Author Topic: Removing dark water stains from unfinished wood  (Read 954 times)

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Offline Cheese

  • Posts: 7860
Removing dark water stains from unfinished wood
« on: September 08, 2020, 11:09 PM »
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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Offline DeformedTree

  • Posts: 968
Re: Removing dark water stains from unfinished wood
« Reply #1 on: September 08, 2020, 11:34 PM »
can't help on the stains,  I see you have retractable screens, what are your thoughts on them  yea or nay? 

Offline tjbnwi

  • Posts: 6349
  • Cedar Tucky Indiana
Re: Removing dark water stains from unfinished wood
« Reply #2 on: September 08, 2020, 11:49 PM »
Oxalic acid.

Tom

Offline kevinculle

  • Posts: 380
Re: Removing dark water stains from unfinished wood
« Reply #3 on: September 09, 2020, 08:06 AM »
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.

Offline Gone

  • Posts: 925
Re: Removing dark water stains from unfinished wood
« Reply #4 on: September 09, 2020, 08:56 AM »
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.

Offline Cheese

  • Posts: 7860
Re: Removing dark water stains from unfinished wood
« Reply #5 on: September 09, 2020, 11:29 AM »
@tjbnwi  &  @kevinculle  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.

@kcufstoidi  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] 

@DeformedTree  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.




Offline kevinculle

  • Posts: 380
Re: Removing dark water stains from unfinished wood
« Reply #6 on: September 09, 2020, 12:01 PM »
@Cheese 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.

Offline tjbnwi

  • Posts: 6349
  • Cedar Tucky Indiana
Re: Removing dark water stains from unfinished wood
« Reply #7 on: September 09, 2020, 12:08 PM »
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

Offline Gone

  • Posts: 925
Re: Removing dark water stains from unfinished wood
« Reply #8 on: September 09, 2020, 05:32 PM »
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.







« Last Edit: September 09, 2020, 05:36 PM by kcufstoidi »

Offline Cheese

  • Posts: 7860
Re: Removing dark water stains from unfinished wood
« Reply #9 on: September 09, 2020, 07:48 PM »
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.





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.

Offline johninthecamper

  • Festool Dealer
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  • Posts: 285
Re: Removing dark water stains from unfinished wood
« Reply #10 on: September 09, 2020, 09:16 PM »
I have a can labeled as Conoco radiator flush/soak.another industry to check

Offline kevinculle

  • Posts: 380
Re: Removing dark water stains from unfinished wood
« Reply #11 on: September 10, 2020, 07:40 AM »
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. 

Offline Tim Raleigh

  • Posts: 3585
    • Oakville Cabinetry
Re: Removing dark water stains from unfinished wood
« Reply #12 on: September 14, 2020, 09:45 AM »
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