SMOOTH OPERATOR

One of the most debated issues within the violin making community concerns the varnish. Yet these discussions are not all about what it’s made of or how to apply it. Many hours can be spent contemplating, debating and experimenting with the finishing of the wood surfaces prior to varnishing, after which we have a violin ‘in the white’. This is an important foundation stage which has a considerable impact on how the final varnish will look and feel. Many luthiers consult the historical records of the old Italians for inspiration and guidance, and there are many myths and legends that contemporary makers often draw on. Here we find references to the use of a particular grass in the process of finishing a violin in the white, which we have come to ascribe to the plant equisetum hyemale, or ‘rough horsetail’ to give it its common name. Undertaking historical research to inform our current practices is a great place to start; however, following the clues as to how it was done in the past doesn’t automatically bring with it an understanding of why, nor of how, to make decisions regarding which practice is best for which circumstances in our own workshops today.

Finishing is a process that brings makers up close with the wood we are using in a very specific way. Understanding how to highlight the grain in different ways for different reasons creates a space where we can appreciate the materials we work with on a deeper level. Through this process we can connect with each individual violin on our workbench, and make choices that celebrate its unique structure and origin as well as the history of our craft. I believe it is important to be able to make these choices in an informed and deliberate way, so that we are then able to enjoy executing these processes with skill and confidence. This approach brings with it a greater chance of achieving the result we are aiming for. When I have taught violin making, I have often seen many beautifully crafted violins being disregarded because of disappointing finishing and varnishing (this includes my own student work). These processes are not easy to master, yet their success will ultimately determine whether a player will pick up your instrument, or not.

So, how do techniques for finishing a violin in the white impact on the final varnish? For the answer to this, we need to look closely at the cellular structure of the wood and understand how each technique will change its surface in preparation for varnishing. Before we venture down that rabbit hole, we need to take a step back and clarify what violin makers are generally trying to achieve with their varnish.

If you have ever examined a violin crafted by one of the great Italian masters, you can appreciate the stunning quality of their varnishes, which just cannot be captured in photos. They have a brilliant depth of colour while remaining strikingly transparent, such that they truly enhance the beauty of the wood underneath. These two aspects of varnish do not normally go hand in hand. Here is where the tricky part begins: achieving this depth of colour either requires increased levels of pigment within the varnish itself, or increasing the depth of the varnish – or both. However, these options decrease the transparency of the varnish. Another option is increasing the depth of colour at the wood’s surface, but there is the risk that if it is not done well, it will ‘kill’ the movement of the treasured flame in the maple, and produce uneven dark patches at the end-grain areas of the arched spruce front. Modern varnishes and lacquers overcome these difficulties through various materials and techniques that aren’t really an option for violin makers. Apart from the obvious visual mismatch with the ethos of a hand-crafted instrument, it impacts on the violin’s sound quality. This means we must master the skills and materials that have been used within the lutherie tradition for centuries. And this takes understanding and time.

ACHIEVING THIS DEPTH OF COLOUR EITHER REQUIRES INCRE ASED LE VELS OF PIGMENT WITHIN THE VARNISH ITSELF, OR INCREASING THE DEPTH OF THE VARNISH – OR BOTH

As I mentioned earlier, historical research is helpful in developing understanding, but some modern research can also provide valuable insights. First, understanding how light reflects and refracts means we can make important decisions around the varnish we use – but also, and more importantly, about how we finish the wood’s surface. When the surface is rough, light coming through the varnish reflects back at a variety of angles from the rough areas, and appears more diffuse or less transparent. When using a clear resin varnish finished to a smooth surface, this can be overcome by applying one with a low molecular weight. However, if there are more particles within the varnish, such as colour pigments, then the number of different angles of reflection increases once more – as seen in figure 1.

FIGURE 1 How the particles in a varnish can increase the number of angles of reflection

From these research studies, we can reason that the smoother the wood’s surface, the more transparent the varnish will appear. The choice of varnish is obviously the most important aspect of the violin’s final appearance, but if transparency is what you are aiming for, smoothing the wood’s surface as much as possible will provide the essential foundation. It also enables us to apply coloured grounds more evenly, and without killing the flame.

So, what exactly is meant by ‘smoothing’ the wood’s surface? At this point we have circled back to the theory about looking at the cellular structure of the wood, and to the use of equisetum. First, though, we need to establish some key terms and processes. Before finishing the wood’s surface, we need to shape it by the process of selectively removing wood. This can be done by cutting, chiselling, gouging, planing, rasping, filing, scraping, using abrasives (e.g. sandpaper) and more. We progressively move from taking smaller and smaller bits of wood away through each process, until we have the desired shape.

Once we have finished shaping by removing wood, then we can ‘smooth’ the surface. This is burnishing. To burnish something is to rub the surface until it is smooth. There is no removal of material; the cellular structure of the wood is simply ‘deformed’ so that it is compressed and therefore looks smooth and shiny. Let’s take a closer look at some of these processes and how they affect wood at a cellular level.

As spruce has a broad range of densities across the annual growth rings, it offers a useful way of demonstrating how the wood density impacts on the efficacy of each of these processes. We can then extrapolate these results to different wood species. As can be seen from Table 1, if you are looking to smooth the surface, then burnishing is the process of choice. I used a bone handle for these small experiments but there are other options, such as plain paper. The harder you burnish, the more compressed the wood becomes, and the shinier the surface will appear. If you want your varnished violin to look extremely smooth and shiny, this is the process for you. You could also burnish specific areas to achieve this type of look in targeted areas. One step back in smoothness from burnishing is using a scraper after planing. I have known makers who use this combination of processes to finish shaping, and then they burnish their violins (not quite as vigorously as I have in these photos) so that they can compress the wood enough to apply ground colours evenly, directly to the wood.

MANY PEOPLE TALK OF REHYDRATING THE STALK, SO THAT YOU CAN CUT IT OPEN INTO A FLAT PIECE WITHOUT IT BRE AKING

Returning to equisetum, we can see a similar result to 400-grit sandpaper. It is a good abrasive for the removal of small amounts of wood and works as such through the plant's natural accumulations of silica on ridges all around the circumference that extend along the length of the stalk.

If your preference is to not use modern abrasives then equisetum is a good alternative. But be warned: it is not a convenient one! I like to take my time to enjoy the process of hand-crafting my instruments, but after sourcing, drying and processing equisetum, I would question whether it was worth the effort. I will leave that for you to decide, and in the meantime I will explain how.