Wood Preserver - which?

[Matt Green]

And... actually uv light doesnt really knacker wood, trees seem to quite like it.

Trees have bark too.

My old university deptartment did some work on this:

UV pine – the way forward in wood colouring UV pine is jointly funded by the wood industries and the European Union under the CRAFT programme, to the tune of C300,000. It brings together seven companies and three research institutions from Ireland, Germany, Spain and the UK.

The researchers involved from BCUC include Sharon Grover and Prof Hew Reid (Design) and Dr Andy Pitman (Forest Products Research Centre, Technology). The project stems from the desire of the European Union to reduce emission of volatile organic compounds (VOCs) including those used for finishing furniture, since they have a negative impact on the environment. However these finishes serve an important purpose in colouring and protecting the wood surface. Colouring of the wood is particularly important to softwood furniture manufacturers since newly processed softwood is bland in colour and requires staining to meet customer requirements. The scale of the problem can be appreciated when one realises that 70% of EU furniture is manufactured from softwood. In the past, softwood furniture achieved a more agreeable colour on ageing as a result of exposure to light. However, the requirement for rapid throughput in furniture processing means ‘natural ageing’ is not an option. This project therefore aims to achieve accelerated surface colouration through the use of UV light.

One of the partners, Honle, a world leader in UV technology has supplied apparatus emitting a range of UV wavelengths. This will be used to determine the optimum range of wavelengths required to bring about colour change in three softwood species used by EU furniture and flooring makers namely Scots pine (European redwood), pitch pine and radiata pine. BCUC researchers have sourced these species and are currently processing the test samples. Preliminary work has been undertaken to determine the wavelengths and exposure times necessary to bring about the required change. These experiments have shown that the process works and so the project will move on to the next stage, i.e. optimisation. As well as colouring the surface, UV exposure has been reported to harden the wood surface. This is also being investigated at BCUC with the assistance of Dr Hugh Mansfield-Williams of the Forest Products Research Centre. This hardening will lead to the additional benefit of scratch resistance in flooring and furniture, another important property. Although the project is in its early stages, initial results are promising. Dr Pitman reports ‘it is admirable that cross faculty research can be conducted on a problem relevant to all EU furniture manufacturers. Ultimately any process which benefits the environment will be of
benefit to all EU citizens’.

All very admirable stuff, although the reverse is likely to be true in this case, the purpose is to inhibit the impact of UV light on the wood. Seems a reasonable aesthetic concern though.


Matt.

 

[Toby Newell]

Wow! Thanks for that.

So what you are saying Matt that apart from the accelerated catalysation by uv radiation of various chemical reactions that lighten/darken woods (oak, pine darken, rosewood, walnut lighten etc, probably I presume by some compound tannic/wood acid/uv catalysation of the wood fibres in the former and uv photon excitation breaking of chemical bonds of pigments in the latter) uv light actually has a beneficial effect on wood by hardening it. Amazing, see I told you, trees quite like sunlight...

I don't know what point you were making but it was very enlightening.

From a common sense point of view it would seem logical that an organism that formed a thick hard gnarly layer at its outermost edge, which is exposed to uv radiation, would be hardened by it, it's possibly one of the processes involved in bark formation. No, very interesting, you could age softwood, harden and colour it in one process, of course one would have to balance the local reduction in VOC emissions with the increased carbon emissions resulting from the electrical energy required to run the uv lamps.

That does seem a little odd though if that research is current, most odd, are you sure it is not say ten years old? I only ask as these days all the furniture manufacturers and industrial coating manufacturers I speak to are telling me that they use waterborne UV cured finishes with very low or zero VOC'S and have been for many years now. I don't think there is much engineered flooring be it solid, veneer or laminate that is finished with anything but a waterbased UV cured finish (bar speciality oil finishes which are of course not v enviro friendly, not that ppl will listen to me)

Low emissions, wop the uv oven on and ping, ready to recoat in 10mins, looks disgusting mind you and very brittle but there you are, good chemical resistance though.

