Sealing wood.

[David Paste]

If you completely sealed a plank of dry wood, say in oil paint or smothered
it in rubber cement (I'm assuming oil paint dries to a gas-prof finish), would
the wood actually be preserved, or would it eventually rot anyway?

Thanks in advance.

[Martin Brown]

Even "dry" wood isn't all that dry.

Many paints have pinhole defects. Some of the oil based aluminium
primers come close to the ideal waterproof and gas tight seal.

Indoors wood lasts almost forever if you keep it dry. Outdoors and/or in
contact with soil something will rot it away no matter how much CCA you
dose it with. Impervious finishes have a nasty habit of falling off.

Usually wood rots from the end grain and knots so pay particular
attention to those if you are putting something in to last.

--
Regards,
Martin Brown

[David Paste]

On Thursday, 7 April 2022 at 17:57:20 UTC+1, Martin Brown wrote:

> Many paints have pinhole defects. Some of the oil based aluminium
> primers come close to the ideal waterproof and gas tight seal.
>
> Indoors wood lasts almost forever if you keep it dry. Outdoors and/or in
> contact with soil something will rot it away no matter how much CCA you
> dose it with. Impervious finishes have a nasty habit of falling off.
>
> Usually wood rots from the end grain and knots so pay particular
> attention to those if you are putting something in to last.

Thanks, Martin. Do you have any experience with Accoya?

[Theo]

Wood changes shape with temperature (and humidity). Many paint finishes
aren't flexible enough to accommodate the changes. If the coating was able
to exclude all oxygen then it wouldn't rot (eg ship timbers found in seabed
mud) but many paints aren't sufficiently flexible and would crack, letting
humidity and oxygen in.

Theo

[Martin Brown]

None. If I want a nearly indestructible hardwood for outdoors then I
would probably go for opepe used for dyestuffs filters and waterways.

https://www.wood-database.com/opepe/

My dad used to get the offcuts and we made fences from them in the 70's.
They were still standing with no maintenance over 50 years later...

You pretty much have to use metalworking practices on it drill and
screw. Very hard brittle as hell and shatters if you try to nail it.

The fresh wood is a rather wonderful orange not done justice by the
online database. It weathers to a silvery grey. There is almost nothing
in the UK that can touch it.

There is always a price to be paid for near indestructibility. In this
instance it is that you have to be very careful how you use it.

Depending on where you are in the UK there are a few decent timber
dealers about who still know their stuff and have unusual hardwoods.

--
Regards,
Martin Brown

[Jeff Layman]

If appearance isn't too much of an issue, old sleepers could be
considered, such as at
<https://www.uksleepers.co.uk/product/Untreated_Reclaimed_Tropical_Azobe_Hardwood_Sleepers>

Also see "Untreated reclaimed Jarrah A Grade sleeper" at
<https://www.railwaysleepers.net/reclaimed-railway-sleeper/>

Note, however, that jarrah is extremely hard and is said to blunt saws
very quickly. TCT blades are recommended. It is a very nice wood, so if
you've got a spare half-hour you could make something like this:
<http://news.baileyguitars.co.uk/index.php/2014/11/baritone-uke-jarrah/#jp-carousel-10651>

--

Jeff

[The Natural Philosopher]

On 07/04/2022 17:34, David Paste wrote:

It should in theory be preserved.

--
Socialism is the philosophy of failure, the creed of ignorance and the
gospel of envy.

Its inherent virtue is the equal sharing of misery.

Winston Churchill

[The Natural Philosopher]

best answer yet +1

[rick]

On 07/04/2022 17:34, David Paste wrote:

If it were fully dry and totally encapsulated it would not rot, but
either is difficult to ensure.

[Andrew]

On 07/04/2022 18:50, Theo wrote:

The (iron) hull of the SS Great Britain started to disintegrate when it
was brought back from the Falklands to Bristol so now it is
in a dry dock with a glass roof to simulate the water level and
underneath it is permanently heated and dried, courtesy of RTZ,
or Rio, now that the 'Zinc' seems to have been dropped.

God knows what the annual energy bill is for that.

Hasn't the Cutty Sark been given the same arrangement ?

[TimW]

On 07/04/2022 17:34, David Paste wrote:

Rot is a fungal decay that requires both damp and air.

So wooden objects are preserved in the dry desert since ancient egyptian
time, they can also be preserved underwater, especially in certain types
of mud which prevent oxidation, or pickled in acid bogs which prevent
fungal decay. People often observe that boats left afloat rot above the
waterline (rainwater and air) quicker than below the waterline (not much
air).

So yes, if you could seal a piece of wood well enough (which would be
hard) you would keep out the air and the damp and it would never rot.

TW

[David Paste]

On Thursday, 7 April 2022 at 18:50:41 UTC+1, Theo wrote:

> If the coating was able
> to exclude all oxygen then it wouldn't rot (eg ship timbers found in seabed
> mud)

Oh yeah, I didn't think about that, or peat bogs, etc. Thanks!

[David Paste]

On Thursday, 7 April 2022 at 19:35:20 UTC+1, Martin Brown wrote:

> https://www.wood-database.com/opepe/
>
> My dad used to get the offcuts and we made fences from them in the 70's.
> They were still standing with no maintenance over 50 years later...

Thanks Martin, that's really interesting. Do you recall is it was a
particularly oily wood when you got hold of it?

[David Paste]

On Friday, 8 April 2022 at 08:48:58 UTC+1, Jeff Layman wrote:

>
> Also see "Untreated reclaimed Jarrah A Grade sleeper" at
> <https://www.railwaysleepers.net/reclaimed-railway-sleeper/>

Thanks!

> Note, however, that jarrah is extremely hard and is said to blunt saws
> very quickly. TCT blades are recommended. It is a very nice wood, so if
> you've got a spare half-hour you could make something like this:
> <http://news.baileyguitars.co.uk/index.php/2014/11/baritone-uke-jarrah/#jp-carousel-10651>

Ah yeah, did one of those this mornng.

[Martin Brown]

It is a bit nasty to work with. Hard brittle and splinters easily but
not actually oily. Fresh cut it is a wonderful shade of orange.

My recollection is that it would take oil based varnish OK but would
happily survive outdoors almost indefinitely without any treatment. No
experience og it with modern water borne formulations.

Being in direct contact with wet soil will do for it eventually but we
are talking several decades. A decent wood merchant will have samples.

Do check that you can work with it before bulk buying. It is closer to
metal working than woodwork because it is so brittle. Nailing is out.

--
Regards,
Martin Brown

[David Paste]

On Wednesday, 13 April 2022 at 17:16:15 UTC+1, Martin Brown wrote:

> Do check that you can work with it before bulk buying. It is closer to
> metal working than woodwork because it is so brittle. Nailing is out.

Such a vulgar activity anyway... ;)