Sap Wood and 'none' sapwood.

[planetWayne]

Hi all,
apologies for the really 'basic' questions here, but I have been reading the thread on the 'cheap english oak' and a question came up about woodworm only being in the sap wood.

I'm assuming that the sap wood is 'just' under the bark on a tree but...

• how deep would sap wood be?
  Why is it not a good idea to use sap wood?
  and lastly - how do you tell where the sap wood ends and the 'good stuff' begins?

Please excuse my complete 'noviceness' on this but I thought I would ask while it was in thought.

Thanks
Wayne.

 

[orangetlh]

Hi wayne, not a basic question at all, in answer to it,

The amount of sapwood in a tree varies from tree to tree, depending on size or age.

sapwood is the living part of the tree structure that transports nutrients and water from the roots making it perfect food for beetles and lavia.

In most timber there is a colour contrast between the sapwood and heartwood which is the good stuff. Sapwood in American black walnut for instance is near enough white. In some timbers like sycamore and maple that are light in colour it is harder to tell, although you should see a slight difference if you look closely.

 

[bjm]

Hi Wayne

If you look at the cross-section of a mature tree, such as oak, you should see a dark inner core (heartwood) surrounded by a lighter ring of wood below the bark. This is the sapwood and as the name implies it is the part of the tree where the sap rises (to the leaves in the canopy). In most trees (but not all) it is generally lighter in colour than the heartwood which contains extractives and other deposits. These extractives are what gives the wood some form of protection against insects and fungi and determines whether a timber is classed as durable or perishable (Oak contains an extractive called tannin which gives the heartwood it's nice colour as well as it's durability). As well as providing protection the extractives can also darken the wood but sometimes this only becomes apparent when the wood dries.

Because extractives are absent in the sapwood it is generally more susceptible to pathogens. The sapwood also contains a higher level of sugars so will be more attractive to anything with an appetite! There is no set measurement of where the sapwood ends and the heartwood begins but the colour change is the best indicator where it occurs.

Once the timber is dry (below 20%mc) both sapwood and heartwood are much less susceptible to attack although some wood boring insects can re-infest dry sapwood. Generally there is nothing wrong with using the sapwood as long as it will remain dry and the use of pieces with sap/heartwood can be a nice design feature!

Brian

 

[Paul Chapman]

In this Walnut log, the dark, central portion is heart wood, the lighter wood around it is sap wood

Here's a log that's been cut

As the tree ages, the sap wood is converted to heart wood, so the proportion of heartwood increases with the age of the tree.

Hope this helps.

Cheers :wink:

Paul

 

[MikeG.]

It is very easy in oak, Wayne. There is a distinct colour difference, and it roughly follows the "wany" edge of the timber, an inch or two wide just under the bark.

You can actually use it sometimes, too (although not if it has woodworm in it!!). You would never use it outdoors, where it simply wouldn't last, but you can use it in places where it doesn't show (inside of panels, underside of tables etc, and where there are no joints). It tends not to be used in areas that are on show, because it just shows up so much with all the darker timbers.

Mike

edit: the other two must have been writing at the same time as me. BJM has it spot on (as does Paul)..........all I would say about Paul's piccies is that Walnut is renowned for having loads of sapwood, and having it in awkward places......as you can see from the photo! Oak has a much, much smaller band of sapwood

 

[Ironballs]

.....and in some species such as American Cherry the sapwood can have such good grain and figure that you may wish to include it in your piece. Ed Sutton had a table in the projects section that had quite a bit of sap in the top. General rule of thumb though is that it's softer, less figured and often full of worm holes; therefore usually avoided

 

[planetWayne]

Hi all,

Thanks for expanding my knowledge on this. Very much well received!

Cheers
Wayne.

 

[matthewwh]

Just a quick note to thank the respondants to this post for their well informed and succinct answers, this is a shining example of UKW at its best.

 

[MikeG.]

Nice of you to say so Matthew!

 

[woodbloke]

I agree with most of the comments on sapwood...I don't use it, ever - Rob

 

[archersam]

guys, thank you for the excellent responses and Wayne thanks for asking the question that I wanted to ask and felt tooooo stoopid to ask ;-)

This forum definetely seems to be one of the better ones that I belong to where asking what you think is a daft question does not get you shot down in flames.

 

[woodbloke]

...where asking what you think is a daft question does not get you shot down in flames.

No such thing as a 'daft' question...just questions :wink: You'll find that we're all willing to help hereabouts, so if you've got anything else that you're unsure about, just fire away - Rob

 

[Ross K]

It's also interesting the huge variance of the thickness of the sap from one hardwood to another.

I use mainly Scottish oak, elm, ash, beech, sycamore and birch and notice in some (eg ash and sycamore) the sapwood is barely discernable with the wood being rock-hard right to the bark. Of this list, oak seems to be the one with the most consistent (typically one to two inch) layer of sap, and as you say it's often riddled with woodworm.

Sometimes they're big'uns - I sometimes work with air dried oak with a draw knife and find myself decapitating some quite big juicy ones...thought I'd share that!! :lol:

 

[woodbloke]

Sometimes they're big'uns - I sometimes work with air dried oak with a draw knife and find myself decapitating some quite big juicy ones...thought I'd share that!! :lol:

Ross - thanks for that ...it's just coming up to lunch time - Rob

 

[Grinding One]

Take a walk in the forrest,see which tree grows the fastest ,that will be the one with the softer wood inside,may also be why it is cheaper too.Hard wood grows at a much slower pace..Plant an Oak a soft maple and a pine tree...do this when your child is born,take him out for a picture every year...I bet the pine out grows him and the maple will be a bit slower,but he will be full grown and that Oak will be a straight little tree yet,maybe 12 ft high.