Construction & Materials
The importance of soundboard spruce
Varnishing and finishing
The process of finding the highest quality tonewoods for my instruments is a constant and often tedious process. Each piece requires specific characteristics that contribute to the sound, stability and longevity of the instrument. Not only is the beauty of a particular wood important, but also the physical properties of each species, the part of the tree from which it was cut, and most importantly, the method of cutting, which is critical to stability.
I am naturally drawn to wood and therefore this constant search for the most suitable and beautiful pieces is not a chore, but a very enjoyable activity that has taken me to many parts of Europe in search of the highest quality wood. Since my beginnings as a luthier I have stocked up on wood, so that today I have a large supply of beautiful, rare and well-seasoned European and tropical tonewoods to use for my instruments for many years to come.
Although I strive to use the most appropriate wood spices for each instrument based on historical models, since discovering and studying the inventory of musical instruments of Raymund Fugger (1528-1569), I have come to the conclusion that our ideas and perceptions about the materials used for instruments in the XVI century are still very limited and conservative. This inventory lists the hundreds of instruments in his possession, including 141 lutes. These come in all shapes and sizes and in a wide variety of materials, both European and exotic. In the latter category we find lutes made of sandalwood, ebony, pernambuco, whalebone and bamboo (Canna d'India), to name but a few. This demonstrates that instrument makers of the time were quite open to experimenting with materials that were considered very exotic, and that they probably used all available woods and materials to make precious instruments for their wealthy clients.
Knowing these facts has fundamentally changed my mind about the range of woods I currently use for my instruments, and the woods I would like to use in the future. Since the old luthiers were open-minded and innovative when it came to materials, I have no regrets about imitating that attitude five centuries later.
European and American tonewood dealers have developed a marketing strategy that has long misled not only instrument buyers but luthiers as well. It consists of dividing their spruce tops into grades (Master, AAA, AA, etc.) that have nothing whatsoever to do with sound quality and are based solely on aesthetic reasons. This attitude has led most people involved in building, selling and buying instruments to believe that a tightly ringed, evenly coloured piece of spruce is the absolute best and sounds better than any other. This could not be further from the truth. These are just external characteristics that have nothing to do with sound. The aesthetic superiority of close grained spruce can be debated, but its sonic superiority cannot be justified. If we take the work of the great lute and violin makers of the Golden Age as an example, we will observe exactly the opposite tendency: They almost always used medium to wide grained spruce.
Of great importance to the sound and stability are the straightness of the fibres (not to be confused with the annual rings), the precision of the cutting to the quarter, the ratio of weight to mass, and several other factors which are rather complex to explain briefly. If the tonewood manufacturers cut the wood correctly to obtain the best sound, the percentage of waste would be much higher, resulting in a less profitable business.
Thanks to the extensive testing and experimentation I have done in the past, I am able to find the right kind of spruce for the sound I want for a particular instrument. My soundboards for smaller instruments are split and machined by myself from a large billet of the highest quality, very straight spruce so that I retain complete control over the process. For larger instruments, I rely on a couple of very knowledgeable dealers who know exactly what I am looking for and can sometimes find me a few pieces that might meet my stringent requirements. That said, I still turn down about 75% of what they offer me!
Fortunately, the constant search is bearing fruit and I have managed to accumulate a sufficient supply to last me quite a few years, but I am still searching for that scarce and primordial resource that will be the most important foundation for a great sound.
Hot hide glue is my main glue, and is used for most of the joints of my instruments. This is the oldest glue known to mankind, and it is still superior to modern alternatives in many ways. It can make as strong a bond as modern glues and has the advantage of being completely reversible. One of its disadvantages is that it must be applied hot to work properly, and the joints must be joined quickly to prevent the glue from losing its strength. Another disadvantage is that it can fail in extremely high and low humidity. Fish glue is the other glue I use, and as the name implies, it is made from fish skin and bones. It is basically the same as hide glue, but can be applied at room temperature. From the tests I have done, it's just as strong as hot hide glue, but has the advantage of being less sensitive to moisture. That said, I currently only use it for joints that do not require the highest tensile strength.
I use traditional linseed oil varnish for the bodies and backs of my instruments. It is made from a mixture of linseed oil and various resins, and is the type of varnish used for lutes (and instruments in the violin family) from the Renaissance through the Baroque. Due to the influence of contemporary classical guitar making methods, the much more modern technique of French polishing is too often applied to modern lutes, vihuelas and baroque guitars. This spirit varnish technique has no place or meaning in the context of historic Renaissance and Baroque instruments.
The reason for using shellac ( French polish) is that its application is less labour intensive, while oil varnish takes much longer to dry, and both give quite similar visual results. The big advantage of oil varnish is that it produces a much harder and more durable finish when applied in numerous very thin coats over a long period of time.
Instruments that develop varnish problems after only a few years are usually varnished in 2 to 3 thick coats that never really dry completely. To avoid this, I apply a series of 15 to 20 very thin coats of traditional oil varnish (using a recipe from the early XVII century) and allow each coat to dry thoroughly before applying the next. This process can take anywhere from 7 to 14 days depending on weather conditions. It is a very labour intensive process, but the only one that ensures maximum transparency and durability of the finish.