Can wood be preserved underwater?

johndb

I read today that the city of Venice is supported by wooden piles
http://en.wikipedia.org/wiki/Venice#Sinking_of_Venice

The buildings of Venice are constructed on closely spaced wood piles,
which were imported from the mainland. (Under water, in the absence of
oxygen, wood does not decay. It is petrified as a result of the
constant flow of mineral-rich water around and through it, so that it
becomes a stone-like structure.)

I found it surprising and would have thought that wood decays underwater. Even more amazing to realise that Venice has lasted on these for centuries.

I am wondering what conditions are ideal for preserving wood underwater and how strict are these conditions?
After reading a bit more on the web here is what I have learned so far- (maybe some of the things I have read are not all true, nevertheless...).
For wood to decay it needs exposure to water (moisture) and oxygen. If one of these is absent then it doesn't decay .e.g. in the case of underwater wood there is little to no oxygen so it stays preserved.
Underwater logging seems to be an effective way of preserving wood.
http://en.wikipedia.org/wiki/Underwater_logging
http://en.wikipedia.org/wiki/Dry_rot

The perpetual saturation of wood with water inhibits dry rot, as does perpetual dryness.

Coastal piers are other examples of wood in constant contact with water that seems to last a long time.
Note that I do realise that if wood was exposed to wetting then drying then wetting then drying ...etc that it would decay. I'm wondering what happens to wood after long periods of complete submersion underwater.

Questions
Isn't there oxygen underwater? Well of course at least in unpolluted water, this is how fish breathe, so is this oxygen less corrosive for wood?
Is it only possible in mineral rich water like the lagoon of Venice?
Is seawater different?
Does it have to be pre-treated before it can stay preserved underwater?
Experiments I would be curious to know the result of:
If I put a piece of wood in a bucket, put a rock on it to stop it from floating, filled the bucket with water and came back to the bucket in a month's/year’s time, would the wood have decayed?
Similarly if a piece of wooden furniture was anchored to the bottom of the seafloor at a good depth and would it stay preserved?
I am a little confused because a few sources seem to say yes wood can be preserved underwater and others seem to suggest it will decay .e.g.
http://en.wikipedia.org/wiki/Shipwreck#Construction_materials
http://answers.yahoo.com/question/index?qid=20080819044224AAxBdlx

So does anyone here have a view or insight on this topic?
Any good articles or links on the subject would help too.
Thanks

p.s.
I hope this question is on-topic for this forum, if not I was thinking of asking it in the popular science forum but I thought there would be more knowledge on this topic here.
I have only layman’s knowledge about wood, wood preservation and working with wood etc.

William Powell

If your interested in this subject then google elm water pipe

slowburner

Without doubt, the species has a bearing on its ability to resist decay under water. Elm, as WP mentions, has long been known to resist decay under water. I think archaeologists discovered the remains of bridge of Elm submerged at Clonmacnoise on the Shannon, whose condition astounded them. There could be a difference between survival in freshwater v seawater too. I would expect that bacteria, fungi, insects etc. which consume wood in damp open air, would not survive in sea water.
I think I heard that Alder might be resistant under water too. Greenheart was used for the pier stands in Dun Leary.
I knew a Dutch cabinet maker who used to submerge green wood in the mud of a local canal - I never found out what the conclusion of that was but I'm sure the anaerobic conditions limited decay, as they do in bogs. I only know of bog Oak, Pine and Yew but not of Birch, Ash or Willow.
I'm doing the same with some Beech logs in my pond. I've already had some encouraging results with Oak.
I also have vague memories of mention in an old book that fresh sawn planks could be seasoned in two weeks by submerging them in streams. I'll have to look that up.
There are are remains of a petrified forest off Bray - not sure what kind of wood , though.

William Powell

I've certianly read about seasoning wood by putting it in running water in a stream. For some reason I have an idea that was one way that the ash shafts for horse drawn carriges were seasoned another comment on seasoning under water I remember is that it was used for wood that otherwise took a long time to season?

And I always thought it was Alder Piles that were used under Venice, strange wood Alder, out of water its about the least durable timber I can think of.

While saltwater might help prevent timber from decaying wood boring worms start to become a major problem. I collect drift wood for burning and wood turning and the worm holes are sometimes over a cm in diameter.

slowburner

William Powell wrote: »

I've certianly read about seasoning wood by putting it in running water in a stream. For some reason I have an idea that was one way that the ash shafts for horse drawn carriges were seasoned another comment on seasoning under water I remember is that it was used for wood that otherwise took a long time to season?

And I always thought it was Alder Piles that were used under Venice, strange wood Alder, out of water its about the least durable timber I can think of.

While saltwater might help prevent timber from decaying wood boring worms start to become a major problem. I collect drift wood for burning and wood turning and the worm holes are sometimes over a cm in diameter.