Ah, found it... Buckinghamshire Chilterns (Poly) University college 2003 "Trials are now underway using this rig to colour scaled down pieces of furniture and
simultaneously cure a specially formulated water-based UV cure lacquer"

And two years earlier...Sonneborn & Rieck Ltd 11 MARCH 2001
"Its second generation of water-based ultra-violet (UV) coatings provides a major advance on anything
currently available. These UV coatings are engineered for modern production set-ups and fully
reclaimable in production use. Pigmented versions have also been developed and a further variation
currently being tested is expected to provide a special and substantial bonus for flush door producers
whose products are delivered for on-site use. These new coatings, which meet severe rating
standards, are designed to meet full European ‘E’ regulations and easily meet the strictest
Environmental Protection Act (EPA) requirements"

Think perhaps your chap was a little bit slow on the uptake.

Did not know about the hardening though.

T

 

[skier-hughes]

Leyland clear woodstain (why they call it that is beyond me) MICROPOROUS i.e. allows wood to breathe so moisture can escape naturally rather than blistering or peeling, think of it as Goretex for wood. Apply 5 coats. Will last 5 years, although you will probably still be coating in five years...

Linseed oil, omg I don't want to go there (just smile sweetly) I could go on...

I don't have much experience of wood preservatives but would presume a clear spray coating of one before the finish goes on would be a highly sensible idea (allow couple of weeks to dry before applying coating and coat pref in warm, at least not wet weather! if poss)
Toby

So, Toby, if you were to build a log cabin you'd coat it with Leylandi clear woodstain, and in your opinion that'd make the log cabin last longest?

Can you expand on the linseed oil bit? I thought it was good for wood?

I'm looking for my log cabin to last the longest possible time, so I don't have to buy another one, so would you use a preservative in this case before the leylandi product?

Maybe I'm calling the product I want by the wrong name, but I see making the log cabin last a long time as "preserving" it

 

[Matt Green]

Wow! Thanks for that.

....

I don't know what point you were making but it was very enlightening.

Only that it does havea non-negligable effect.

Ah, found it... Buckinghamshire Chilterns (Poly)

It's a former Higher Education College, was never a poly.

Recently become a full univerisity and celebrated by closing down its Forest Products dept (that had played a big role in increasing their RAE score, and thus their chances of becoming a full uni...).

Think perhaps your chap was a little bit slow on the uptake.

No, you quoted only part of the issue. The thrust was to create an acccerated aging process that didn't rely on VOCs then develop a product to consistantly stabilise the results.

It was a pretty interesting project though, shame there won't be any more from BCUC.

Cheers,

Matt.

 

[rebeccac]

We are having terrible problems with chestnut window frames and shutters.The frames have had a light coating of a water based impregnating formula.They are beginning to show signs of blackening in some areas and when you wipe your fionger over thesev areas it appears to be resin?

The shutters were painted with a good quality water based acrylic paint but they are discolouring too with 'tea stains ' oozing from joints.

The shutters don't concern me too much as we wanted a 'rustic' appearance to compliement the soft limestone but the windows just look awful.

would it be best to paint the oustside again with the paint we used for the shutters or could the seepage of resin eventually stop?

 

[biffvernon]

I wonder what the 'water based impregnating formula' was?

 

[essexbearhunter]

Rebeccac wrote:

but they are discolouring too with 'tea stains ' oozing from joints.

Has someone been using ferrous fixings e.g. nails, on the joints? This could give a rust mark in a water-based finish ( and eventually a blue/black discolouration of the wood itself due to the woods' acid nature.)

Or could this perhaps be tannin-based ? - The chestnut is a rich source of tannin for leather industries.

 

[middi]

Chestnut exterior joinery wood behaves in a similar manner to oak, unless you "nail" ANY paint and varnishes on the timber it will go dark grey. Both types of timber look better in their natural mellowed state ( I think).