A related side note here for the few that will read this at the end of a post:
Wood Expansion / Contraction:
Ever notice how even a barely used hammer head will come loose from the
wood handle?
Most people assume that it is because the hammer has been used a lot and the wood has just worn loose. Not so in all cases because it happens on hammers that have not been used at all. If a hammer is placed in a shop or barn without humidity control - in an environment with lots of seasonal humidity changes, - then over 4 to 5 years, the hammer head can become loose without it ever being used.
The reason is because of contractions / expansion phenomena. With high humidity, the wood expands within the steel head and is very tight. Then at low humidity times, the wood contracts. Again and again this happens. Gradually, the expansion cycle
crushes the cell walls, layer by layer, with each cycle to the point that they cannot and do not recover. Once this starts, the inevitable looseness begins.
Until this is understood, the power of humidity in wood is easily overlooked. In Chris's picts and situation above the obvious strength (or weakness) of CA is displayed. Humidity changes affect most wood in certain directions more than in other directions and it did on this pen. Steel heads and rings (brass too) prevent expansion of shanks but also lead to crushed cell walls. IN the case of CA, - CA nor any finish is a match for the power of humidity in certain situations, unless the finish is flexible.
Another aspect of this is the density and flexibility of specific woods. Some woods can be constrained from expanding and contracting with less force better than others. Some woods that crack easily can be made into veneer as thick as 1/4 inch (6mm) without a problem while others cannot be made any thicker than 1/16 inch (2mm). Why don't veneers contract, expand and or crack like regular wood boards? There is a certain thickness related to individual woods in which treatment with finishes and glues can be effective. In the case of pens, Pen wood thickness is at the approximate level in which wood movement can be arrested - in most cases with the underlying glues and overlaying finishes. But generally, the denser the wood, the harder it is to control or fit the pattern of veneer expansion/contraction control, especially in cross cut woods.
It is my contention that easily cracked hard woods such as ebonies and snakewood will be aided by gluing them to the tubes with a rubber adhesive which will allow for contraction and expansion that CA and Epoxy do not. But for the finish - how do you add a flexible finish?
:wink:
