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Making a double bass


Roger Hargrave
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Thanks for writing about this, Roger! First, those photos are art. Nicely done. It's also refreshing to read your take on building a bass, what's the same as building a violin, and the unique challenges that it takes to make a bass. It seems like so often violin makers turn their noses up at making a bass ("It's carpentry, not violin making!"), yet few really try. 

 

I'm really looking forward to seeing how it progresses and reading about the lessons you've learned.

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  • 2 weeks later...

Today I am going to say something about purfling the bass. Although this job is not quite finished; we have to wait for the neck fitting to be completed, I want to keep the ball rolling. I apologize in advance to anyone who knows all this stuff and to bass makers who probably cannot believe the arrogance of someone writing about bass making the first time he actually makes one. 

 

I have always preferred making my own purfling. Somehow it just seems more natural. Generally factory made inlays are too uniform, too perfect. I usually prepare shavings about 3 cm wide and 50 cm long. I use a Lie-Nielsen low angle (Nr. 62) plane, which makes excellent shavings, but limits their width to about 3 cm. Although some makers favour wider shavings, I prefer these narrower strips. This is because I like to use freshly made purfling. Purfling that has been glued together for a long time can become brittle and consequently difficult to bend and cut. Although occasionally I still use shavings that were prepared more than 30 years ago, normally every three or four years I prepare a large batch of shavings of various thickness and materials. These might include strips of pear, beech, poplar, willow, maple and walnut, to suit the various models I might be expected to make.


It is easier to plane these strips from blocks that have been soaked for an hour or two in warm water. However, it is not good to leave them soaking for too long, because they may warp or twist. I overcome the problem of shorter soaking times by rotating the work. Since I am using different varieties of woods, at any one time I might have up to ten blocks in my bath, being held under water by a couple of house bricks. In addition, in order to make good savings the plane blade needs regular sharpening, it also needs adjusting to create strips of different thicknesses. This allows me to take a few shaving of each block and then to let it soak again while I work on the plane and the other blocks. 

Those shavings that I intend to stain I leave curled up as they leave the plane. If necessary I roll them a little tighter and hold them with a loosely fitting elastic band. This prevents them from unraveling in the dying process. It also helps with keeping track of the various thicknesses. However, if the rolls are too tight, the black staining will be uneven. Sometimes as with a Cappa copy, I want the individual black strips to be grey in the middle. I this case I weaken the dye and shorten the cooking times. In contrast the Amati family are known for the intensity of their black strips.


For this bass I used willow for the whites (0.8 mm) and pear (0.3 mm) for the blacks. Pear may or may not be what the Amati family used, but it stains exceptionally well and strongly resembles Amati blacks. My usual recipe for blacks is the one I was given as a student at the Newark School of Violin Making in England. So far I have not found a better one. The trick is to really wash the strips thoroughly after each stage and especially at the end. If this is not done there is a chance that the color might bleed into the instruments when either hot glue or hot water is applied.


1. Place the shavings in a mixture of 6 grams of potassium hydroxide (KOH?) per liter of water. This should then be boiled for at least one hour, after which it should be washed.  

2. To one liter of water add 20 grams of Log-wood chips. Boil the shaving in this mixture for at least one hour and leave them to soak for 24 hours.  Again wash the shavings carefully before the next stage.

 

3. To one liter of water add 12 grams of ferrous sulphate. Boil the shavings in this mixture for one hour and then leave them to soak for 24 hours.

 

4. Finally wash the shavings thoroughly and dry the strips. If they are not going to be used immediately clamp them lightly together between two flat boards. 

