I'm attempting to refinish a parquet floor so that I can get my family moved into our new house before the new school year begins. I have a lot of DIY experience in just about every other home improvement category imaginable, but this is my first attempt at refinishing a floor. I started with a drum sander and progressed through grits 36, 60 and 80, alternating directions with each grit. I then mixed some of the 80 grit dust with Glitsa Wood Flour Cement and coated the entire floor, in order to fill the many large gaps between tiles. I then used the drum sander again with 80 and then 100 grit paper. I finished with a square buff sander using 80 and then 120 grit, then I cleaned the floor and "water popped" it to help the stain take.

The floor looked great!.. until I stained it.

I have 3 main problems:

(I tried to post images after each description, but received an error that, "It was not possible to determine the dimensions of the image." Here is a link to the gallery: https://postimg.cc/gallery/2rz09afbi/ )

* Discoloration that often spans multiple tiles. The lighter area usually feels smoother, so somehow it seems that these areas were sanded finer and did not take the stain as well.

* Wood filler that filled the wood grain, rather than gaps.

* Drum sander lines from when I was sanding across the grain.

Here is a photo of one of the better sections of floor. I really think this can look great, if it can be saved.

(Photo in previously linked gallery)

My guess is that my error was either using the square buff sander as opposed to some other random orbit, or not making enough passes with it. I'm just not sure what to do, at this point. I was going to take my little osculating tool and go tile by tile, sanding down the discolored areas and then reapplying stain. That just isn't working well, though. The stain just does not apply evenly unless I sand down the entire tile. Even then it just doesn't quite look right.

My main issue is the discoloration from both the apparent uneven sanding and the wood filler. They really look like crap, from a distance and up close. The drum sander lines I could probably live with. They might drive me crazy but I don't think most people would notice them. They're also mostly just in one area of the house. The discoloration issues are everywhere.

Would a random orbit sander like this help my situation?

https://www.homedepot.com/tool-truck-re ... index.html

If so, would I need to get 100% of the stain off? Could I use it only in spots, or would I need to do the whole floor? I'm assuming the latter... How many passes? My big fear is that I spend a day doing something like that, then another day staining, then find out nothing has changed. Like I said, I could not see these issues until the stain was applied. I looked pretty hard, too.

These tiles are engineered and I'm pretty confident there isn't enough veneer left to use the drum sander again.

Any help would be greatly appreciated.

The best time to fix a m essex up stain application is when the stain is fresh and hasn't dried. Sandpaper will gum up no matter what machine you use, unless using a coarse grit. A sharp paint scraper will remove the surface and leave shavings instead of gummed up sandpaper. Use a mill bastard file to keep the scraper razor sharp so you don't need to use a lot of pressure. After scraping, then the surface needs to be "opened" with medium sandpaper with the grain. Popping the grain complicates things. If you are worried about sanding through the veneer, I would scrape each tile. Using #2 steel wool to even out the stain by scrubbing off dark areas to match the light areas can make a big difference. You may need to use Polyshades colored finish to get close to even. Water-based finishes discourage wool because of rust potential.
Even though looking from head height down is the standard for floor acceptance you need to be on your hands and knees inspecting the floor as you stain to get a nice job as you apply the stain. If the tiles aren't fastened down well the filler can fall out as the parquet moves cracking the filler. It will take a lot of work to salvage the floor. Call your homeowners insurance to see if this disaster is covered.

Are you saying that I should scrape the floor only if the stain hasn't already dried, or even if it has. It is definitely dry, unfortunately.

Also, you're saying that I can scrape only the problem spots within each tile and then even it out with steel wool? As opposed to scraping the entire floor? The stain that I used was a Minwax oil based stain. It was not a poly shade.

The advantage that parquet presents is you may isolate each unit, if they are squares. Scraping vs. sanding with any machine would be the bast method since you're worried about sanding through the veneer. As the stain is being applied and still wet is the look you will have when the stain has dried and has a coat of finish applied. This was the time to correct the workmanship. A dried and hardened area will show the "look" by wiping paint thinner over the area. Steel wool can "wear off" some excess color to lighten an area. Scraping and hand sanding and then staining again will be the best that you can do, now.
After you have worked on the floor to even it out you may need one or two coats of a colored finish. A clear finish over everything will prevent the color coats from wearing off soon.