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Case Study: Fluxaf Super and Osmo UV oil on oak windows

Traditional Painter Richard Willott spends most of his time hand painting furniture and kitchens in and around Bury St Edmunds but wood finishing work comes in more forms than worktop renovations. This is an extended version of a case study first published in October.

fluxaf super

Sometimes, we don’t always paint wood!

This time last year I was very kindly sent a couple of products to trial, one of them happened to be a small tin of Fluxaf Super. At the time I thought “paint stripping , I haven’t done any of that for years!” The tin was then placed at the back of a shelf for a rainy day.

Then ironically, in the summer I received an enquiry from a potential client who wanted a form of hard wax oil varnish removed from the exterior of their log house! After a site visit and several discussions with Ben at Paints and Interiors, a couple of options were suggested, either sandblasting or stripping.

This particular job came to nothing, but in the meantime an existing client had asked me to try and rescue her windows! Only 2 years prior, she’d had 15 windows and 6 doors beautifully crafted out of solid oak, to which the joinery company had applied a coffee coloured varnish.

exterior oak windows before

The varnish had almost immediately dried out, cracked and started to lift.
Another quick call to Paints and Interiors just to confirm the correct product selection, price and availability, then 2 days later the stripper arrived,

fluxaf super

I then set about restoring the windows and doors to their natural beauty.
After suitable protective sheeting was applied to the areas under the window, a very light abrasion (180 grit) to the offending varnish, and brushed the surface clean. I put on some suitable PPE, then started to apply the Fluxaf Super. It has quite a thixotropic consistency and was very easy to apply and did not want to run straight off the woodwork.

fluxaf super in action

Within minutes the reaction between the stripper and varnish began. I left it for about 30 minutes before taking a small flat bladed scraper, and started to remove the residue of stripped varnish.

The next step was to wash down all of the woodwork with warm soapy water and a green scouring pad. Once washed, the window was left to dry.

oak after Fluxaf super

Once the window frame had dried, I attached a 180 grit Abranet pad to my Festool RTS 400 and lightly sanded the frame, removing any tiny imperfections. The same was done by hand on all of the mouldings and then repeated with 240grit for a smoother finish. I then dusted it down ready for the new protective coating.

oak after sanding

The chosen product to enhance the oak was Osmo UV -Protection oil Extra 420 clear satin- 2 coats.

Application method was going to be the * “FOX” 1" original brush. It has outstanding synthetic bristles which hold volumes of whatever product you chose to use with it. It also has a crisp cutting-in edge straight from the first use.

The Osmo UV Extra oil can protect timber from the greying effect caused by the suns UV rays by a factor of 12. It also offers superb durability with an added biocide to combat insect attack and fungal growth.

Fox paint brush and Osmo oil

The first coat went on like a dream, penetrating into the wood grain, enhancing the natural colour of the oak. This was followed a day later with a very fine rub down with an old piece of 240 grit paper, then dusted down and the 2nd coat was applied.

oiled oak windows

This process resulted in a very happy client, who could not believe how fantastic her windows were now looking. And from a user point of view, it all went according to plan, thanks to the effective thixotropic Fluxaf Super stripper and the Osmo oil, which behaved just as expected.

If you have any questions on any of these products or the process above, please ask. Also @BenSturges is more than au fait with Fluxaf and Osmo, too, and has advised readers to great effect.


Hi, I do have a question!

I went to quote last night for a guy with oak framed exterior windows. I’d like to spec Osmo oil. I asked him what was on them already and he said he thought Teak oil. And, if I can upload a picture or two, you’ll see there is some weathering.

So I’m wondering about the correct work scheme. Fluxaf first, then sand to bright wood? Or the other way round? If Teak oil has been used, can I still use Fluxaf and Osmo? Once prepped, two coats of Osmo and job’s a good un, right?

Also, as this would be a first for me, if anyone has completed similar work, could you give an idea of timescale to complete, say, the window in the top picture. Be generous.

Free advice always gratefully received!

Teak oil is a linseed oil based mix and it looks like it has had its day. I would prepare these windows as in the article.

I can’t tell what is going on exactly in that casement window photo, if it is damage or dirt, but once back to a base, if it is discoloured, you might be looking into oxalic acid to even out the timber.

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Hi Andy,

Sorry, I didn’t get an email notification so didn’t realise you’d replied! I just got off the phone to Richard who mentioned you’d posted.

To my eye it looked more like simple weathering. The house is in a suburban area where there isn’t too much traffic.

Talking with Richard, he recommended cleaning any unaffected areas first (not the grey areas I’d be going to sand anyway) then sanding back to bright wood. He said that as Teak oil doesn’t seem to last long over time, there shouldn’t be a need to go in with a stripper.

Excuse my ignorance here, but what is oxalic acid and how would I decide whether to use it? I’ll have a little research myself, but if you can give some anecdotal advice that might help me.

Thanks for your reply.