I think Alder was known as 'Irish Mahogany' at some point. No idea why - maybe it was ironic.
I won't ask where you pick up the driftwood I'm just curious as to the types you get and if they've been machined or not?;)

William Powell

tbh I get very little true driftwood, we live near a river and everytime there is a good storm it washes all the old bits of timber on the side of the river down on to the beach.

At the same time its a good spot for stuff being washed up and if I wasn't the first on the beach I wouldn't be getting much of it . Most of the true driftwood is pallet quality, do get the odd chunk of something interesting. Nothing really machined except do get the odd bit of "broken boat" but thats quite rare. Have had a few railway sleepers and a massive 2ft diameter telegraph pole last autumn. I've a couple of bits of softwood now that have massive worm holes in them, probably thick fence posts that got washed out to sea and spent a lot of time floating around before getting washed up again.

slowburner

I found a lovely piece of oak driftwood once. I couldn't think what to do with it because pebbles had become lodged in all the usable places and I didn't fancy running it through any machines.
To cut a long story, it turned out that the piece came from a hand hewn pre-historic boat, whose parts are in the process of being re-assembled :eek:

William Powell

slowburner wrote: »

I think Alder was known as 'Irish Mahogany' at some point. No idea why - maybe it was ironic.
...

Forgot to mention almost every tree book I've ever read says that Alder (Alnus Glutinosa) is know in the furniture trade as Irish Mahogany. A couple of googled examples http://www.treecouncil.ie/irishtrees/irishtrees.html and http://www.independent.ie/lifestyle/property-plus/go-to-the-waters-and-the-wild-for-irish-mahogany-125611.html

Now that red coloured heart wood is quite strange as it's actually quite pale when you first cut it and only goes red after being exposed to the air.

slowburner

Thanks WP. I came upon this firm in the U.K. I have never seen Alder for sale but it must be grown commercially there, to supply that firm. The timber looks interesting, a bit like Cherry perhaps. I notice that the panels are made up from fairly small boards. I've never seen an Alder tree more than about 9" thick. I think I heard that it is too fibrous or wooly for turning but if these guys are using it for commercial furniture, it must finish reasonably well.
The Gearagh in Cork is worth a visit if you are interested in Alder in its native habitat. There's a type of woodland there, which I think is unique to Ireland, known as Alder carr.

I'd love to hear your experiences of using it.

slowburner

More here

William Powell

:o:o My main expereince with Alder is as firewood :o:o It grows down our river and every couple of years I take out all the dodgy looking dead/dying ones. I've turned a couple of bowls out of what was probably very green timber and while you get those lovely long wide shavings you get from turning green wood the finish is as you suggest "hairy" but thought that was my turning technique tbh. You're right about the timber looking like Cherry not so much when planked and seasoned but as logs the end grain is very similar.

I used to work in Forestry/Horticulture years ago (my trade really) and you can certainly find Alder up to about 2ft in diameter, have seen bigger but by the time they get to that age they are normally starting to die back all over, not really a long lived species. I did have some seasoned 6 x 1 through and through cut alder boards and the natural colour was superb can't remember what I used them for, probably passed them on to someone with better skill to make use of them - I used to cut a massive amount of firewood and put by anything really good that could be put to better use. I was working on an Estate in the UK during the great storm of 1987 and had quite an interesting log pile back then - wish I still had it :mad:

btw your link should read like this comparing with the pic of the timber I've seen much better colour in alder planks but might be the species. The common Alder here would be Alnus glutinosa which in the timber I've seen is much darker, and I've wondering if the Italian Alder (Alnus cordata) or the Grey Alder (Alnus Incana) are lighter in colour. From the names I'd guess Venice was built on Italian Alder.

Edit> You did the same with the second link, when you cut and paste it make sure you delete the http:// that is already in the pop up dialog for adding a link.

William Powell

@ slowburner the link

http://www.thewoodexplorer.com/maindata/we73.html

is excellent.

It gets the wood colour much better but still not as dark as I've seen and the freshly cut wood is almost red in comparison. Great green on the lathe as you can see it change colour as your turning it.

slowburner

William Powell wrote: »

btw your link should read like this
You did the same with the second link, when you cut and paste it make sure you delete the http:// that is already in the pop up dialog for adding a link.

Appreciate that WP. Glad you managed to decipher the links. I can make very nice shavings, but when it comes to this kind of stuff - I'm a goof

2' wide Alder - wow. You must have got shed loads of Elm back in '87. Bet you wish you had that now.

In relation to what can and can't be turned; I've heard people say that Willow can't be turned for the same hairy reasons. I use it quite a bit and rather like it. I know there are several subspecies but I've yet to find one which doesn't turn with sharp tools.

The Wood explorer database is pure wood porn

William Powell

Most of the Elm was gone by 87, I took hundreds of massive trees down in the North of England in the late 70's when they were all dying, the company I worked for must have felled thousands. Worst thing was we dumped most of the timber :mad:

slowburner

:eek::(:mad: