Making a double bass

[bmccarthy]

The suspense is killing me...

[Guest]

Hey Brian...My filler is ready and waiting...you too?

[Roger Hargrave]

Well I can understand your frustration. The problem for me is that I still need to make a light cabinet for the bass. The shed that I have chosen was delivered yesterday, but I still need to build it. Fortunatly my son is here for a few days and we will put it together, together. However in the meantime I am in the process of varnishing a viola. So today I will show how I am doing this, which may help to ease the frustration. I will then add the bass pictures when I get around to completeing the job. I hope that this will be OK. So please check modified post #197

[Roger Hargrave]

Whenever I’m varnishing, I often find myself trying to reconcile the two conflicting principles that I mentioned earlier. The first is trying to produce an attractive varnish that also enhances the instruments sound. The second is simply to recreate a fine classical Cremonese varnish. Obviously these great Cremonese varnishes are what inspire and motivate us. Nevertheless, our first priority is to find something that works well both tonally and visually. Not a particularly difficult predicament then!

 

Some thirty years ago a member of the Hill family gave me several samples of classical varnish. They were pieces that had been removed from cellos in the 19^th century. When Professor White analysed these samples and others that Beares provided, he provided us with a rather complex set of results. (See White and Dilworth, The Strad Oct 1984, pp.437-438)  In fact over the intervening years many more analyses of various instrument coatings have been undertaken. The internet is bristling with them. Probably the best place to find a comprehensive introduction, are the VSA Papers that were first published in the summers of 2007 & 2009.  Compiled by Bruce H. Tai, they have the advantage of being both comprehensive and lucid. Otherwise, almost without exception, the findings of most analyses are both complex and difficult to interpret.

 

According to White the varnishes that he examined largely consisted of a drying oil, colophony and a small, almost insignificant, amount of mastic resin. This may seem to be a relatively simple, however, if we examine the first ingredient, a drying oil, we notice that there are already several possibilities. These drying oils are many and varied and amongst others they might include poppy and walnut oils, or the more conventional linseed oils. Walnut oils were used by many Venetian painters, whereas linseed oils were preferred by Cremonese painters. These preferences were largely due to the general availability of these drying oils. For example, Cremona was an important centre for the production of linen and linen is made from the flax plant, the seeds of which (linseed), are the source of linseed oil.

 

Not only did these basic oils have different characteristics of drying, transparency and different cracking and aging properties. They also reacted in different ways when combined with other ingredients such as resins and pigments. However, even if we confine ourselves to linseed oil, there are also numerous possibilities that require consideration. In the first instance, how was the oil extracted from the seed? Was it cold pressed or extracted by various heat and chemical procedures? Then there are the various possibilities for treating the oil after extraction. These treatments might include washing the oil, boiling it, or thickening it in the sun. Consequently, the selecting the first of our three initial ingredients is beset with difficulty. But even after selecting all three ingredients, our problems are not over. We must still decide how much of each ingredient will be added to the mix, and how and at what stage and temperature they are to be combined.  

  

I could go on forever outlining the infinite possibilities that even three relatively simple ingredients can create. And, if finally, we add various pigments, the passage of time and various environmental effects, it must be clear to everyone that even the finest, most detailed analysis, can only offer us a tiny insight.

 

Back in the 1970’s and 80’s we were desperate. Accordingly, after several long distance telephone conversations with Professor White, (an expensive business in those days) I finally persuaded him to give me a simple breakdown of his results. And, very reluctantly he also discussed possible recipes with me. From our conversations and from various ancient recipes, I created the following basic varnish. I doubt that the eminent professor would support my speculative conclusions; he is too much of a scientist. Nevertheless, at that time I needed to use the available information to the best of my ability and in the end I came up with the following fairly simple varnish formula.

 

According to White the varnishes that he examined consisted of a drying oil, colophony and a small, almost insignificant, amount of mastic resin. Eventually I made a varnish that, by weight, consists of 55% colophony cooked together with 40% cold pressed and washed linseed oil. To this I added about 5% of mastic tears. This came to a (by weight) total of 60% resin to 40% drying oil. These amounts were guesstimate based on the available information, coupled with several ancient recipes, of which there are many.

 

The method(s) I used for combining these ingredients was based on two or three further snippets of information. The first of these concerned the length of the colophony molecules. These were not found to have been significantly altered. Accordingly, White had concluded that the colophony had not been cooked at a high temperature. He suggested that it had probably been heated just hot enough and long enough to blend it with the oil and mastic. (His conclusion about the mastic was that it had probably been added as plasticizer.)  

