Inner culm-wall corrugations - Bundles of fiber/ Phyllostachys aurea

[Mark Meckes]

The surface texture of the inside of dried Phyllostachys aurea here in Texas is highly corrugated ...similar to to the rippled corrugation of cardboard
boxes.
Though most Phyllostachys have some unevenness in the inner culm walls, I'm wondering if the hot, dry summer heat of Texas causes this to be more pronounced?

The last time I worked with P.aurea was in 1985 in Charlotte, North Carolina and I don't remember it being so corrugated, but this might be because I (don't remember), and hadn't worked with many other bamboo species at the time, and hadn't realized that the inner walls of bamboo varies considerably with each species of bamboo.

The P. aurea from Texas had been naturally dried in the grove. The pieces felt light-weight, and when carving the wood, produced a `satin-like' sheen. Some of the bamboo was aged, imparting a brittleness to the wood...as if the central Texas climate had dried out the suppleness of the sugary glues that bind the fibers together.
The water-based `satin' poly-acrylic that I used to finish these small carvings was readily absorbed.
Mark

[Mark Meckes]

Fiber bundles in bamboo are not evenly spaced.
Just as each culm in a grove bears individual characteristics that are determined by species, spacing of culms, growing conditions, and events that occured during it's life, so too are the configurations and characteristics of the fiber bundles which are formed within a bamboo.
These fibers initially develop very early in a culms life - prior to and during the shooting season.
Their function is similar to the structural requirements and sketatol framework of a multi-level sky-scraper.
They require strength as well as elasticity and flexibility, in order to cope with the ravages of climate and weather conditions etc.
The sugars, starches, lignins and moisture content plays an essential role in the development and (re)alignment of the fibers during the emerging life of a culm.
As a culm gets older it contains less moisture content and it's fibers become more `fixed', more resistant to change.
With dried, aged and weathered bamboo, the elasticity of the substances that binds the fibers together becomes more granulated,losing it's holding power, and the fibers which have been bound together in a state of tension let go at their weakest bind, and so a crack forms.
Splitting can be reduced to a minimum through selective harvesting, grading, storing methods, and implementing various processes and techniques during the drying/curing stage.

The following two photos provide a view of the alignment of bundles of fiber as seen fron the inside of a culm of Phyllostachys aurea.
These corrugations (ridges) are more pronounced then with some other Phyllostachys species that I have worked with.
http://www.bamboocraft.net/bamboo/data/503/thumbs/Paurea-192.jpgInner culm-wall corrugations (http://www.bamboocraft.net/bamboo/showphoto.php?photo=2296) - Depicting fiber bundles in
2"(5cm) Diameter Phyllostachys aurea (Austin Texas USA)

http://www.bamboocraft.net/bamboo/data/503/thumbs/Paurea-193.jpg
Inner culm-wall corrugations (http://www.bamboocraft.net/bamboo/showphoto.php?photo=2295) - Closer View

Is this just because of the dry, hot texas summers ( where this material was harvested ) or is this corrugation (ridges) as evident in Phyllostachys aurea in other parts of the world?

~ Mark

[bambooda]

Hello Mark,
Your digital photos are great! Here in Hawaii, P. aurea is one of the prevalent varieties and I use quite a bit of it in my work. Although this is considered the tropics, this temperate climate bamboo seems to thrive here.
I would say the average diameter is around 1-1/2 to 1-3/4 inches, with the occassional 2-1/4 incher.
The ridging on the inside seems to be about the same as your photo with the exception of those growing in very wet areas - which are less pronounced.
The issue of splitting and cracking is a very complicated topic and depends on many conditions (which you've mentioned) including the variety and the environment where culm is harvested.
I have found that some varieties are prone to cracking/splitting as their general nature and others tend to be very stable. I've also found that culms growing near a constant water source are big and vibrant, but weaker (structurally) than culms growing in harsher conditions.

- Cal

[Angel]

Hello Mark and group,
Very very interesting description about cracks and material.
Sometimes, Argentine Ph. aurea shows ridges in the same way as your photo, sometimes connected with septums deformations. But I have no idea about what causes this corrugation.
I've seen this also in Aulonemia from Los Andes, and Bambusa multiplex silverstripe.
Mariana agree with me that well mature culms presents the mentioned ridges.
She reminds me that is a problem to eliminate the paperish material in that culms, to apply enamel finish in bamboo cups.

Angel