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Two days before I traveled to Rene’s workshop in Holland, I glued the shavings together, black white black. I then covered each strip liberally with hot gelatin glue and clamped them to the edge of the bench between two boards covered with plastic tape. Effectively, in addition to gluing these strips to each other, this process creates a sandwich that has a layer of gelatin glue on the outsides. This sandwich is left clamped for at least 8 hours. The plastic surface on the clamping blocks prevents the whole structure from drying out. Once the clamps and the blocks have been removed, (they slide off quite easily), the moist but not sticky sandwich is wrapped in kitchen foil. From the sandwich it is then a simple process to cut strips as and when they are required. In between times I keep the sandwich wrapped in the foil. Keeping the purfling moist in this way keeps it flexible and easier to slice, making beautiful slender miters relatively easy to create. 

 

It is always important to cut the purfling channel to a specific depth. Stradivari used single bladed cutters with a depth stop. For violins violas and cellos I use my copies of Strad’s cutters that were made for me by Mark Jackson, Mark makes many fine tools including superb spiral reamers. These cutters ensure that I don’t cut too shallow. If the channel is too shallow the purfling may fall out when the fluting is cut, and it will certainly not provide the protection that it is designed to give. Conversely if it is cut too deep the edge may become weak or even break off. However, as a concession to bass makers everywhere, I used a fine router for the main channeling and finished the corners and tricky bits by hand. I also used a double cutter to open (not cut) the channel slightly. 


Having cut the channel I prepared the miters and insert the purfling into the channel dry, making sure that it fitted right to the bottom. I then simply ran boiling water over the channel to reactivate the glue on the outer surface of the purfling. It works rather like licking a postage stamp. The boiling water also swells the channel and the purfling, clamping and gluing everything together. This process avoids excess glue penetrating the fluting and the end-grain of the edge work. There will be more on this purfling process later.

 

I allow any excess purfling to dry out completely before clamping it between two plastic covered boards for storage. If they are kept moist in foil for too long they will eventually go moldy. When they are required (even years later) it is relatively simple to rejuvenate them by wetting and then quickly wiping them dry before leaving wrapped in foil overnight.  

 

Just so that you all know this. The dots on the back, (lower left photo) are my blood. This tells you all two things. Firstly that I am (contrary to popular [popular to me that is] belief), not perfect. Secondly, that as can be seen from the color, I am not, as has also been suggested, of royal decent.    

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What do you use the old iron gauge for Roger?

When you say gelatine glue, what exactly do you mean?

Very cool work!

P.S. I have an iron one like this with the blade tips flattened, for making the purfling lines on on  purfled Testore models.

The iron gauge that you can see is one of several that I have pre-set for various models. And yes I have used it for Testore copies as well, (see my web site). I used to use them all the time for marking out my purfling. Today I just find them useful for easing a tight channel apart to make inserting the purfling easier. Gelatin glue is a general term for any form of animal or fish glue. For this job I used a simple freeze dried animal glue from Kremer. You don't need anything special for preparing purfling. 

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Much of the edge-work on this bass has been replaced, especially on the belly, and like many old basses it has not always been done well. Nevertheless, enough has remained intact for us to take a usable outline from the flat back. Indeed the fact that so much was usable, especially the elliptical C bouts, made recreating the overall outline fairly easy. What was not so easy was trying to balance both sides; that is to recreate the instruments original symmetry. Although the Amati family worked with great accuracy, no Cremonese instruments were ever totally symmetrical. Their method of making almost always created some asymmetry. (The reasons for this asymmetry are analysed on my web site at:

http://www.roger-hargrave.de   (The Working Methods of Guarneri del Gesù and their Influence upon his stylistic Development) 


Cremonese makers did not set out to make their instruments asymmetrical. In fact they made every effort to ensure that the bass and treble sides were mathematical mirror images of each other. However, whenever discrepancies occurred they were particularly adept at creating the illusion of symmetry with a few skillful strokes of the knife.

Because Cremonese moulds were the starting point of the construction process, they were always accurately made and mathematically symmetrical. This was the underlying reason why we wanted to recreate a symmetrical outline from this somewhat asymmetrical back. By folding the outline and by taking a mean between the bass and treble sides, to some extent we were able to correct variations between the various curves. Being used to viewing outlines from relatively close quarters, I was amused by the fact that laying the outline flat on the floor and standing on a table or a ladder was the best way of assessing our progress. Theoretically from this reconstructed outline we could then recreate a symmetrical mould.   

