We have just had a seat carved from an oak tree felled on site. Unfortunately it has brown rot on the seat surface, soft enough to pick out with finger nail. I think there is a "runny" form of polyester resin that is used to fix rot in beams. Can anyone suggest something?
Is there anything inherently more weather proof and UV resistant than ordinary polyester resin for car repairs?
Has anybody any experience of:
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there a cheaper source as I intend to coat the whole exposed surface, there are no holes to fill as yet.
Also and more importantly, polyester is moisture sensitive and presence of moisture can permanently inhibit the cure of polyester, where as the polyurethane based wood hardener is moisture curing.
It's still, at best, only a temporary fix. I fixed a softwood sill by cutting back to good wood and glueing and screwing in new. While painting the whole lot I found some more rot (small) at the other end. I used the Ronseal stuff on it and filled with the Ronseal two-part. The 'proper' repair lasted until I changed the entire window - the Ronseal one fell out after a year or so.
if you look on the site I posted, they've also got something called G4 clear it's used for sealing ponds and marine use, it's UV stable, once the wood hardener has gone off, a coat or 2 of G4 clear and it should be completely weather proof and good for many years.
Lay up resin is not particularly viscous and penetrates rotten wood easily.
It may reduce adhesion and slow the cure, but it doesn't stop it curing.
Moisture curing is the last thing you need for damp wood because it hardens before it's had a chance to penetrate. These products are designed to form a surface coating in cold and wet conditions.
"stuart noble" Lay up resin is not particularly viscous and penetrates rotten wood easily.
Laminating resin is thixotropic and probably a hundred times more viscous than wood hardener
I've known GRP moulds pulled off of damp surfaces that haven't set in weeks because of reticulation. Polyester requires an exothermic reaction to set, and, in the presence of dampness, you need to use a seal between the moisture and resin and the exotherm needs to be greatly accelerated for any chance of getting the polyester to set at all. Have you worked with this stuff? Because I do, Daily.
Moisture curing doesn't mean it goes off on contact with moisture, moisture curing means that moisture is the catalyst and starts the clock ticking, do you think this stuff goes off instantly?
What products? polyester won't go off in cold wet conditions at all unless you kick up the peroxide to around 30% .. and then you have a good chance it will fry in the bowl before you ever get it on, let alone penetrate anything.
Which by the time they're finished isn't going to be a lot different to a Ronseal varnish. The beauty of polyester as a wood hardener is that its volume doesn't decrease because there are no solvents to evaporate. Plus it's less flexible than G4, which is what we're after with a wood hardener.
No, not really. I was just showing off that I knew something about styrene:-) Normally I restrict my advice to things that are easily available. 500ml of fibreglass resin from Halfords etc.
Hang on, it's a long time since I worked seriously with this stuff but isn't there another cold weather catalyst altogether? I can't believe that 30% isn't going to affect the finished article. Do Freemans Distribution still exist? IIRC their catalogue was pretty comprehensive.
I seem to remember testing this when I was using car body filler a lot, and the stuff would set normally between sheets of wet kitchen towel. You could almost use water as a release agent except now and again it would actually stick to a surface that had been wet. That said, the aggregate in filler helps retain the heat and obviously the thinner the layer the longer it takes to cure.
I think the OP probably stopped listening a long time ago. Sensible fellow.
"stuart noble" >dilutents, flow enhancers and anti fungicides.
Heavily thinning it actually makes the polyester, a brittle material, even more brittle. A little flexibility IS what is needed so that it can move a little with the wood. I wouldn't use Ronseal, G4 is vastly superior. Wood hardener has a lower viscosity and will penetrate a lot deeper and it's setting is not dependent on exotherm in the same way as polyester.
If you need to know where to buy it in future ... to avoid the substantial mark up that Halfords put on what, I consider, is a very inferior laminating resin ... let me know ;-)
Not exactly....... you still use peroxide, you just have to increase the Cobalt because it's the mix of Cobalt and peroxide that cause the exothermic reaction that gets the resin to set. Cobalt and Peroxide are highly volatile in close proximity to each other, even the fumes mixing can be explosive. Atmospheric temperature doesn't affect polyester as much as direct contact with moisture. Yes, 30% will greatly affect the quality of the resin. but what affects it most is the reaction of heat and not the quantity itself, cooked resin is very brittle. When dealing with moist surfaces, in thin layers, we only do this on the surface coat, because we are trying to counteract the retarding effect of the moisture, the moisture retards it and stops it cooking so it doesn't get brittle, it has to be done quick or it will fry in the bowl before you've finished and it takes a lot of experience to be able to take all the environmental influences in to consideration and get the timing right (I know 1 or 2 mould makers that keep journals that take in to consideration atmospheric moisture, but I find that a bit anal and go by the seat of my pants ;-) ..). Too slow and you're doomed to be sitting there with a heat gun for an hour, too fast and it's gone off in the bowl before you've finished, it's a very fine tolerance.
Here, this depends on volume and mass, if you have enough mass, then the exotherm can take place. Mass has a huge effect on the setting time of polyester, it doesn't affect PU or Epoxy to the same extent. In the small amounts that we are talking about in terms of sitting in the pores of the wood, there wouldn't be enough mass for the exotherm to take place in a damp environment. An Example would be in something i did recently. I used tinted polyester as a surface coat on some MDF furniture to make a tough scratch resistant coating, this was made during the summer, on dry MDF, only the inherent moisture that resides in the MDF naturally. I wanted it to set reasonably fast so I went with about 10% peroxide. The stuff in the bowl went off in 10 minutes, the coating on the MDF was still sticky after 24 hours, purely because of the intrinsic moisture in MDF and the thin section of the coating. It took 72 hours before all traces of stickiness had vanished. With body filler you retain the mass to cause the exotherm. The exotherm on the MDF was extremely retarded by the thin section and moisture. But try it yourself as an experiment, buy some laminating resin, mix as per instructions and paint a thin layer on some MDF and compare setting time to the stuff in the pot. I would think you'll find, that if you followed the mixing instructions, the stuff in the pot would have gone off within 20 minutes and the MDF would still be sticky this time next week. In fact, you can see the difference purely in mass. You could fill a cup with resin, and fill another cup an 1/8th full, and the full cup will likely boil long before the 1/8th of a cup has gone beyond the gelling point. In mass, Polyester will go off underwater, the surface will remain sticky and won't adhere to anything, but the body of the polyester will set, in fact, we use a bucket of water, to discard any excess polyester, because if it's left in the mixing bowl, it will start to fry in thicknesses above half an inch, the water retards the resin and stops it frying. Frying resin turns all the styrene to gas and can be rather noxious.
Except that the type of wood this is normally used on would have given up natural movement many moons ago. It can swell if it gets water logged but the ambient expansion/contraction thing doesn't happen because it has technically ceased to be wood.
I used to buy from a local GRP factory where they made incredibly large moulds in primitive conditions. It was the size of an aircraft hanger with water running down the walls, windows missing etc. I suppose that's what convinced me that anything was possible with the right chemistry.
I think maybe they use a different resin for filler because it's very effective as a "skim" on sills etc. It certainly cures much faster than laminating, even in thin layers.
Again, I think a different type of polyester may have behaved better. Scott Bader used to do various resins for different applications. I can't believe there would be sufficient moisture in mdf.
Don't they add wax to help prevent surface tack? IIRC the idea is that the wax forms a film on top of the curing resin and supposedly keeps it warm. Dunno, it was a long time ago when I faffed about with all this.
Even Kiln dried pressure treated and aged wood needs aclimatising ......... there'll still be some movement ... and a brittle polyester with a weak matrix would crack up after time and surface would go like crazy paving ... once it's stabilised .. then the movement will be more controlled ... people stabilise bog oak, mammoth tusk and god knows what else for making custom knife handles, all because there is still some chance of movement and to control deterioraton. (I was a joiner for 10 years before moving to what I do now, so i know wood too .. ;-).. )
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There is .. the right Chemistry is PU ;-) ..at least for the OP ... because he don't want to be messing around with highly volatile chemicals at home.
They probably do
Yep, Scott Bader and Norpol are the 2 major PE Resin manufacturers that i use (I prefer Norpol)... and they do supply different qualities of resins ... but it all still boils down to polyester, which for some tasks is an unsuitable resin due to it's brittle nature, dislike of moisture and exotherm and mass dependent setting. Casting polyester has a much lower viscosity than laminating polyester, but I still wouldn't use it for this purpose, for the reasons of exotherm retardation.. ... If you don't believe me ..... and I was a little surprised too ... and i use this stuff regularly ..... try it! .....
Most good quality laminating resins already have Wax in them .. and you can add more wax if required ... but this wasn't just a tacky surface ..... this was still sticky resin .. you could still push a fingerprint in it after a day
Ah, a jack of all trades eh? ....:-) Seriously though, what I find with polyester filler on rotten windows is that after a couple of months the wood dries out to the inside of the house, whereupon it shrinks to give a crack round the filled area. But, once this is filled, there is no further movement. This is what leads me to believe that relative humidity doesn't really affect old wood. I have a front door that swells every time we get heavy rain because it physically absorbs water, but my Victorian interior doors don't move at all (they're still as pissed as they were 20 years ago after the central heating was installed).
I believe you, I really do :-) I remember Bondaglass selling those castings of a tin of beans, half poured out, with the falling beans frozen in time. I think they were fashionable for five minutes in the 70s. Still not sure how they did that but I reckon you might be about to tell me :-) When all's said and done, it's difficult to tell whether resin that's disappeared into wood has cured properly or not. I recently advised someone on here to use the Halfords resin, and he replied and said it had done a grand job, he'd re-painted the windows, and everything was hunky dory ....... only he decided after all not to use the hardener.
"stuart noble" that swells every time we get heavy rain because it physically absorbs
But the central heating caused the old doors to move when it was installed? ... so imagine an old piece of wood that was sealed and then exposed to just about the driest year we have ever had, like this year.
Yep ..... seen them ... made some similar things for commercials and stills advertising. The beans were cast seperately, and then mixed in to the sauce resin and filled a mould of a sculpt to look like it was poured from a can ..... and everyone thinks "how did they get it to go off as it was poured?" :-O ;-)
Hmmmmmmm ??? ... the intention is to stablise the wood so it NEEDS to go off in the wood otherwise it isn't stable... if I am doing small parts i will also pull a vacuum on the wood with it sitting in some resin
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