Drying Bamboo for Furniture Making

[Capn Bill]

How long does it take to air dry green bamboo, 1 1/2 - 2" diameter before it is suitable for rustic furniture making with a minimal amount of shrinkage after working it? I live in a tropical climate, temps at this time of year in the 80's, with moderate humidity. My bamboo is inside a garage, no air conditioning or anything.

[Mark Meckes]

Hi Capn Bill,
I haven't made any bamboo furniture so I hope others will comment.
It is very difficult to say off-hand how long bamboo takes to dry because of a number of factors involved ...
- Species type ... Different species = different drying rates
- Growing conditions ... Bamboo growing where more moisture is available contains more moisture.
- Time/season of harvest ... Flow of moisture changes with growth cycle and weather conditions.
- Age of bamboo at harvest ... Younger bamboo has a higher moisture content.
- Rate of drying is affected by temperature, humidity and air circulation

I know there are differing philosophies and techniques for furniture making in which some like to prepare certain components in the green stage ...

Firstly there's the technique of lightly heat tempering the bamboo while it is still in the fresh harvested stage. This only removes a small percentage of moisture but can reduce the drying time afterwards.
See this Thread ... Heat Curing / Tempering Bamboo (http://www.bamboocraft.net/forums/showthread.php?t=338)

The other thing is that due to the different density of the outer surface and inner wood, there will be differing shrinkage rates as shown in this pic of a bamboo that had been first heat tempered when green, split then allowed to dry...
http://www.bamboocraft.net/workshop/data/518/thumbs/TorchCured-120.jpg See photo (http://www.bamboocraft.net/workshop/showphoto.php?photo=1262)

Bamboo has different characteristics when heat bending in the green stage, and easier splitting and cutting with knives and chisels when green.
However tight fitting joinery can only be assured when the bamboo is thoroughly dried.

I've been intending to measure some green bamboo, let it dry and check the measurements to see how much shrinkage occurs.

I will guess that there is very little shrinkage lengthwise, fractionally in circumference, but if the outer skin was shaved off, as for tapering pegs for holes, that this part might shrink more ... (?)

~ Mark

[Capn Bill]

Thanks Mark....I will be working with some green bamboo over the next couple of months, and will be able to observe shrinkage in the furniture. I'll report on what I find.

BTW, the strain I am using is:
Dendrocalamus strictus

[Mark Meckes]

Ah yes, Dendrocalamus strictus, I wish I could grow it here but it's a tropical, strong and thick walled ... not sure if this means a longer drying time ... depends ...
I have bamboo stored in the garage too :), and it takes give or take 6-9 months and varies with size and diameter, among other things.
I haven't really taken much notice how long to dry as I have more dried bamboo around then I need.
However I also like working with bamboo in stages from fresh harvested to dry, and after two to 3 months there's no turning back the clock to making them green again.

I can easily to replenish my stock of green bamboo - up to 2 2/4 inches / 6 cm diameter, any time from our Phyllostachys aurea grove...
http://www.bamboocraft.net/bamboo/data/503/thumbs/1P_aurea_1_Austin_TX_USA.jpg See photo (http://www.bamboocraft.net/bamboo/showphoto.php?photo=791)

... but getting larger diameter bamboo requires an annual expedition several hundred miles away to the south/eastern US. We usually go in late winter Feb/March .
These are temperate runners - Phyllostachys species / not tropical clumpers , and because their new shoots emerge in mid-late spring, if the weather is warm, the cut-off stumps already can show signs of rising sap.
See this pic of Phyllostachys edulis (P. pubescens)
Two weeks after cutting...
http://www.bamboocraft.net/bamboo/data/528/thumbs/PedAvLA050225-677.jpg See photo (http://www.bamboocraft.net/bamboo/showphoto.php?photo=2128&cat=528)

Maybe the best time to harvest bamboo is during it's most dormant period which might be in the depths of winter or during the driest time of the year, but this isn't always possible or absolutely necessary.
I've also heard of harvesting mature tropical culms right after their new shoots have reached full height because apparently (??) the sugars have been diverted away from the older culms to new growth (??)

Whichever way, the harvesting time and ensuing the drying climate it will undoubtedly affect the drying rate.

~ Mark