oxalic acid

thinkstoomuchJuly 7, 2010

Hi All,

I've been spending a lot of time prepping a mahogany porch for re-finishing. Part of what I need to take care of is the eight thousand nail stains. Every single nail has a black stain in the wood around it. I have used Restore A Deck. I have also tried oxalic acid according to the directions, twice, and am not much further along than where I started. The directions state to mix the canister (12 oz) per one gallon of hot water. Apply every ten minutes, then triple rinse. While everything is still wet, I feel like the stains are gone. But when things dry out again, there are the black stains. A few of them now have changed from a black stain to more of a yellow stain. ??

So my question is, do I just keep applying again and again? Do I mix a stronger solution? I really don't know, but it sort of feels like with all the rinsing you have to do after applying the acid, you sort of recreate the stains with all the water that is applied. Is that possible?

Any suggestions on where to go from here are greatly appreciated. Also, the only acid I can find is the 12 oz containers at $8.00 a pop. What sort of places would carry this in larger containers? I've gone through quite a few of the 12oz ones and am hoping I don't have to spend that kind of cash again.



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Does sanding not get the rust stains out? Or are they too deep?

    Bookmark   July 7, 2010 at 2:06PM
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I have not tried sanding because many of the nails are level with the surface of the wood. I felt like I would only make my problem worse. I'm thinking that if oxalic isn't working, neither will sanding, but that may be an inappropriate assumption.

As some background, this porch is about 12 years old, and I can almost guarantee that the previous owners did nothing as far as upkeep is concerned from the day they put it in. Before I did the oxalic wash, I stained an inconspicuous board with Penofin, my intended product of choice(I use this on my Ipe deck and really like it.) It was then that the stains really became an issue. I thought that they might blend in with the Penofin. I've found that Penofin on mahogany is much lighter in color than Penofin on Ipe. So, the stains really stand out.

Also, one last question......If I indeed can get these stains out somehow, will they eventually come back? Or will everything be fine as long as there is an appropriate level of upkeep from this point forward?

I'm starting to lose hope that I can make this porch look nice. Any suggestions are very much welcome!


    Bookmark   July 7, 2010 at 4:05PM
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Strange the porch has non galv fasteners.

I buy oxalic by the 50 lb bag its about $50 from a chem store. Keep in mind oxalic is an acid if the fasteners are really non glav further treatment will eat
them up.

I am not understanding the yellow stain part. Anyway oxalic always works that is it does what it does now why the result you are going for is not happening is strange as well. Nails hmmmmmm what kind of nails?? that is do they have a big head showing or are they finish nails with a small head. J.

    Bookmark   July 7, 2010 at 6:17PM
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Thanks for your input John. Much appreciated. The porch installation is much like the rest of the house. You sort of scratch your head and say "Why did they do it like this????" Sigh. I've spent three years remodeling this house, and finally have time to tackle the porch.

Anyhow, the nails appear to be finish nails from a nail gun. I'm assuming that from the stains, they are non galvanized. It had never occured to me that further acid treatment would eat them up. That's why I'm here!

So, would you suggest calling it a day and figure this is as good as it's gonna get? I'm not willing to rip it up and re-do. This porch runs the entire length of the house, so re-do is out of the question. $$

Thanks so much,

    Bookmark   July 7, 2010 at 8:49PM
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You could always pull out the nails, replace them with galvanized screws, sand and stain. Depends on how perfectionist you really are. :-)

Can you post a photo? We might be able to talk you down off the ledge.

    Bookmark   July 8, 2010 at 2:33PM
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Weedyacres........people would definitely call me a perfectionist! But with this 12 year old porch, I'm not willing to pull the nails and replace with screws. Number one, I'm sure there would be too much damage from pulling, and two, I don't want to look at screw heads! And number three, the stains stretch out beyond what would be the screw head. I finished building an ipe deck last summer where I screwed and plugged.........and I LOVE it! It was so worth all those hours of sweat equity. But not willing to do that again unless I'm starting new.

I'll try to get some pictures posted. I've never posted pics, so it might take a few to figure it out!

Maybe there is a stain dark enough to blend the stains? I was hoping to stick with Penofin, but I'm open to any suggestions.


    Bookmark   July 8, 2010 at 4:24PM
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Yo Kim its a good thing they are finish nails.The good news is you can counter sink them. The bad news is you have to countersink them.

Seeing as how you can see the nails its a good bet they are not acid damaged that much and I agree puling nail gun finish nails is not possible. Its time to break out the ol nail punch and the knee pads.

Dont Yell at Me!! I had a hard day!!!

With all the screwing/pluging going on this will be nothing new. Pick out a punch bigger than the nail,how much bigger depends on you. If you want to just countersink the nails and sand the rust off to an area that looks good to you,flood the finish on to cover the nails that would be one way to go so just pick out a punch slightley bigger.