Essentially this process was the opposite of the Cremonese process. In effect we were attempting to make a symmetrical mould from an asymmetrical outline, rather than creating an outline with some ‘natural’ asymmetry, from a symmetrical mould. There are clearly several factors that make this process a little uncertain. For example we were working from the back outline only. Although from violins violas and cellos we know that the back outline is almost always closer to the mould outline than is the belly, we cannot be sure that Cremonese basses were constructed in exactly the same way. In particular this bass has features such as the bent flat back that link it to the Gamba family. 
 

Another factor that is difficult to assess, is whether or not the ribs, from which the back outline was finalized, followed the mould outline exactly, or if they were loose and or twisted on the mould. In the end any corrections were essentially a matter of judgement based on experience.


On this bass the unusual symmetry of the ‘C’ bouts was extremely helpful in recreating the outline and developing the new mould. They are also another strong indication that this bass did indeed come from an Amati workshop.

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From the reconstructed outline, Rene created a mould outline. He did this by reducing the outline by 7.5 mm, (representing the overhang and the rib thickness). He then constructed a mould out of plywood. Even with the large central area and the corner and end blocks removed, the mould was surprisingly heavy. This was yet another shock for a humble violin maker like myself.

 

Although I normally construct my instruments using the string and block clamping system used by Stradivari and described by Sacconi, (see photograph of my latest viola below),  this bass would have required mooring ropes from a battleship. In this respect I was happy to leave the rib bending and construction to Rene. In the meantime I was relegated to scroll making, (as previously described).

 

Having come from the same tree as the back and head wood, the ribs were a perfect match. Rene thicknessed the ribs with a thicknessing sander after which, we finished them with scrapers. Actually scrapers are really cutting tools and if well sharpened they should produce thin shavings. The problem is that sandpapering always leaves traces of abrasive crystals and wood dust in the pores. These deposits will eventually kill the natural reflection of the wood under the varnish. Although sanding in this way saves hours of time, the abrasive crystals embedded in the wood don't just kill its reflective qualities, they also blunt scrapers rapidly. Consequently  because we want to have the best possible finish, sharpening and re- sharpening my scrapers and getting first degree blisters on my fingers and thumbs was inevitable. This misery was compounded by my wish to accentuate the flames in the wood by holding the scrapper at the same angle as the flames. The best exponent of this art is David Burgess. Next time I'll pay his flight. The same thicknessing sanding treatment was also given to the back. However, like the head, finishing the belly was done totally by hand.  

 

As can be seen, for a violin maker this bending iron is big. It was formally used to bend the leading edges of 747 jet airliners. It requires the power from two atomic energy power stations to heat it to the required temperature. The bending strap is seen covered with the cloth that is wet before being applied to the rib and iron. For those interested in detail, the cloth was specially prepared by the company that makes the banqueting table cloths for the Dutch Royal household. Rene sewed two together.

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Splendid !!!  The wood selection is indeed quite nice. The scale of this sort of project makes me think about boat building...Looks like you guys are having fun !  What a lovely creation. I am impressed with the mold....no small effort expended on that baby I suspect. 

 

P.S.  I like the sippy cup hanging from the Bridge of the ole Gal in the background (see the photo of the mold )....two handled for the Grog no doubt !!

 

Thanks for sharing !  and a sincere thanks for your articles Roger. 

 

 

cheers !

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Fantastic, where do we send the check?

This is an interesting question. A truly hand made bass; from materials that would effectively have made at least six seriously fine violins; three years worth of violin and viola ribs; more than a dozen violin necks and scrolls, and any number of fingerboards. How do you assess its value in materials alone? As for the work, not to mention the travelling between workshops, my wife is pulling her hair out. It is almost as bad as writing on this web site and contributing to the Strad magazine.

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