Dining room floor is red oak with polyurethane finish. A plastic bag
with some dishes sat in one place for a couple of weeks - when I
removed it there was a dark blue/green/black stain.
The stain is in the wood. Tried scraping, but it apparently goes
deeper than I'd prefer to scrape. Used a hot oxalic acid solution on
it a couple of times, but doesn't make much difference. I tried it
after the wood was scraped, so it very definitely penetrated.
It looks like an iron stain, but the oxalic acid usually bleaches
those very well. All I can think of is that maybe one of the dogs
urinated on the bag while it was sitting there, but that's just a
guess.
Has anyone found that the two-part bleaches, or anything else, work
when oxalic acid won't?
John Martin
Hi John,
Were you successful in removing the stain? If so, could you post how
you removed it? Thanks.
Andy Tenka
On Jan 31, 10:52=A0pm, John Martin <[email protected]> wrote:
> Dining room floor is red oak with polyurethane finish. =A0A plastic bag
> with some dishes sat in one place for a couple of weeks - when I
> removed it there was a dark blue/green/black stain.
>
> The stain is in the wood. =A0Tried scraping, but it apparently goes
> deeper than I'd prefer to scrape. =A0Used a hot oxalic acid solution on
> it a couple of times, but doesn't make much difference. =A0I tried it
> after the wood was scraped, so it very definitely penetrated.
>
> It looks like an iron stain, but the oxalic acid usually bleaches
> those very well. =A0All I can think of is that maybe one of the dogs
> urinated on the bag while it was sitting there, but that's just a
> guess.
>
> Has anyone found that the two-part bleaches, or anything else, work
> when oxalic acid won't?
>
> John Martin
On Feb 15, 1:09=A0pm, [email protected] wrote:
> Hi John,
>
> Were you successful in removing the stain? =A0If so, could you post how
> you removed it? =A0Thanks.
>
> Andy Tenka
>
> On Jan 31, 10:52=A0pm, John Martin <[email protected]> wrote:
>
>
>
> > Dining room floor is red oak with polyurethane finish. =A0A plastic bag
> > with some dishes sat in one place for a couple of weeks - when I
> > removed it there was a dark blue/green/black stain.
>
> > The stain is in the wood. =A0Tried scraping, but it apparently goes
> > deeper than I'd prefer to scrape. =A0Used a hot oxalic acid solution on
> > it a couple of times, but doesn't make much difference. =A0I tried it
> > after the wood was scraped, so it very definitely penetrated.
>
> > It looks like an iron stain, but the oxalic acid usually bleaches
> > those very well. =A0All I can think of is that maybe one of the dogs
> > urinated on the bag while it was sitting there, but that's just a
> > guess.
>
> > Has anyone found that the two-part bleaches, or anything else, work
> > when oxalic acid won't?
>
> > John Martin- Hide quoted text -
No success yet.
First try was the oxalic acid. Hot, saturated solution. Scraped
through the finish and well into the wood, and flooded on the oxalic
acid solution several times. Some small improvement, but it may have
been due more to the scraping and some dissolving of the stain than
any chemical action. I've used oxalic acid many times before and know
that it usually works quite well.
Second try was with some 12% sodium hypochlorite (pool shocking
solution). This is about twice as strong as regular laundry bleach.
It may have lightened the stain very slightly, as with the oxalic
acid, but if it did it was probably due more to dissolving the stain
than to chemical action.
I may try the opposite tack next - a reducing agent such as sodium
hyposulfite. Maybe lye or hydrochloric acid. Or maybe a two-part
wood bleach. Something has to work, and I really don't want to scrape
any deeper than I already have.
I'll post results when I have trhem.
John Martin
On Feb 4, 11:11=A0am, John Martin <[email protected]> wrote:
> I scraped down through the finish before using the oxalic acid the
> first time. =A0Have used it probably three times, and each time it was a
> hot solution as saturated as it would get.
That may be a problem; oxalic acid is unstable, it wants to
stay cold (and of course, you have to handle it with
glass or plastic, it gets poisoned in a steel or stainless
container).
It makes iron stains go away by dissolving the iron, but you
want to rinse away the solution or the iron comes back
again when the oxalate destabilizes.
Rather than scraping, I'd use a chemical stripper.
It's much easier, and finish penetration might defeat scraping.
On Feb 3, 3:39=A0pm, "Baron" <[email protected]> wrote:
> "John Martin" <[email protected]> wrote in message
>
> news:[email protected]...
>
>
>
>
>
> > Dining room floor is red oak with polyurethane finish. =A0A plastic bag
> > with some dishes sat in one place for a couple of weeks - when I
> > removed it there was a dark blue/green/black stain.
>
> > The stain is in the wood. =A0Tried scraping, but it apparently goes
> > deeper than I'd prefer to scrape. =A0Used a hot oxalic acid solution on
> > it a couple of times, but doesn't make much difference. =A0I tried it
> > after the wood was scraped, so it very definitely penetrated.
