How to fix floorboards blotchy under old cabinets?

[dr_harika]

Hi. I have ripped up an old kitchen island return and under it is raw pine floorboards which I want to blend in as best as possible.

I'm installing a new kitchen but it only goes along the wall and not a return like the old one leaving some unfinished floor exposed

The property is a rental so keen to get something to fix the issue as quickly as possible. It's also a mixed bag of floorboards. Most is hardwood and this small kitchen area is pine.

I've sanded the raw pine section back to flat as it was 2-3mm higher than the rest of the floorboards. I used a nail punch to drive the nails in further too. 

Now the problem is there seems to be blotches in the wood.  I misted water on the floor to show the colour it will come out when I use a water based polyurethane but I'm not impressed so far. 

What should I do to fix this? 

Before sanding 

 after sanding and trying to match the existing levels:

And this is the wood after it's been wet with water. See the blotching?

 

[JacobZ]

Hi @dr_harika,

It looks like something has been spilled on them, and then it has soaked in and stained the timber.

Water marks and stains like this can often be removed using an oxalic acid-based cleaner, such as this Diggers Rust And Stain Cleaner, which is a light bleaching agent that is often used in timber restorations.

Start by mixing it with clean water, following the ratio recommended on the packaging, then applying it to the floorboards and scrubbing.

Mix 100g of Diggers Rust & Stain Cleaner in 1 litre of water and mop the solution over the entire area, and let it soak for a few minutes. You can then use a stiff brush to scrub the surface. You should then use your mop to clean up the solution and then flush the boards with clean water to remove any residual chemicals.

This should help to remove the water stains and give the timber a more even finish before applying your polyurethane sealer.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob