - FIRENZE/ITALIA

Produced by Makoto Tsuruta/CRANE Home Page

Type of instrument

Classical guitar made in Reisbach Vils Germany by the well known Hermann Hauser second in 1957 (20 september 1957 is marked on an inside hidded wood label) number 601.

String lengh 646 mm

Weight 1510g


Top: German Spruce (Picea excelsa).

Back , sides and bridge: Brazilian Rosewood (Dalbergia Nigra).

Neck: African Mahagony Boss (Guarea Thompsonii).


Mr.Robby Favery [Amsterdam].

Reasons for undertaking treatment:

To re play the instrument in records and concerts.

Condition of instrument before the treatment:

The guitar was completely coated with poliurethanic bi-component lacquer (frets and fretboard included).

roughly disassembled and opened with a knife by the binding of the back;

the back presented many long cracks badly carved by somebody ;

crack's were present also in the top, deglued fretboard, back bars and many other smaller problems as to make a correct fingerboard.

No signs of woodworm attack were on the instrument,

but the environment where the guitar passed many years,

Suriname, (guayana)is really humid, and so the guitar support general small damages that this kind of climate cause.

Parts removed and newly made

just part of bindings of the ribs, two kerfed lining,frets,saddle bone and a kind of cellulose a paste between top and fingerboard.

Description of pictures taken during restore


Photo 01

Description of pictures taken during restoreAs said during presentation,the instrument arrived in my workshop already opened in the bottom, so I was able to shoot pictures inside;this is a spruce plate glued to the top under the fingerboard, the notices were wrote with a ballpoint pen.


Photo 02

The foot/neck is showed,you can see how rudely the guitar was forced (in a dry way)with a knife between back and sides with the resulting lining breakage.

All the neck,foot and head was mahagony.


Photo 03

A broken lining (african mahagony) part.


Photo 04

The two main top's crack, were already restored.

but roughly enlarged with a knife and filled with some spruce splint.

but the two top edges were'nt glued on the same level.

and so after that the restorer (the previous one, not me!) who made the work levelled the outside with an heavy sandpaper action.


Photo 05

The fingerboard was almost completely deglued.

done by the extermely humid climate of central America.


Photo 06

As told, all the guitar was coated with poliurethanic lacquer, also frets!


Photo 07

And also the top, bridge and bone saddle was covered with a thick layer of varnish.
You can see on the treble side one of two big cracks.
These two previously restored cracks were making noise (fuzzing, vibrations) if the top was beated by tapping with fingers.


Photo 08

In this magnified picture you can see a close up of spruce top;

the rings were really narrow and hard,this is a topical conformation of German spruce which has during its life a harder climate than other Alps spruce as the one used by the famous Italians violin makers coming from Val di Fiemme in Dolomits.

and it's sound speed(the Hauser wood I mean) was 1500m/s across fiber and 5200 along.


The german spruce has always really high sound speed inside itself.

(around 5600-5800 meter/second along the fiber and until 2100 m/s. across the fiber measurement taken with the "elasicity wood tester" an electronic device built and commercialized by an Italian bow maker from Cremona Mr.Giovanni Lucchi).

may be a little faster than the Italian spruce.

but the second one has a different relative weight (specific gravity).

German spruce is almost always over 400 Kg/mc and often it arrives to 430 kg/mc;

Italian spruce weight range is 340-390kg/mc.


So, if you consider Young modulus is the sound speed squared multiplied by the specific weight (sound speed xsound speed x spec.


you obtain that German spruce is stiffer than Italian across and along fiber .

(not as much anyway, because sound speed is most important value being squared and ,it is similar).

but if you consider the ratio between sound of speed and weight,in the Italian spruce this is much more higher.

and this mean an easier entering in vibration for the wood itself.


For they that want to know more about German spruce.

I can mention the Rosamunde Hardling book where it's written than the greatest piano makers of last century were searching for spruce.

in the forest of "Duke of Schwazenberg", in Stubenbach and Lagendorf and , above all, Johann Segl who was living in Hohenam, in 1836 invented and built a saw with which it was possible to cut wood trunks.

and he was loking for spruce in the "Royal forest of Wolfstein"particularly in Schonberg between Rachel and Lusen mountain.

Another good book that I advice has been written in 1916, by the great Maestro Samuel Wolfenden with the title "The art of pianoforte construction" in some'll find really intersting data about wood and resonant plates, and sound speed in dissimilar materials.


Photo 09

Binding's macropicture


Photo 10-1

Photo 10-2

After to have deglued the bridge, who was not more glued with the original hide glue.

but with a vinylic, with the help of some water mixed with alcohol and a warmed spatula, first step of restore has been to glue some patches under the main top cracks.

So I made two thin slices of spruce and I glued these across the top grain with the help of go-stick on a mould radiused 6,5 meters.

Hide glue.


Photo 11

Photo 12

Photo 13

Photo 14

With a router I dug two canals deep until I got to the patch to remove all the old work which was making bad vibrations.

