[David Powell]

Originally Posted by Greg Clinkingbeard

I understand what David said, but it seems to be an exercise in theoretical physics.

Readily conceded. And I guess that is why physicists who are double bassists would carry out the exercise and patent various processes;- without proof. The thermodynamics behind the exercise are well known and in physics these are now called "laws";- meaning that the observed effect of heat and agitation on reactions that would proceed anyway over a long period of time is consistent. There are many plausible reasons why it could happen somewhat differently, though. And this is why it would be difficult to prove anything. Wood is not a consistent material at the molecular level. Because it is the product of a living thing it has all kinds of unstable stuff in it. If wood were crystalline in structure, that sort of structure locks the molecules in a way that agitation's effect would be canceled except at surfaces. But wood cellulose is a long chain sugar molecule held together by hydrogen bonds. It doesn't have a crystalline lattice structure like steel for instance. Steel rusts, but only where it is in contact with oxygen. And given enough time, it will rust no matter what you do. But painting the surface or coating it slows it down considerably. Oxides of iron are favored by thermodynamics over pure iron. It will not rust from the inside out, but it will rust faster at the surface in a warm and humid environment.

In the wood there are unstable chemicals that react with each other that are in close contact in the wood's structure. These are acids and (relatively speaking) bases right next to each other that tend to neutralize over time, a very long time, because the structure of the wood slows down the migration of reactants through the wood. So the reactions that happen within the wood as it ages happen pretty easily, depending on the moisture in the wood (faster if the wood is wet and warm) and other factors like the density and other components of the wood. It isn't necessary for the wood to be exposed to open air for some of these reactions to proceed. Attempting to seal the wood probably wouldn't slow it down much either. If you want to see an example of accelerated degradation of wood due to heat (and not much heat) simply place a freshly cut piece of spruce (2x4 from any hardware store that has a rapid inventory turn over will do) in the sun with part of it covered by something opaque and the other part exposed directly. Within a few days the exposed part will be darkened. The only energy added is light (heat) and the components in the wood react with each other due to the addition of the light (heat). This will happen without the light also, just a lot slower.

One thing is certain: Freshly harvested wood is chemically unstable. Oxidation is one way to describe what is happening during aging, but mostly it is rapid degradation of partially formed cellulose, hemi-cellulose that is being burned up by acidic lignen. When that has happened completely, the remaining acid attacks the complete cellulose but much more slowly. Most of the hemi-cellulose is consumed within 2-5 years. It would not be practical for most builders of wood items to wait for the cellulose reaction to go to equilibrium, as that might take hundreds of years. But it certainly does happen.

Originally Posted by Greg Clinkingbeard

Surely anything that gets molecules moving will cause friction which will, in turn, cause heat. I suspect that any increase in temperature on the bass would be only a fraction of a degree. Have basses in warm climates improved more than those in colder climates?
Oxidation of the wood also chemically changes the wood. How would anyone ever set up an experiment on this?

I don't think most folks that understand thermodynamics would require proof in every individual case. Enough has been proven that most general cases are predictable. Not everything needs to be that well understood to be put to practical use, either. Take for instance the rather complex engineering of the Roman aqueducts that were built long before Isaac Newton accurately described the forces of gravity. The Romans took their observations as practical fact without any "science". And Ken's experience is that older, well played basses generally sound better. He doesn't need an explanation. So his advice to "play the bass" or to "buy an old one" is pretty solid and well founded. It isn't strange to me that his view is perfectly consistent with what thermodynamics would predict.

Originally Posted by Greg Clinkingbeard

I do agree that old wood is harder, on average, than new wood; I suspect it was also harder when it was new. New pine is a crop grown with the intent to maximize yield. I believe that approach produces softer wood.

Hard to say why the older wood is harder as it appears no one was taking very careful notes. In the case of my house, some think that species of pine is extinct. Some think it was the same as Southern Yellow Pine, just old growth and much larger trees than are currently harvested The boards are definitely nice stuff compared to what you see now. In my hall, which is about 15 feet long, there are only two floor boards that do not span the entire 15 feet. Some of them run past the threshold and go into the foyer all the way to the front door, which is another ten feet. Knots in the wood are extremely rare. I have seen old warehouses along the railway here that have 100+ ft. beams in the rafters that are a single tree. Sadly, in the last few years many of these have burned due to arson with no attempt to salvage the pine. There is no doubt that crop pine trees have been bred to grow extremely fast, and this definitely results in more soft grain and weaker wood. But growth rate and hardness tend to be consistently observable only within a given species. For instance I transplanted two very young Tulip (magnolias that are commonly called yellow poplar) trees when these were under 4 feet tall. One of them was only a few inches tall. These were wild trees. Both are approaching 40 feet tall now and it is less than 15 years ago that these were transplanted. These are averaging an increase in trunk diameter of nearly an inch/year. And I'm sure if these were harvested in a few years that the wood would be consistent in hardness and strength to commercially harvested yellow poplar, which is harder and stronger than spruce 2x4's that even when farmed and bred to grow quickly do not grow at the rate of the wild Tulip trees.

Originally Posted by Greg Clinkingbeard

David, are there little insects in your house singing to the studs, causing them to vibrate?

Probably so, but I thought is was just my ears ringing! The wood in my house is so hard that there are places where years ago the termites gave it a go and gave up! Seriously, the colony would find a run of soft grain and last maybe a few feet in one board and then die out. This was probably more than 75 years ago;- before houses were even treated for bugs. And then there were also powder post beetles. I think they gave up too, or the house would be saw dust by now. But I've often wondered if there might be little creatures in the top wood of the basses dancing around when I start playing it. Possibly gnawing a little here and there to improve the carver's work? Well, I kind of hope not... But seriously, this is factual:

Once when I was bowing some really low notes quite loudly, I looked up to find that several spiders, which I had no idea would be disturbed, had crawled out from behind the woodwork apparently to see what all the commotion was! So at least we know that vibrating the wood will drive the spiders out of hiding.