I've been to look at a property today that has oak windows and external doors. They were all treated with Osmo oil when installed around 5 years ago. Without going into too much detail, I'm presented with woodwork that has some fairly ingrained mould/discolouration and some of it is pretty deep. Basically, in my opinion the client was poorly advised and the wrong product was applied for the location and usage of the property. But that's largely by the by. Whatever I do from here I'm obviously going to have to strip the oil and treat the mould before I start to think about applying a new finish. This is a new task for me, so when it comes to stripping the oil prior to mould treatment and any necessary sanding...chemical stripper? Thinners? Or just go straight into the sanding?
Before you go mad stripping doors, the ingrain mould might just be dirt from grubby mitts,etc, & you might fix a wax cleaner like Osmo Liquid Wax Cleaner, (might need a soft nail brush to help), will restore the doors, then refinish with two coats of Osmo UV Protection Oil Extra. Can always contact Osmo for advice with regards to other suitable cleaners. http://www.wood-finishes-direct.com/product/osmo-liquid-wax-cleaner?gclid=COez1eC-0NICFXIW0wodzfgAGA http://www.osmouk.com/contactus.cfm
Also check the door is solid oak and not a veneer, I have used a wood bleach to clean up the mould staining with success (test area advised).
Thanks chaps, they're solid oak and the mould staining is definitely down in the grain. It'd be great if it was just surface muck. It's even got under seals in places. Most of the horizontal surfaces are pretty bad with deep staining so the oil is going to have to come off on those even if the client opts for a re-oil. Astra, when you bleached how did you go about removing the oil to get at the wood?
I didn't as the door was varnished. After 5 years the oil will have dried hard so probably will sand back ok. To be fair though whatever product you use it will degrade over time and the mould will return.
Ah right. Yes, the oil has gone pretty darn hard. What you mention there is the problem. It was applied and then forgotten about for a few years. It wasn't maintained at all until I think it was last year that the chap who does the gardening had a go at sorting it out. With this in mind and looking forward, I'm thinking of oil based Weathershielding the wood after treatment. Even though it's a shame to lose the natural look. There's not one other property in that area that has the oiled natural finish. They are all either upvc or painted...
The main question is what is the finish they want? Oak has been used for centuries in house and boat building without any top coat applied the only aspect is that it will go "silvered" which some people like others prefer a more "wooden" colour. There are many products available oil, oil and varnish combined, varnish, shellac, epoxy and varnish. A wide range of these are available in boat yards and ships chandlers. If they can last years of being exposed to sea wind, air and salt, they should last a good decade on a domestic building. They will also have a good range of products to remove any algae without any bleaching or destroying the fibres.
Mold was in mentioned in the original post. Mold will typically grow where its damp and warm, typically not on external wood surfaces exposed to the air. A cleaning solution for algae will kill both mold and a penetrate deeper to kill of any roots that may be present for an algal infection
Thats the trouble with oak, if it gets repeatedly wet it will go black, in grained dirt will obviously go dark as well. Algae can easily be confused with mold - we have seen this sort of thing many times on window frames and other pieces of timber. . This is going to be a killer of a job sanding down the frames and door, especially in this weather and it isn't going to be cheap. Its probably going to work out at 3 days an item between sanding, making good, two or three coats of finish. Probably £2,000 worth of work if not more. As you say a bleach could kill it but a propriety product may be better. so I would go for some specialist products to make sure the job lasts
I was referring to a Wood Bleach such as sold by 'Liberon' not to kill the mould but to remove the discolouration. Works well and have used in on several so called hardwood doors in the past.
I think there's a combination of the oak blackening sospan describes and mould. So, this is what I'm currently thinking based on what you chaps have said and a little research of my own. To remedy the issues and restore an oiled finish: Sand back all the affected areas to remove the Osmo. (No need for chemical strip as it's aged and hard) Treat with a fungicidal wash. Treat any blackened areas with wood bleach/oxalic acid. (Liberon does get very good reviews) Rinse thoroughly. Apply a neutralising alkili solution and rinse thoroughly again. Let it all dry thoroughly then do a final sand where needed. Apply Osmo UV protection oil. Inspect and maintain on an at least annual basis. With localised application of the wood bleach I can imagine that there may well end up being variation in finish colour so would I be right in thinking it's best to do everything? To remedy the issue and go to a painted finish: Do all of the stages up to "final sand where needed" Apply the oil based weathershield system. One way or another, sospan is right, this is going to be a lot of work. It's a fairly big house too...
Very tedious as well. Battling the weather is going to be an issue - prepping the frames and then it rains, could be a few days before you can get any treatment on them.
Yup. Luckily the client doesn't need it done in a block and I can work it around other work and the weather. It will have to be a case of working on maybe one or two frames at a time
Any thoughts on this bit? "With localised application of the wood bleach I can imagine that there may well end up being variation in finish colour so would I be right in thinking it's best to do everything?"