Destaining Tiles, Mechanically

Also see, for algae : http://sextechandmergers.blogspot.com/2024/02/dried-algae-organics-on-tiles.html

Update 2024-01-30 :

Perhaps finally optimised. "how to clear primary marks".

1. With an automated sander.

2. With P60 grit paper, and a wet substrate.

3. Select a target spot.

4. Place grit upon substrate before spinning.

5. Apply slight pressure against substrate, and apply movement along the plane of the substrate to diffuse pressure, while moderately spinning up sander.

6. Increase speed and pressure, with corresponding diffusion and rewetting across the plane, until spot is clear. This will probably have generated secondary marks from the sanding.

7. Now, address secondary marks. With the same grit of sandpaper, repeat steps 3-6. while feathering power very gently, until secondary marks are minimised.

8. As preferred, repeat 3-7. with finer grades of paper.

\\\

Update 2024-01-26 :

# of ops on a 15cm x 15cm tile : 

- divide each tile into 6 columns

- each column is scrubbed 2 times per count

- counts per pass are 1,2,3,4; 2,2,3,4; ... 8,2,3,4

- passes are repeated for 3 grades of sandpaper

6 columns x 2 scrubs x 32 counts x 3 grades = 1,152 operations per 15cm^2 tile

# There are 100-200 tiles per bathroom.

This is why I was trying to find a way around the manual route. But I failed. So I am doing it manually.

\\\

Initial post :

Study of tile destaining by mechanical effort : 

1. Be fully aware of how tiles are internally structured, and of what layers you remove - you may want to replace those with coatings later.

2. Sandpaper grit that is too coarse (lower numbers) will scratch, grit that is too fine (higher numbers) will be consumed too quickly.

[ ISO 6344 : roughly, P36 means 0-tolerance for 1mm or larger particles, P300 means 0-tolerance for 0.1mm or larger particles ]

3. Never sand without lubricant (water is fine), as the distribution of destructive forces has a much higher variance when unlubricated (leading to an increase in output variance, from the function).

4. Sanding with a low speed (e.g. by hand) is ideal. 

4.1. There are many types of automated sanders ... the simplest (pic) is a non-random orbital sander. It is harder to find ones that go down to 100RPM, but 600RPM seems common. You are not supposed to apply much weight when sanding - the calibration technique is to spin at a consistent speed, while using alternate grits as needed. Random orbital sanders further reduce output variance (see 2.), and should be used whenever possible, instead of non-orbital sanders. ( Sanders may be deisgned to use sandpaper discs, or a quarter of a standard sheet.) There are also belt sanders, and drum sanders which are more aggressive.

4.2. I find that a first pass using P60 with automation is a quick way to get started on very thick stains. Remember your water (see 3.). But generally, with or without this rough pass, I find it easiest to work with P180 by hand.

4.3. To reduce strain on finger joints, a sanding block may be used. I like to fold a small towel into triangles, to give me a knuckle-shaped "block" which I can hold comfortably.

More tests required, but this is the long and short of it. #jerngvswork