Old lintel treatment

[Socksitis]

I have exposed some old lintels, they are a little crumbly on the outer wood, but fairly sound within a 1mm or 2mm of the surface. I have read about various treatments from spraying with lime water (I do have some) to injecting with a product to harden the wood, or painting with liquid beeswax. Has anyone tried spraying with the lime water and does it alter the natural colour of the wood. What is considered best? I want the timbers to stay exposed, but to be hardened and not crumble anymore or dust on the surface?

 

[livias]

.....Has anyone tried spraying with the lime water and does it alter the natural colour of the wood.

Yes and No
Works fine for me. You need to spray it several times, one day apart

 

[Socksitis]

Hi Livias, silly question, but it hardened the wood and didn't discolour. Why don't more folks use it then? It sounds ideal.

 

[livias]

Cos there is no one to market it?
Dunno, really. Maybe you should produce and sell it online. I would only demand a 10% commission

 

[Toby Newell]

Why don't more folks use it then? It sounds ideal.

because lime is basic. and basic solutions destroy organic molecules, like lignin.

which is why they make paper by dissolving lignin in a basic solution, to release the cellulose fibres.

so. there may be some weird process by which lime water does in fact harden timber, but from a purely scientific and practical point of view, if we are taking 'lime water' to mean some sort of caustic, basic solution (pH greater than 7) then I would of thought it would have the opposite effect. just saying.

 

[livias]

Well I am no chemist but my unserstanding is
- basic = alkali?
- to destroy anything it has to be liquid. Which it is whan you apply it but it doesnt stay that way for long
- it tends to turn wood to stone. Calcify it

 

[Andys]

Isn't it just depositing a crust of limescale? Maybe there could be an industrial division at Mother Shipton's Cave, hanging up soft timbers for a crusting....

 

[Pennyviz]

Surely the timbers will only crumble from decay, and if decayed then can't stop it apart from maybe using wood hardener to hold it together. If not decayed then a clear wood preserver. I ended up using creosote on my exterior lintel which has stopped the damage being done by gloss paint but obviously a certain thickness was beyond repair.

Penny

 

[Flyfisher]

Isn't it just depositing a crust of limescale?

Yes, a sort of very dilute limewash?

I can imagine such a thing preventing gradual 'spontaneous' crumbling of decayed wood but I can't imagine it would be a particularly strong binder and would likely still crumble if knocked, or perhaps even when being cleaned.

Historically, of course, lime water may have been the best available treatment but personally I'd expect a modern wood hardener to do a far better job.

Why not try both and report back the results after a year or so?

 

[Toby Newell]

^^^ what flyfisher said.

Lime is Calcium Hydroxide = very alkali
(Oven cleaner is Sodium Hydroxide = stronger)
(Potassium Hydroxide = stronger still and used in paper making industry)

Lime is hygroscopic and so will attract moisture from ambient air, this will allow the ions to dissociate and attack the wood.

Its likely in extremis that the physical mechanical bonding of the dried mineral with the wood fibres would have some stabilising effect but chemically it would be slowly weakening and dissolving the timber by dissolving the lignin.

I have zero practical experience with this but can deduce that it's probably not a very good idea in the long term.

I think a modern two part solvent based wood hardener would be much more effective. And as a bonus won't eat the wood it's meant to protect.

 

[Flyfisher]

Another thought is that limewash was widely used on timber framed buildings and still is today, so I doubt it is destructive in the long term. A famous example would be the Guildhall in Lavenham, which is still regularly limewashed these days under the care of the National Trust, who I'd like to think know what's good for such things.
https://www.nationaltrust.org.uk/lavenham-guildhall

The attic timbers in the oldest part of our house (c.1550) are all limewashed and show no signs of deterioration as a result.

Perhaps decayed wood reacts differently with limewash/lime water than solid wood? I don't really know. Either way, I'd still put my money on a modern wood hardener formulations to penetrate and stabilise decayed wood. I know we're all fans of the wonders of lime but let's not forget that historically there was little choice and even less science behind its use.

 

[Toby Newell]

decayed and friable timber has orders of magnitude greater surface area than solid timber and thus the chemical reaction is proportionately less.