I made the canals pretty large (5, and 4 mm) to be able to clean it perfectly .

Later I filled them with two spruce pieces with hide glue.


Photo 15

Photo 16

It's better in this kind of work to wear microsurgery lens, these are from Carl Zeiss Germany and enlarge three times.

The tool I am using is a "painting restore knife", which, in reality is a really old razor (Moon brand from Solingen Germany) that I cut and sharpened in a particular way.

Only use not Inox razor, cause steel is harder.


Photo 17

The back:

first rule in restorage is to have it reversible, so even if I use a not reversible epoxi resin, first of all I seal the wood with hide glue.

The back presented many big cracks.

that a woodworker absurdedly enlarged carving these with a chisel with the goal to fill them with some rosewood splint, process that he never ended.

So after having sealed the two edges of every crack with hide glue, I prepared some epoxi glue mixed with microballons and staining powder as "terra di Siena"(burnst umber) and Brun Van Dyck, with which I filled all the enlarged cracks.

To do that, I pushed down the crack edges on the same 6,5 m radiused mould with go sticks.

Mould was covered with a thin polyethylene film.


Photo 18

the back after a light scraping and sanding action.


Photo 19

Some light patches made with cedrella were glued on the repaired splits.

Hide glue.


Photo 20

Photo 21

The original back brace (made of the same mahagony as the neck) arrived deglued from the back.

but still in good condition, so after a light flat sanding of the part to be glued.

I set them in the original position with the help of 6 reference block lightly glued on back.

On the opposite side of that brace a thin slice of spruce helped to make uniform the clamps pressure.

Hide glue was used.


Photo 22

The back almost ultimated;

in the neck foot area, maybe you can see a large patch made with a rosewood veener.

To glue it was necessary, cause the bad way in which the back was "pulled away" from foot caused many damages, for this I had to use epoxi glue.


Photo 23

Photo 24

All these block of reference made in cedrela were, necessary to assemble the back in the exact position regards the ribs,

infact, they protrude from the back profile just the same thickness of the original bindings which arrived in my workshop in good condition.

I lightly glued them with hide glue, easily removable after.


Photo 25

A newly made ribs binding was done, three maple veeners were glued together.

The central one was previously boiled in water dyed green with a cloths colour.

You can see it also in th the 36 picture.

This binding has been glued with hide glue and the help of masking tape.



Photo 26

A new back kerfed lining was glued.

It was done with Niangon(Tarrieta utilis)an African mahogany which was really similar to the original.

Hide glue used.


Photo 27

Photo 28

Two shot were taken with a low grazing light.

In evidence the particular way used by Mr.Hauser to shape his fan bracing and the round brace top under the soundhole.

No signs of possible later correction to the fan bracing done by introducing a small plane or sandpaper through soundhole by Mr.Hauser that can be seen.


Photo 29

Photo 30

Positioning and gluing the back, with the minimum stress was possible for the future instrument stability.

Hide glue used.


Photo 31

Gluing the original bindings.


Photo 32

Photo 33

When I removed the fingerboard which was already almost completely detached, and yet cut under the 12th fret,

I found this thin layer of strange material which seemed cellulosa or black glued dust powder.

Two years ago, I met in the town of Vicenza, where an important Guitar festival was being held, Mr. Hauser 3rd;

he showed a certain interest in my restore, but when I asked him what this material was for, he answered:

"This is a secret"-----!!!

I am sorry for the most curios of my readers, anyway, I can only give mine interpretation.

When you give a certain tilt to the neck, I mean an angle between neck and top, you must scrape and sand the part of fingerboard which stay on the top until it sits as a "instep" between feet and the sole shoes.

Only in this way when you press to glue the fingerboard you'll not give any stress to the neck and top, or, can use that compound, setting the neck in a suitable position.

I kept this solution, replacing the black material with some scraped,black dyed Azob veeners, a pretty light wood.

After that fingerboard was re-glued (hide glue), straightened,and new frets(Gebr Van gent Holland) were set.


Photo 34

The most pleasant part of my task:french polish.

I only use a kind of shellach which Mr Robert Bouchet adviced to me in 1983, and I use his same way to work, starting to fill the pore wood with pumice and alcohol.

It's a fast procedure and gives excellent results.


Photo 35

The bridge already coated was glued, lightly warmed, with hide glue.

Inside the guitar, not visible, a mould arched as the bridge isspreading the clamps pressure.

After that a new saddle bone was done (old ivory), a set of green Hannabach was tied, and the biggest miracle happened, the guitar was playing a loud, warm, wonderful sound , his aim was, despite the unfavorable circumstances of it's life, survived, hidded somewhere inside the instrument, to sing again.

Marvellous fact.

Some pictures of the ended restore.

Photo 36

Photo 37

Photo 38

Photo 39

Photo 40





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*Special Thanks: Mr.Kenichi Miyakawa, Mrs. Noriko Tanaka

* 1998 CRANE / TSULTRA Japan *

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