 

In addition to this important observation about the cooking process, at a later date Professor White was asked to examine a particularly red and rather typical Venetian varnish on a violin by Sanctus Seraphin. White was specifically asked to identify the colouring agent. His reply was illuminating. Having examined the instrument he concluded that the redness in the varnish was simply the result of oxidisation, rather that any additional colouring agent. For me personally this was a revelation. 

 

A further characteristic of linseed oils that should be considered is the fact that as well as becoming increasingly darker with time, they also become more transparent. The problem for any violin maker attempting to emulate Cremonese varnishes is that this oxidisation is the natural consequence of time; hundreds of years of time. Replicating this natural oxidisation over a much shorter time scale is extremely difficult, if not impossible. Indeed, over the intervening centuries, emulating the effect of age and oxidization may well have been the major problem for violin varnish makers. As a consequence, violin varnish makers have developed numerous artificial methods of emulating this aging process. Some are more successful than others, but they all involve compromise.

 

These limitations are further frustrated by the fact that pigments were probably added to some, if not all varnishes. Undoubtedly, these pigments will have varied considerably in both quality and type. They may simply have faded and/or the medium in which they were locked may have altered their properties markedly. In turn any additional colouring matter may have altered the configuration of the varnish itself.

 

All of these considerations are worthy of investigation, but what I would like to offer here is a simple varnish that not only works well, but is flexible enough to allow several variations to be developed. So let me begin with how I prepare the linseed oil. I always use artists’ quality cold pressed linseed oil. I then wash the oil twice. Although it takes time, this process is relatively easy and is described many times on the internet. I mainly wash the oil because it increases its transparency. I also filter my finished varnishes to further increase transparency. Again all of this is about creating the appearance of age. Effectively it is just another compromise solution. In a dark cupboard this washed oil and/or finished varnish, can be stored for many years. However, it is important to leave as little air in the jar as possible.

 

Although there are several alternatives, I mostly use colophony as my main resin and this is the basis of the varnish that I will be using for the bass. Colophony has a similar refractive index to Venetian and Strasburg turpentine’s, but it is probably the easiest usable resin to find and to work with.

 

Having decided how much varnish I wish to make, I cook the resin low and slow. It will gradually reduce in volume considerably. Especially in the early stages this cooking process will give off many highly inflamable gases. If you decide to attempt this you will need to be very aware of the possibility of fire or even an explosion. Clothing especially wools and cottons can absorb fumes and become highly flammable. You should always have a fire extinguisher capable of putting out an oil based fire. You also need to be aware of the possibility of an exothermic reaction. Several violin making students have been badly burned cooking resins. If you do not have access to a laboratory extractor this needs to be done in the great outdoors. Cooking colophony in towns and cities is likely to cause problems with neighbours and authorities. Initially the colophony will melt and highly inflammable turpentine’s will be released. If you alow the colophony to get too hot it will burn and turn an ugly black/brown/green color.  

   

Now in order to simply combine the colophony (and eventually the mastic) the colophony and other resins can be powdered and gradually added to hot linseed oil until they blend. However even this is not always as easy as it sounds; if the oil is not hot enough the various parts will separate on cooling. Nevertheless, eventually this method with give you a good varnish. It will also be a varnish in which the molecules of the colophony have not been markedly altered. Unfortunately, when applied to a violin this varnish will be almost as clear and colourless as cold pressed and washed linseed oil. In other words it will be boring. Even with a fine ground colour it will be boring. This leaves us with two possible methods for creating that illusive appearance of an ancient oxidized varnish. We can either colour the varnish, by adding a colouring agent. Or we can attempt to oxidize the varnish using various artificial methods.

 

The choice is complicated by the possibility of employing both methods; oxidizing and introducing colouring agents. There is undoubtedly some evidence that classical varnishes were coloured. Today, probably because of their tendency to be naturally transparent, the most commonly used violin varnish colouring agents are lakes. Theoretically the process of lake making is relatively simple, but in reality it is extraordinarily complex. I am not about to enter this debate. I have made an enormous number of both natural and synthetic lakes using every possible combination of base material, salts, liquids and temperatures. The most talked of lakes have always been madders. Today we are lucky to find one or two suppliers of madder root in the world. However in the 16^th century there were more than forty varieties in Holland alone. And herein lays the first problem of creating high quality lake pigments. Many of the raw materials are simply no longer available. Kermes and now even Pernambuco, seed-lac or stick-lac are extremely difficult to obtain. Moreover the recipes are often highly complex. It is not without reason that highly trained colour masters often specialized in creating only one group of colours. 

 

Mineral colours are also a possibility, but those from ancient natural deposits are also unlikely to be available.

 

All of these colouring possibilities are likely to be affected by the mediums into which they are ground. Consequently if you do find a colour that meets your needs, it will not only be a matter of luck, it will also be a matter of compromise.  

      

This leaves us with emulating the process of oxidization. There are many ways of approaching this. For many years nitric acid has been employed in spite of the fact that it was not available to the classical Cremonese makers. Creating violin varnishes with the help of nitric acid has taken many forms. It has also been used in various ways to colour the wood before the varnish is applied. Amongst the most famous formulas are those described by Fry in his 1904 book “Italian Violin Varnishes”. In the dim and distant passed I have had some success with this book. However, I would add one massive caveat; nitric acid is extremely dangerous and can create explosive substances with a great many organic materials. This includes nitro/colophony. 

[Carl Stross]

Thanks Roger ! Great insight for people like myself, in the working methods of a true Master. One thing : must be rabbit pee ? No shortcuts allowed ?

[Roger Hargrave]

Thanks Roger ! Great insight for people like myself, in the working methods of a true Master. One thing : must be rabbit pee ? No shortcuts allowed ?

I tried horse piss and it works well. I use rabbit because it was available and because Aubert used to use it for colouring their bridges. 

[JohnCockburn]

I tried horse piss and it works well. I use rabbit because it was available and because Aubert used to use it for colouring their bridges. 

now you've really put me off licking the feet when i cut them.

[Roger Hargrave]

now you've really put me off licking the feet when i cut them.

 

Aparently this stopped at least 35 years ago. I talked about it with a ninety years old member of the Aubert family in the early 1980's. He said that they had stopped doing it, but he insisted that the old way was much better.  

[Carl Stross]

Aparently this stopped at least 35 years ago. I talked about it with a ninety years old member of the Aubert family in the early 1980's. He said that they had stopped doing it, but he insisted that the old way was much better.  

 

 

Roger, tell us please if you know : how did they harden the bridges ? Was urine one of the secrets ? 

[Guest]

Roger

When pre-cooking the resins what temperature do you consider low and slow? Also when cooking the resin and oil do you cook until the firm pill stage, that is until you are able to pull a string?

Thank you for writing more. What a treat it is to read all this over Sunday morning coffee.

[Roger Hargrave]

Roger

When pre-cooking the resins what temperature do you consider low and slow? Also when cooking the resin and oil do you cook until the firm pill stage, that is until you are able to pull a string?

Thank you for writing more. What a treat it is to read all this over Sunday morning coffee.

 

I do not cook the oil more than is required to blend the colophony. I cook the colophony well beyond the stringing stage. When it strings the strings break like glass. 

[robertdo]

Just to illustrate the yellowing of linseed oil in the dark described by R. Hargrave, here is a picture. the pot on the right contains linseed oil that I leave behind the window (it will thicken) and on the left is the same starting linseed oil sunthickened that had the same color, and then was left in the cellar for few months.

[CarloBartolini]

Roger, thank you for the great thread, and all the wonderful varnish info. I know it's obvious, but the value of this thread is gigantic, years of experience narrowed down and well written, it is a great gift to all of us, thank you.

 

I notice you do not mention liming colophony, you do not? Any issues with varnish being thermoplastic? Something I'm missing?

 

Thanks in advance.

[Roger Hargrave]

I am not happy with the idea of either wood or varnish ingredients being treated with nitric acid. Nitric is extremely aggressive and at some point these treated substances will come into contact with the musician’s skin. In the 1980’s nitric acid was used to stain boxwood chinrest, tailpieces and pegs. I have often wondered if these might have been the cause of those unsightly marks on the necks of so many violinists. In fact since the 1980s I have not used boxwood fittings on my instruments unless they were specifically requested.  

 

That said, simply adding several drops of nitric acid to varnishes appear to accelerate the process of oxidization. Depending upon the amount added and the time it is given to work, it will certainly eventually create a deep red varnish. But as I have suggested nitric must also attack the basic structure of the varnish. Consequently this process a bit hit and miss. Moreover, it does not have a proven long term track record. For this reason alone, I am not sure that I would recommend it.

 

But then the method that I use also brings me into conflict with the method of cooking colophony as it was interpreted by White. In order to darken it sufficiently I cook my colophony for a long time. The cooking time required depends upon many factors including the outside temperature, the quality of the raw materials, the method of cooking, and the amounts being cooked. However, I am fairly sure that the time and heat required to darken the colophony significantly would almost certainly alter the colophony’s molecular structure 

On the 12^th of April Lyndon wrote the following;

Joe Robson and others have introduced me to the idea that deep colours similar to nitric acid treated varnish can be produced simply by cooking the raw rosin at high temperature for a long time(forgive me if I'm oversimplifying Joe) So yes it may be possible to get the deep Cremonese reds with hardly any pigment, and no nitric acid. I have unfortunately never seen samples of varnish produced this way, to see if it is just as beautiful as results I've got with nitric acid, however it would fit the bill of the elemental analysis of the original Cremonese varnish having little or no pigment.
 

