Using Ronseal High Performance Wood Filler

Am repairing window frames and sills where they have gone rotten with the above excellent product (having already given it a good coat of the Ronseal Wood Hardener) and need some tips on how to work with this filler. Is there any trick to making it spread more evenly and smoothing the surface? The instructions say it can be carved shaped with a modelling knife after 20 minutes, but I imagine that presupposes that one has managed to add the exactly right amount of catalyst for it not to go off quicker or slower, which I have considerable difficulty getting right. Also, there is a piece of window beading which has rotted and affected the wood underneath it. When I replace the beading, I will need to build up the wood underneath it with filler, but presume that the filler will stick to the new beading, so that if I ever have to replace the glass the beading will be firmly attached to the window frame and I will have a devil of a job getting it off. Any tips on how to stop that happening?
TIA
Keith
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It's basically very similar to car body filler which I tend to use for this as it's cheaper - especially in larger amounts. That can be shaped with a variety of tools when hard - files, sandpaper, Sureform etc. As regards the beading if you make good the wood underneath and let the filler harden then shape as needed before fitting the beading, it won't stick to it. However, if you need to fill up to something you don't want it to stick to use some PVC insulating tape.
These fillers ain't as long lasting as cutting out the rot and replacing with new wood - about 5 years seems to be a good life.
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I don't have the expertise to cut out the rot and replacing with new wood myself. We have had a friendly joiner do that at the bottom of door posts etc, but window frames would seem to me to be a lot more fiddly, and therefore presumably a lot more expensive. I assume from what you say that there is no way of shaping the filler before it sets - I don't suppose something as simple as a wet finger would help!
What car body filler do you use?
When you say it only lasts 5 years, what actually happens? Does it just disintegrate and fall out? I presume that at the very least it can't rot, but then if we keep up with proper maintenance of the paint the wood shouldn't rot anyway. We only bought the house 3 years ago, and are discovering that this sort of maintenance was sadly neglected for quite a while before then.
Keith
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A plastic spreader will get it reasonably close - there should be one supplied with the product. But it does sand very easily with a coarse paper. Then use a finer one to get a better surface.

The one my local car paint supplier has on offer - there's not much between them for this sort of use. But only worth doing if you need fairly large quantities like say would fill a 5 litre tin. You could also check Ebay, or a decent local car accessory shop, not Halfords.

The snag is wood tends to expand and contract with the seasons whereas the filler doesn't. So it will eventually come loose. But certainly should last better than ordinary fillers - even those said to be suitable for outside use.
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Dave Plowman (News) wrote:

Dunno if you can still get it, but there used to be a resin stabiliser that soaked into rotten wood and turned it into a completely impervious composite.
Use THAT and THEN body filler..
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I think the OP already has:
"having already given it a good coat of the Ronseal Wood Hardener"
That's the stuff you are talking about IIRC
Darren
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On Jun 4, 2:04pm, dmc@puffin. (D.M.Chapman) wrote:

Many thanks to all for all the useful comments, especially the ones about washing up liquid, and PVC tape.
Keith
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The best solution for that use is slow-cure epoxy resin. It's used by boat builders to saturate wood with resin when making wooden boats. It has low viscosity so that it penetrates wood fibres and when correctly mixed it doesn't go off for at least 24 hours giving it plenty of time to soak in.
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Dave Plowman (News) wrote:

Maybe thats the difference between 2 part wood filler & car body filler?
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The Medway Handyman wrote:

I'm sure they're the same apart from the colour. At least I was told that by some technical bod at Scott Bader a few years back.
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Wood hardener stabilises the wood and acts as a fixer/primer for filler.
As mentioned the problem with fillers is they do not expand/contract at the same rate as wood.
A better solution is to use a flexible epoxy, they have been around for a while but tend to be quite expensive as aimed at the restoration crowd. I recall www.repair-care.com is one, but little mention of it anywhere - the 2pk flexible epoxy is expensive (and it is), but so is the fixer (which looks like a penetrating wood hardener). There may be something equivalent from chandlers re yacht & marine people.
West System may do a flexible epoxy - basically if you modify an epoxy for flexibility you reduce its rigidity in high temperatures & ability to sustain load, however for filling wood this compromise is not particularly material.
Wood hardener acts to reduce the future shrinkage of the rotten wood as it dries once water source removed, it does this quite well and provides a better key for the filler to bind to. Unfortunately it can only do so much and I have had to go back in after a few months to effect a minor repair (joint opens fractionally) but that does hold quite well. I suspect a repeat application of wood hardener by syringe & needle (that will go down well asking at a chemist!!).
Perhaps a combination of cheaper Ronseal hardener with a flexible epoxy? There must be a supplier, not looked, just recall two separate joinery firms reporting the "new" flexible epoxies "solved the long running problem of fillers". I do not believe they are new, I think Akzo Nobel, DuPont, Rogers etc have had such for well over a decade - just not well known.
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js.b1 wrote:

What I've found with sills is there may be an initial shrinkage in the wood as it dries out after being filled. It may be a couple of months before this shows as a hairline crack around the filler but, if that gap is filled, the problem doesn't re-occur.
Car body filler is probably flexible enough to cope with normal movement in wood that is in reasonable condition but, in older houses, the wood is often so porous that it quickly swells by absorbing water.
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That is exactly what I suspect.
Never let relatives "flash the pressure washer" at windows to clear dirt sprayup, the pressure opens any gap between putty & glass right to the wood creating a water pocket. Obviously such cracked putty should be replaced, which is best done as a program of replacement rather than "patch or fix when you find it" :-)
USA do offer flexible epoxy, www.conservepoxy.com/catalog.htm for example although 1/2 gallon quantities are more suited to timber buildings. I have met the old structural epoxy, it makes 50yr old foundation concrete look like Chamberlain.
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I was referring to Ronseal wood filler.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Keefiedee wrote:

Sounds like it would pay you track down a local car finishing trade outlet and invest in a 3.5 kg tin of the cheapest one they do. I was paying about 12 (Bondaglass Easy Sand) until mine closed down. IIRC Halfords are the cheapest for the 1 kg size.
I have body filled sliding sash windows that have lasted 25 years but you need to be ruthless getting rid of the soft, pappy stuff, however deep it goes, and the price of Ronseal doesn't exactly encourage that.
The catalyst is just that. Any amount will make it go off providing it is well mixed (the usual bright red colour makes this easier). Shallower filling goes off more slowly due to less heat being generated.
You have about 5 minutes where you can carve and sculpt quite easily with a scraper, so only mix a golf ball or 2 size at a time if you have any fiddly bits to do. No fingers and no water :-)
Anything smeared with washing up liquid will not stick to the filler, and this makes it possible to get smooth, straight edges by using formers. This might just be a scrap of hardboard pinned to the front of a sill, or something more elaborate. Avoid the need to sand where possible.
Be organised. Have scraps of something to mix on, and ditch them each time. A set of Poundshop paint scrapers is handy. One stays in the main tub so you can dispense the resin without contamination from the catalyst. One does the mixing, and a couple for applying the stuff. When what's left on the mixing scraper is semi hard, use one to clean the other. The residue is now dry enough not to stick to everything but can easily be removed from metal tools.
Not as complicated as it sounds. Honest :-)
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Not quite true for polyester. The "catalyst" is an organic peroxide that gets used up as it promotes setting. Use too little and the filler will never set properly. Use too much and it sets in seconds.
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Steve Firth wrote:

I'm guessing the makers specify more catalyst than is actually necessary, based on the assumption that it won't be properly mixed. On a 3.5 kg tin, I usually end up with a third of the catalyst unused (not by design), and I've never had a mix not set fully. Main thing is, you don't have to be *that* careful with the amounts
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Depending on the size of the gap to be filled, and also whether the gap is simply cosmetic or strucutral I'd use either the normal car body filler which is polyester resin with an inert filler or for the bigger gaps I would use "Bridging Compound" which is glass fibre strands in polyester resin.
Briding compound is much stronger than filler and works about as well as wood. An alternative is to buy liquid polyester resin and to mix in wood as either surform shavings or sawdust. A paste of sawdust + resin is better than most car fillers it has about the same density as wood and when cured can be cut and shaped as Dave Plowman has suggested.
You mention difficulty getting the correct ratio of catalyst to resin. That's not too hard, the rule is a lump of resin about the size of a golf ball to catalyst about the size of a pea.
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%steve%@malloc.co.uk (Steve Firth) wrote:

[snip]
Absolutely spot on!
To add to this though, use a smaller than a pea amount of hardener in this hot weather and slightly more in winter.
Stephen.
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snipped-for-privacy@btinternet.com wrote:

This would appear to contradict Steve's assertion that the resin requires the pea size to cure.
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