Remove residue from wooden floorboard?

Hello everyone,

Yesterday I removed a linoleum or Stragula floor. On the wooden floorboards, there is now a blue/gray felt-like residue left behind.

What could this be and how can it be best removed?

P.S. The floorboards are not going to be refinished - a new flooring will be installed on top. Due to different heights, I decided to remove the previous covering and then level it out.
Attached graphics

We rented a machine from O?i for this. It has a kind of blade at the front and lifts the residues quite well with it. But I can't remember exactly what the thing is called.

We borrowed a machine from O?i for this. It has a kind of blade at the front and lifts the remnants quite well. But I can't remember exactly what the part is called right now.

The device is called a carpet stripper. Unfortunately, you can't remove all the soft adhesive residues with it either.

Hello questioner. Stragula is a really old type of flooring, which came onto the market due to raw material shortages at the end of World War II. So if the old covering was indeed a "Stragula," no renovation of the covering would have been done in the room in the last 65 years. However, there are also other (more recent) coverings that had a jute backing. As a result, during removal, only part of the jute fibers are taken up with the covering, while the rest is still firmly bonded to the adhesive on the screed surface. There are 2 ways to remove these: a) For small room areas, you can "take on" the work and work piece by piece with a so-called scraper. A face mask and vacuum cleaner should be used (the small fibers in the air are unavoidable). b) For larger areas, it makes sense to work with a disc machine and wire brush attachment. This is the fastest method. A stripper, on the other hand, is not the optimal solution, because only the coverings are peeled off, but the adhesive (together with the adhering jute fibers) remains on the floor. ---------------- Regards: KlaRa53 (new here in the forum)