Well I beg to differ. The problem is that it is extremely difficult to get all of these factors right, and no-one can tell you exactly how to do it. I am sure that with the correct laboratory equipment you could introduce several guiding principle, but Koen Padding was the only person I know that was capable of working in this way. The necessary equipment for such work is very expensive and consequently it is difficult to justify for the small amounts that most violin makers require. I have had many batches spoiled by cooking the colophony too hot or not long enough, but with experience it does get easier.

 

Here I wanted to included the photo from the post 

A repository of caveats, version II post # 23

because this is very much how my finished varnish looks. It is red in thin layers when the glass is tipped; otherwise it is too dark for light to pass through it. My varnish is always fairly thick. For those that know Koen’s varnishes mine are much thicker. They normally require only one coat although I usually use two coats for cellos. My varnish has the consistency of household gloss and I usually apply it with a stiff brush.  

Photo 1 is my number one varnish store. It is is a cupboard with an added curtain. I have varnish in jars that have been in this place for at least twenty years. They dry in UV in 6 to 8 hours. 

Photo 2 is the shed waiting to be assembled. 

Photo 3 the test I made before painting the rabit piss on the viola. It gets darker in the UV. See viola colour on post # 197 this post has been altered recently.

[Alfieri]

All about linseed oil from a expert artist.

 

http://www.tadspurgeon.com/justoil.php

[Roger Hargrave]

Roger, thank you for the great thread, and all the wonderful varnish info.

 

I notice you do not mention liming colophony, you do not? Any issues with varnish being thermoplastic? Something I'm missing?

 

Thanks in advance.

 

No, but I do like to keep it all as simple as possible. Too many things mean more to go wrong . 

[Roger Hargrave]

Roger, tell us please if you know : how did they harden the bridges ? Was urine one of the secrets ? 

 

What the old man Aubert told us was that; the uncut blanks were laid down in layers. Wet rabbit dung, followed by straw, followed by bridge blanks, followed by straw, followed by dung, followed by straw, followed by bridge blanks, etc, etc, up to three meters tall. The stacks were left for two or three years and apparently they gradually became much lower. He said that they were covered at the top,  but were otherwise exposed to the air This also coresponds to the fact that oak house beams in Northern Germany were laid for several years in dung. It was said to prevent worm attack and to harden or strengthen the timber. The old man complained bitterly that the bridges were now (1982) simply dipped for a few hours in tanks of amonia. He showed us the tanks with bridges suspended in the liquid. But I have no-idea how long they were eventually left in the tanks. At that time we purchaced a number of bridges and they smelled strongly of amonia. Later this smell disipated.     

[Rick Hyslop]

Sounds like a very funky lasagna.

 

r.

[Rick Hyslop]

By the way I have read your a great deal of your writings. Thank you for being so public with your extensive knowledge.

 

r.

[Roger Hargrave]

All about linseed oil from a expert artist.

 

http://www.tadspurgeon.com/justoil.php

 Yes that is worth a look. It is just wonderful how much info of this quality is out there for free. Nothing like that in my day just seaching the libraries and the books. I enjoyed it, but it took forever. 

[fiddlecollector]

Roger just want to point out that Nitric acid has been around than a millenium and started being  produced  more commercially in the 17th century using the Glauber process which is basically the process used today. So its not totally unconceivable it may have been used for some processes in the art material world.

[fiddlecollector]

Regarding rabbit piss, i treated wood years ago with it due to having a readily available source at the end of the garden. It has interesting properties ,eventually producing  a hard mineral ground on the wood surface after repeated soaking of the surface and drying/uv ,it becomes transparent under oil varnish.

[Melvin Goldsmith]

 Yes that is worth a look. It is just wonderful how much info of this quality is out there for free. Nothing like that in my day just seaching the libraries and the books. I enjoyed it, but it took forever. 

To right Roger! But not just in your day ( which is still continuing hopefully!). I guess I'm a couple of decades younger than you but still remember making my first madder lake from library information, the wait for books to arrive etc and still then I was mainly using detective work from dyeing manuals....now it is possible to google a recipe or order some nice stuff almost instantly....I'm not sure how I feel about that really sometimes!...but on the other hand it is great to have so much information increasingly at hand and to be able to benefit and learn from the resources like MN and especially your input on this thread here....Thanks & OK...I'm off to get some Rabbits.

[Carl Stross]

...I'm off to get some Rabbits.

 

Unless you're into very tiny violins, I'd say better get a horse.

[Rick Hyslop]

I have a serious question. Would any urine do the trick why specifically horse or rabbit ? Is it the grassy diet ? Why the straw and dung then ? Is the secret in the straw ? Boiled straw tea solution ?

 

r.