[Silicone?] Water-repellent surface treatment.

[goodwood]

I attended last week a presentation by a leading purveyor of water-repellent surface treatments developed orginally for preserving stone against the freeze/thaw cycle (think of our historic cathedrals and the like). They have developed a version for wood to, again, prevent the penetration of water into the surface layer.

The presentation by an Industrial Chemist (not just a salesman) was very convincing. It wasn't the sort of stuff I would use on my windows, but I can see that it could well work with stone or brick. Its credentials were certainly impressive, as was its price.

[admin]

The problem with stone and brick treatments is that they stop natural aspiration,in the same way that it happens with wood.

If the material is a simple silicone water-repellent that sits on the surface and lets the brick/stone/wood breathe, then fine, it will work until it weathers away, typically in 2-3 years. But if the material absorbs it and/or too much is applied, it'll start causing problems. In summary it costs a lot to apply, lasts only a short time and can go badly wrong. "The Clerk of The Works" at Salisbury Cathedral spoke about this at great length 20-odd years ago, and his team decided to go without silicone treatments for those reasons. (They were replacing 900-yr old masonry that had weathered.)

[goodwood]

The only thing I can say to that, Philip, is that 20 years is a long time ago. As a woodworker more interested in the latest timber treatments I have absolutely no interest in these people or their products, but it looked pretty convincing to me.

Google "Guard Industries Inc" - and check it out for yourself.

[admin]

Do you have an actual website URL ? I tried googling Guard Industries Inc and found nothing noticeably water-repellent.

[goodwood]

http://www.guardindustry.com/

~k

[Fishrod]

Hi, I have been reading the thread with great interest. There appears to be a great emphasis on using a silicone based repellent. Whilst this will work for a couple of years, given our very abrasive environment the surface treatment soon wears off, and you are back with a porous envelope.

Some years ago this was a great problem within the civils in respect of concrete and spalling especially bridges. Myself and a very good friend were in touch with certain chemists in the USA who had developed a new product that not only prevented the water entering the substrate but also allowed the substrate to breathe. I note that this has been raised by a previous commentator.

This is how it works, the product is not a silicone but a hydrocarbon and relies upon the porosity of the host substrate to draw the hydrocarbon into the substrate. We found a penetration of between 25mm and 35mm to be the measured penetration. This then just sits there a bit like the fabric gortex, whilst rejecting the penetration of water allows the exit of contained water and allows the substrate to breathe.

The UK test bed for this was a house high on Ilkley Moor, Yorkshire, and boy does rain drive up there. The outer skin had become totally porous and ingress of water was prevalent. We applied two coats by spraying (you have to mask up all fenestration and vents), and it worked, nothing has indicated that it is still not working and that is 15 years ago. This has also been applied to York Minster and innumerable bridges up and down the country so it is well proven.

The name of the product is 'Thompson's Water Repellent' distributed now by a very large chemical company and available from any good builders merchants. There are other such products that have come onto the market now, but the key word to look for is 'Hydrocarbon', it is that that does the work.

Rod Appleyard

[admin]

Well I'm blessed. The Thomson's Seal product data sheets do indeed mention hydrocarbons - to be precise, under the data sheet's Composition heading it says :

"A solution of acrylic resins in aromatic hydrocarbon solvents. Contains no added lead."

http://www.thompsonsweatherproofing.co. ... teseal.pdf

And apparently Screwfix sell these products by the can these days.

Well done for updating us Rod

[goodwood]

Hmm, that's varnish dissolved in lead-free petrol. You think I'm joking?

[admin]

Is there anything wrong with varnish + petrol ?

What are the constituents of the Guard Industrie products ? ("ProtectGuard" - which I've heard of, and "Woodguard" which I haven't)

[parougier]

Protectguard's constituents are given by Guard Industrie's website as "Water-borne acrylic copolymer-based", and Woodguard's as "Water-borne fluorinated acrylic copolymer-based"