I’m not an expert but I still thought I should tell you how I sorted some damages done to the wooden floors of our rental and which technique really worked.
Because you see I have an issue: I love plants, I dislike plastic pots, I love hardwood floors… What could go wrong?! Well, it’s kind of obvious but let’s dive in!

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Let’s just start by the obvious that I have more than one issue 😉 but this one had to be handled before we moved out.
Indeed, some of my plant pots leaked and before I even knew it, there were dark spots on the wooden floors of our rental apartment.
Not that I can blame it all on my plants, because, actually, there was a huge discoloration in front of the doors leading to the terraces too. And I know my plants didn’t go in and out! I know we did. I know sometimes our feet were wet when we came back in. We used to leave our shoes on the carpet in that spot and the carpet got damp and the dampness ended up messing up the floor. Now, what didn’t help is that the varnish had been damaged by the sun and left that spot ‘extra sensitive’.

It was not noticeable at first or I just didn’t pay attention. It really felt that it happened suddenly, just a few months back, bam, the discoloration was there.
I thought at first that it was just that the floor around the carpet got lighter with the sun. But it wasn’t. It got worst and worst quickly, once the process had started and it had the same look as a water damage, with strings of dark / moldy wood.
I had to do something! So I googled.
Things I tried which absolutely failed and sometimes made things worst
To be fair, the product that worked seems to be well-known. At least to professionals. Yet, google keeps giving other recommendations first. Here is a list of things google made me try:
Baking soda with toothpaste! Yes. White vinegar, of course! Different types of soaps. Some swear sanding is the only way to go. Others swear by bleach. Some simply use salt.
I tried it all! Except for bleach because I don’t have any and I am kind of scared of bleach.
Nothing worked and actually sanding the floor made things so much worst.
So I went to a store and asked for something magical. I left with acetone and a new varnish.
The acetone did absolutely nothing! Actually, maybe because the floor had been sanded, it made things worst than ever. The floor became kind of orange. I sanded some more, it was kind of ok. But when I applied the varnish, the orange color came back. The varnish was just absorbed by the wood and the discoloration was brought back. I think! I don’t know. Anyway, the result was disastrous!

I was on the verge of giving up but went back to google once more and then Amazon…
And there… I found Oxalic acid and I can’t believe the results!
Oxalic acid is apparently often called wood bleach so that should have been a great indicator of the potential results.
The one I bought had instruction on it in terms of quantity and duration of use. I did it several times in certain spots and it worked wonders.
There are a lot of recommendations out there on how to use. It probably depends of the product you buy. Some use hot water to dissolve the crystals, some brush the product in, some leave it for 10mn and some for 2 hours… some just use water to neutralize it while others use baking soda. Some sand the wood before and after…
It really is difficult to know what technique is best but I’m guessing it all depends of the wood and the stains.
One usual recommendation is to test it somewhere where it won’t show, but since we were moving, there wouldn’t be a single place on the floors that wouldn’t be visible!
So I tried it right away, in the area I had already messed up anyway! A very visible area I should add. But just on a tiny tiny portion, at first. It showed improved at the first application so I extended the area and every application showed improvements. I did it at least 5 times and was then fairly happy with the result, so I moved to the next area.
I didn’t take before pictures of the first area treated because I didn’t think about it. I didn’t take many pictures during the process either!
But here is a picture after a couple applications.

As you can maybe see below, the results were not so bad. Actually, if you din’t see the before, in real life, you wouldn’t be able to tell something was done. It’s not obvious. With pictures, it’s a bit different.


The only obvious part after that was the discoloration due to the sun exposure!
So I was quite happy! It got sorted a little too last minute to my liking but it was mostly sorted anyway.
To be fair, I should mention that I did use the varnish bought in store on the bathroom cupboard. And it did wonders there. It was sold to me as a clear varnish, but I don’t think it was entirely clear, hence maybe the orange color on the very light wood in our former living room.

In addition I should also mention that the Oxalic acid didn’t do much good on the kitchen floors. We had a window there, with the same sort of issue: varnish damaged by the sun in front of the door and occasional wet shoes. However, I should also say that I didn’t try to sort out the issue there a whole lot. I had given up slightly and was afraid to make another mess.
The moral of the story?
Don’t always trust google! Don’t always trust the guy at the store either! Put something underneath your plants. Find a waterproof rug / mat, or something waterproof to put under your rug if you have a terrace or any sort of outdoor area! Don’t let any damage get out of control.
PS: Oxalic acid apparently remove rust as well. Thought you should know. Guess what I’m going to do with the rest of the bottle? Clean the gas tank of the Peugeot, of course! The citric acid helped but didn’t do a full job. Maybe this will do wonders, we shall see.