When does green wood stop being green?

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pren

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Hi all.

I fancy having a go at some green wood carving having been inspired following a recent trip to Ffrrwm in caerleon, south wales.

I was just wondering how long after felling is wood considered to be 'green'? Is there an ideal level of 'greeness' that is best for carving? I'm probably going to start on some Sycamore.

Thanks in advance. :D
 
When it falls below fibre saturation point (FSP), which is an average of about 30% for most species.

The problem with that pat answer is that wood is never at an equal moisture content throughout its volume except in very unusual circumstances. There is always a moisture gradient.

You could test the wood and find that its moisture content is at FSP, which means the average moisture content is ~30% MC. What you've really got is a part of the wood that's below that figure, and another part that's above it, and maybe there's not even one cell within the structure at exactly 30%. Slainte.
 
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I suppose that coming at it from a green-wood carver's point of view, the reason you want it green in the first place is that it remains easier to cut.

It also depends on the species and what time of year to tree is cut. Oak and Ash for example are quite pliant when fresh but get very hard as they cure.
There tends to be more moisture and sap present in the summer months, which is why wood intended for drying is preferred from the late winter when the sap in down.

So from that angle the answer is when it dries out sufficiently to make your work harder, but it depends on the species of wood and how long you intend working it in the 'green' state.

You can work very quickly or retard the drying process during carving by keeping it covered with plastic. As SD observed, the moisture tends to be unevenly distributed through a fresh cut log, depending on the age and species but be careful with splits and checks as the log carving progresses.

Trunk wood and branch wood can behave differently, too.

Additionally, keep your tools oiled and dry - they will rust like mad!


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Argus":2cdkps0k said:
There tends to be more moisture and sap present in the summer months, which is why wood intended for drying is preferred from the late winter when the sap in down.

Actually Argus, the "sap is down" reason is a bit of a misconception. The moisture content of heartwood xylem doesn't change significantly throughout the year. Sapwood of course carries more water during the growing season than during the dormant period, but even the sapwood still has liquid in it during winter. In some species the liquid in the sapwood rather changes chemical composition during the winter months and takes on some anti-freeze characteristics, eg it may become more sugary thus lowering the freezing point.

The reason for felling, boarding up and beginning the drying process during autumn and winter months, specifically with air drying, is primarily to do with atmospheric relative humidity (RH). Here in the UK, RH hovers around 85% or so during the winter months, and drops to about 65%- 70% during late summer (July- August). There are regional variations to these numbers, but these are fairly typical.

Initial drying during the cooler wetter months generally leads to less drying faults and degrade developing in the wood, eg, surface checking, end splitting, etc, as the loss of moisture from the wood is not so rapid as during the hotter drier months. Slainte.
 
Hi! Thanks for that. really helpful! :D

I'm due to cut down some large overhanging branches in a few weeks, so waiting for the ideal time for cutting isn't practical. The logs will be around 7" thick and a couple of feet long. They will be left in log form for carving.

I'm assuming that the wetter they are, the easier they will be to carve. Similarly, the dryer they get, the finer the surface can be sanded? I think I'll be starting the carving a week or so after felling. There's going to be alot of trial and error here as it's my first forray into green work. I'll artistically butcher it and then see how it sands down after a few weeks/months. Presumably the warmer/dryer the storage area, the quicker the wood will dry?

Apologies for the 'novice' questions . :oops: :D
 
No apologies are required for the "novice question". Everyone has to start somewhere.

Yes, green or wet wood generally cuts more easily than dry wood, and that includes carving.

Similarly, the warmer and dryer are the circumstances that the wood finds itself in, the faster it will dry. However, faster drying also leads to more drying faults, eg, checking, etc. Left in the round your logs will almost certainly form at least one radial split. However, you are planning to carve it wet so splitting will almost certainly happen, but if you are rather inexperienced you will likely to find it quite hard to estimate where the splitting will occur as the wood dries out after carving.

Branches of trees are generally (but not always) of little interest to furniture makers due them being generally full of unstable reaction wood, ie, compression wood and tension wood on the top and bottom side of the branch-- just where these two different wood types dominate in the branch depends on if the tree is a conifer or if it's a hardwood species. However, carvers and turners can often find very good uses for branch wood. Slainte.
 
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