Why some guitars are better than other

Whether you are a guitar player or not, you might have wondered why most guitar players prefer to play old guitars. You see famous guitarists playing guitars that are many, many years old, people who with all the money they have could afford to buy 50 new guitars, and you think why drive a 20 year old car when you can afford to buy the latest model, which comes with Siri integration, Google Maps and a Spotify premium account?

And the answer is precisely that, because a guitar has nothing to do with a car. Apart from the fact that a guitarist can become familiar with, get used to or become attached to his guitar (which is normal after spending so many hours with it) there is another fundamental reason: guitar woods sound better over time, so unlike cars, guitars improve over time and become more valuable as the years go by.

What happens to wood as it ages?

Wood is mainly cellulose, hemicellulose and lignin (apart from other minor components). Hemicellulose is found throughout the wood, acting as a binding agent for the fibres, and over time (always after the wood has been cut of course) it evaporates.

As it evaporates, the wood loses weight, but retains its stiffness. By maintaining its structure and being lighter, it acquires greater freedom to vibrate, so that some frequencies that were previously more muffled start to resonate more, and the wood sounds better as a whole.

On the other hand, once the tree has been cut down, the sap stops travelling through the trunk and over time begins to crystallise, which also helps to stiffen the wood and improve its acoustic capabilities.

In addition to this accumulation of processes, lignin also modifies the initial structure of the wood as it degrades when exposed to sunlight. We often identify the «age» of a guitar at first glance by the colour of the wood. Spruce, for example, in new guitars is white and with time it acquires a yellowish, almost orange tone, and ends up being brown (although the varnishes used also have an influence here).

But can this effect be achieved artificially?

There are guitar makers who use a process of treating the wood called torrefaction. They use drying kilns to house the wood and dry it at very low humidity levels, they «cook» it at high temperatures controlling the oxygen so that the temperature and absence of humidity help the evaporation of the hemicellulose and the crystallisation of the sap more quickly, let’s say that it is not achieved artificially, but rather the wood is left in conditions that favour the natural process, to «give it a little push».

Guitar makers have been trying all their lives to find ways to accelerate nature’s process and obtain woods with better acoustic capabilities, without having to age along with them. It is said that the master Antonio de Torres used to put his woods in the Almeria sun to «favour» the process, but if true, this would only help the degradation of the lignin.

In the absence of a definitive «catalyst» capable of producing the crystallisation of the sap, the evaporation of the hemicellulose and the degradation of the lignin, we will have to continue to focus on humidity to shorten the waiting time, to try to shorten the path.

We must not forget that wood is still an organic material, which acclimatises and adapts to its environment, temperature and humidity (even after cutting). If there is a lot of humidity in the workshop, the wood swells or expands, if there is little humidity, it shrinks or contracts, in fact, this is the main reason why the wood of your guitar can crack. If the guitar was glued or assembled in a humid environment and your guitar is in a very dry area, the wood shrinks (naturally) but because it is already assembled and anchored on the sides, the wood is not free, and it creaks as it shrinks, causing cracks in the back or top.

Let’s say that humidity is dynamic, the wood can have more or less, rise or fall, but the ageing and crystallisation processes are only in one direction.

It would be necessary to compare what is better for the sound, a wood cut 30 years ago, but with no control of humidity and temperature, or a 10 years old wood cured in ovens and with total control of humidity and temperature.

Finally, I would only add that a 15 year old guitar that has been played every day will not be the same as the same guitar for 15 years, in the same place and conditions, but without being played, the natural crystallisation processes may be the same, but the guitar played for 15 years will sound much better than the other one, why? That’s for another day.