Removing dark water stains from unfinished wood

[Cheese]

A few years back I replaced numerous early 1950's single pane windows in the house with some Marvin thermo-pane casement windows that are aluminum clad on the exterior and Doug fir on the inside.

Unfortunately,  I didn't have the time to properly finish the Doug fir so it remained in the raw state. To add to the anguish, I did such a superior job  [tongue]  [crying]  in sealing up the house when I replaced the windows, that I had an internal high humidity problem that I didn't recognize until a couple of heating seasons went by. At that point however, the damage had been done.

I've since installed a Honeywell whole-house dehumidifier and the moisture problem is gone. However the water stains are still there.

I've thought about bleaching the spots but am open to any suggestion on how to remove the spotting to regain a uniform appearance so that I can properly finish the windows with something clear...painting with a pigmented paint is not a solution unless the pigment is the same as Doug fir.  [big grin]  Any and all suggestions are appreciated.

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[DeformedTree]

can't help on the stains,  I see you have retractable screens, what are your thoughts on them  yea or nay? 

 

[tjbnwi]

Oxalic acid.

Tom

 

[kevinculle]

Oxalic acid is likely the most effective stain treatment, not 100% effective but it should considerably fade the stains.  The challenge will be that oxalic acid needs to be rinsed off thoroughly before finishing and that will be awkward at least for these installed components.  After you get them as clean as possible you may need to broaden your finish options to include ones that can better obscure the remaining residue of the stains.

 

[junk731]

I know you like the looks of the DF but thats not going to happen now.  A good gray toned dye stain would be another potential fix to even out the colour top with an amber toned finished like Target EM2000 Exterior as a topcoat.

 

[Cheese]

[member=4105]tjbnwi[/member]  &  [member=60975]kevinculle[/member]  Thanks, I will try the oxalic acid treatment. Just curious if either of you know what the difference is between a clorox/water solution in a 10%/90% mixture and oxalic acid?

I'm curious because maybe the the clorox/water solution artifacts would be easier to remove from the wood than the oxalic acid artifacts...ie. fewer water rinses may be needed because the clorox solution is already 90% water. If however, the clorox turns the wood white or maybe yellows it, then it's not even a starter for me.

[member=4907]kcufstoidi[/member]  That's an interesting suggestion about using a dye stain and a tinted topcoat. Any suggestions for stain manufacturers?  If I go that way I'd just as soon use something that can be duplicated in quantities, as opposed to using a Transtint solution, as there are 8 windows to do in the loft and then another 13 in the sunroom.

This item has been on my plate for several years now and finally yesterday, I thought that I'd post this question here first before I bit the bullet and had the local SW mix me up some "Douglas Fir" paint/stain.  [tongue] 

[member=68063]DeformedTree[/member]  We absolutely love the retractable screens, they're well worth the expenditure. In Minnesota we have possibly 1 1/2-2 months in the spring and fall when the windows can be opened for "full ventilation" after that it's either heating season or cooling season. So for 8-9 months of the year you're looking through dirty screens that just aren't needed.

We do have cats and previously in the kitchen, screens were always on the windows for ventilation when cooking. Now you simply pull the screen, open the window and the cats can't escape.

Here are a couple of shots of the upstairs, the natural colored windows go well with the rest of the room, thus the reason I really don't want to paint them if I don't have to.

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[kevinculle]

[member=44099]Cheese[/member] oxalic acid is bought as a powder and can be mixed with water to a desired strength level up to saturation, it will not attack or weaken the underlying wood structure but is an effective bleaching agent because the chemical residue remains active on the wood until rinsed.  Household bleach is sodium hypochlorite and the bleaching agent is volatile and less persistent.  I agree with the comments about looking into dye and solid color stains as I expect the best you will be able to achieve with cleaning and bleaching will not be acceptable under a transparent finish.

 

[tjbnwi]

Just rinse the treated area 3 or four times with potable water. Oxilac acid rinses easily.

Make sure you allow the wood to dry completely before moving on the sanding and any type of finish work.

Tom

 

[junk731]

The 2 stains I use all the time are Sherwood Spray Stain, SW BAC Wiping Stain. In spite of the names both are sprayable and wipeable.
Here I can only get the Sherwood Spray Stain from the Industrial division but the BAC is readily available at the SW stores. Both are solvent based stains that you can spray WB as a topcoat after stain has cured. My main WB Topcoat is SW Sayerlack.

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[Cheese]

FWIW...I was cleaning an AllClad stainless pan today with Barkeepers Friend and for some unknown reason I decided to read the contents label.

OXALIC ACID  [eek] [eek] [eek]

So...I decided to make a thick paste with it and I slathered it on the window stain. I let it dry for 2 hours and then removed the paste mixture. Here's a before & after photo.

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So, my task for tomorrow is to locate some oxalic acid locally if possible. I checked today and the local Menards, Home Depot, Lowes, Sherwin Williams, Woodcraft and neighborhood hardware stores did not stock any. There are some more specialty paint stores along with Rockler that I'll contact tomorrow.

 

[johninthecamper]

I have a can labeled as Conoco radiator flush/soak.another industry to check

 

[kevinculle]

Another factor that can help with this cleanup is UV light, when you find your oxalic acid and apply it try to do so when direct sunlight is on the window in question and open the blinds to maximize it. 

 

[tiralie]

So, my task for tomorrow is to locate some oxalic acid locally if possible. I checked today and the local Menards, Home Depot, Lowes, Sherwin Williams, Woodcraft and neighborhood hardware stores did not stock any. There are some more specialty paint stores along with Rockler that I'll contact tomorrow.

Not sure the oxalic acid will do much better than what you have there. There is a two part bleach that you can get at specialty lumber stores and online that may be better.
Good luck. Those stains are difficult to remove.
Tim

 

[Cheese]

I just wanted to wrap this package up so that people have visuals on how well certain things work.

The original water stains on a Marvin unfinished wooden casement window.

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Folks suggested using oxalic acid so while I waited for my package to arrive, I mixed up a thick paste of Barkeepers Friend which happens to contain oxalic acid.

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After the oxalic acid arrived I tried to mix up a thick batch of oxalic acid but it never full dissolved in the water. I heated the water/oxalic acid mixture up and added more acid until it again wouldn't dissolve any more crystals, and then let it cool & thicken. I also added some Barkeepers Friend to thicken it further. You can see in places it's pulling a yellowish/greenish tint out of the wood.

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After many clean water rinses this is the result. It's a lot better than the original photo but it's still not where I wanted to end up.

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I finally tried straight Clorox bleach. A few more rinses and some sanding and I'll be happy with these results.

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[greg mann]

Great thread. I had the same issue but it was in a sunroom that also housed an in the floor hot tub. The condition predated my purchase of the house. At the request of my late wife we removed the hot tub which, for medical reasons she could not use, and set the room up for a nice breakfast room during the warmer months. When my wife passed away I didn’t really use the room and never got around to fixing the discoloration and sealing the wood.

Fast forward a few years and I remarried. As one might guess, new wife desired a hot top so one sits where the other one was, but not in the floor. Discoloration gets worse. I could steam bend wood in that room in create less humidity than a hot tub.

Fast forward a few more years and we are building a new home. Finally addressed the staining as I needed to make the house more presentable for sale. Sanding was my route and it worked pretty well but I think the treatments mentioned here would have been better. I didn’t get around to putting a finish on. The new owner will need to deal with it now, or not.