>
> > It looks like an iron stain, but the oxalic acid usually bleaches
> > those very well. =A0All I can think of is that maybe one of the dogs
> > urinated on the bag while it was sitting there, but that's just a
> > guess.
>
> > Has anyone found that the two-part bleaches, or anything else, work
> > when oxalic acid won't?
>
> > John Martin
>
> Hello,
>
> =A0 =A0 I would take another shot at Oxalic Acid. =A0It sounds as though =
you are
> going to have to strip the finish off of the stain before going at it aga=
in.
> Make sure the Oxalic Acid solution is saturated and let it sit until dry.
> You will have to wipe up the resulting dried crystals with a damp cloth. =
=A0Do
> NOT brush it up. =A0It will have you sneezing your brains out if you swee=
p it.
> Also, do not let the dog anywhere near the spot when it is being treated.
> Oxalic Acid is quite toxic.
>
> =A0 =A0 If you can manage it, try to have sunlight hit the spot while it =
is
> being treated with Oxalic Acid. =A0The sunlight will help bleach the stai=
n.
>
> =A0 =A0 I would try hypochlorite bleach if the second treatment with Oxal=
ic Acid
> did not work. =A0I have used swimming pool hypochlorite instead of "Cloro=
x"
> since you can make it up to be a stronger solution.
> =A0 =A0 I would move onto the two-part wood bleach, caustic and Hydrogen
> Peroxide, as a last resort.
> =A0 =A0 Once you get the stain out, I bet you will have to recolor the ar=
ea and
> then spot finish it. =A0This will not be fun.
>
> Good Luck.- Hide quoted text -
>
> - Show quoted text -
Thanks, Baron.
I scraped down through the finish before using the oxalic acid the
first time. Have used it probably three times, and each time it was a
hot solution as saturated as it would get. I've used it before, and
know that it usually removes everything rather quickly. On this stain
it has removed a bit of it, but I couldn't say that it wasn't due more
to the scraping and some dissolution of the color than to a chemical
bleaching.
I do expect that I'll have to add some color afterward. Anything
would be better than it is now, however.
I'll try the hypochlorite and peroxide bleaches next.
John Martin
"John Martin" <[email protected]> wrote in message
news:[email protected]...
> Dining room floor is red oak with polyurethane finish. A plastic bag
> with some dishes sat in one place for a couple of weeks - when I
> removed it there was a dark blue/green/black stain.
>
> The stain is in the wood. Tried scraping, but it apparently goes
> deeper than I'd prefer to scrape. Used a hot oxalic acid solution on
> it a couple of times, but doesn't make much difference. I tried it
> after the wood was scraped, so it very definitely penetrated.
>
> It looks like an iron stain, but the oxalic acid usually bleaches
> those very well. All I can think of is that maybe one of the dogs
> urinated on the bag while it was sitting there, but that's just a
> guess.
>
> Has anyone found that the two-part bleaches, or anything else, work
> when oxalic acid won't?
>
> John Martin
Hello,
I would take another shot at Oxalic Acid. It sounds as though you are
going to have to strip the finish off of the stain before going at it again.
Make sure the Oxalic Acid solution is saturated and let it sit until dry.
You will have to wipe up the resulting dried crystals with a damp cloth. Do
NOT brush it up. It will have you sneezing your brains out if you sweep it.
Also, do not let the dog anywhere near the spot when it is being treated.
Oxalic Acid is quite toxic.
If you can manage it, try to have sunlight hit the spot while it is
being treated with Oxalic Acid. The sunlight will help bleach the stain.
I would try hypochlorite bleach if the second treatment with Oxalic Acid
did not work. I have used swimming pool hypochlorite instead of "Clorox"
since you can make it up to be a stronger solution.
I would move onto the two-part wood bleach, caustic and Hydrogen
Peroxide, as a last resort.
Once you get the stain out, I bet you will have to recolor the area and
then spot finish it. This will not be fun.
Good Luck.
"whit3rd" <[email protected]> wrote in message
news:[email protected]...
On Feb 4, 11:11 am, John Martin <[email protected]> wrote:
> I scraped down through the finish before using the oxalic acid the
> first time. Have used it probably three times, and each time it was a
> hot solution as saturated as it would get.
That may be a problem; oxalic acid is unstable, it wants to
stay cold (and of course, you have to handle it with
glass or plastic, it gets poisoned in a steel or stainless
container).
It makes iron stains go away by dissolving the iron, but you
want to rinse away the solution or the iron comes back
again when the oxalate destabilizes.
Rather than scraping, I'd use a chemical stripper.
It's much easier, and finish penetration might defeat scraping.
Hello,
Oxalic acid is not really unstable. It has a melting point just above
the boiling point of Water so hot Water should not be a problem. A solution
kept at ambient temperature works just fine after several years.
I assume you mean that a hot solution "wants" to cool to ambient
temperature. A hot solution will hold more of the acid than a cold
solution. As the hot solution cools, the acid will crystallize. I have
never found that to be a problem other than it leads to more dry crystals to
wipe up after the iron has been chelated and the stain removed.