However being the person you are you might want to use a little larger punch,fill the hole with tightbond 111 and sawdust,sand with an 80 grit orbital,do it again and mabey again to get it perfect,and you know who you are,then sand the whole floor. Too much work??? dont even talk to me I just finished hand sanding 300 sq ft of red oak T&G in the living room then hand rubbed watco dainsh oil with two buffing passes.

Anyway they both would work. The idea is to get the nail heads protected from the water.

JonMon very intersted in your choice.

Side Note penofin is junk.

    Bookmark   July 8, 2010 at 7:29PM
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Oh my, JonMon! My knees and back ache just reading your post!! Lol. I will admit though, your suggestion is very tempting. My issue is that I've put in a lot of work so far, and I'd hate to just slap on a finish now and kick myself for not taking the extra step to get the stains completely out. You know? I'd forever look at the stains and be pissed off!

I think what I'll do is try your suggestion on a few inconspicuous boards and see how it goes. Is it possible that the stains could be too deep that even the countersink/sanding plan won't work?

Lastly, I know you're anti-Penofin. I'm willing to give TWP a try if maybe you've got some experience using it on mahogany. Do you have suggestions on what would be nice on this porch? I like the darker, richer tones.

Thanks everyone. I'll try to post pictures this weekend.


PS.....JonMon - does the sawdust necessarily need to be mahogany?

    Bookmark   July 8, 2010 at 9:33PM
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Protected from the water the nails will bleed out a lot less depending on the amount of protection. Using an orbital with a dust colector will be handy they fill up pretty fast. I buzzed out a Makita 5'' on that floor during the weekend so I bought a DeWalt that worked as well any of them with a 3 amp motor will problely do for Ya.

Doing the saw dust thing I get the glue in the hole then spread the dust over it then hit it with the sander. This cloges up the pad pretty fast but it puts a layer of fine dust on. Any dust will do the finish is going to darken it anyway. Just work with it and figure out your own way remember your not killing snakes no reason to rush it.

Penofin is short lived and building coats with it turns into a sticky mess. TWP 116 is a red/brown color.

    Bookmark   July 9, 2010 at 8:16AM
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Thanks John.
I've read your post a few times, and hoping you'll clarify. Are you suggesting this order:
1. Countersink
2. Sand the entire thing until happy
3. Do the glue/dust thing
4. Sand again until acceptable

Or would I countersink, then glue/dust, then sand?


    Bookmark   July 9, 2010 at 9:05AM
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John, I was just reading a different post of yours regarding TWP. You said it requires UV to set up. My porch is a covered porch that gets very little direct sun. Is TWP not a good choice in this location?

    Bookmark   July 9, 2010 at 1:20PM
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Kim you deftenley think too much.

Use the sprit of a sound mind,think like a Country Boy. You got your deck with fasteners that need countersink,so do that. filling the holes,like I am thinking you will,can be done as you go thats the way I would do it that is push in the tightbond111_____ not that much ghesssssssss!!!! the bottle has a slanted tip use it_____ just to fill the void. brush over that hole with sawdust you got from someplace else by hand. Sand this area. As you go the fine dust will stack up in the bag/box dump it in a big bagie and use it as you go.

Its not all that bad just keep going Ya Big Babey!!

Depending on your skill and what you learn as you go it might take two passes but your a pretty smart person so it might not. You got it done all around. Sand the rest of of the deck and keep an eye out for holidays,voids your cant live with,Put The Finish On. Bang Bang done.Your not killing snakes slow down.
The Sun shines every place covered porch is no different. What I was talking bout was a Shop thing,My Shop that has lexann skylights blocking uv all together.

Kim your gender please,if your a girl, I have a Job for You. JonMon www.deckmastersllc.com

    Bookmark   July 9, 2010 at 8:06PM
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Ha ha ha.........you're assuming correct.....all chick here! My daddy taught me all I know, and I'm forever grateful. I've got a sister nearby you, in Tuttle. Next time I visit I'll have to look you up and buy you a beer for all you give to us weekend warriors!

Alright......one last question. I promise. Are you saying that sanding should be done while the glue is wet? Yes? I assume that must push the dust down into the glue? Maybe I'm just having a dumb chick moment........

    Bookmark   July 9, 2010 at 9:35PM
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Why do I work this late???

Kim, learn to work with the orbital sander. There is very little pushing done. Let the machine do the work.

Yes thats the way I do it while its wet although that glue sets up very quickley. After wiping the sawdust in the glue carefully by hand. I put the sander on it.This will add a light coat of dust in your repair combined with the sawdust you wiped on. Reason you wipe the dust on is to soak up some of the glue and save the pad a little guming up.

A case of LoneStar is more like it. J.

    Bookmark   July 9, 2010 at 10:19PM
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Case of LoneStar. I'll remember that........

Thanks for all your help, and patience. Much appreciated. I'll post an update when I've had a chance to give this a whirl.


    Bookmark   July 10, 2010 at 5:28AM
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