Sandpaper that clogs is usually the wrong grit
I sanded a patch of filler over a door strike on a damp February afternoon. The sheet went smooth in six strokes. White paste packed every grain. I turned the paper over. The other side lasted four. I thought I needed more sheets. I needed a coarser grit, and filler that had actually gone off. I was polishing a damp plug with a face meant for a last pass.
Sandpaper is grit stuck to a sheet. The number is how fine that grit is. A low number cuts. A high number finishes. If you put a finishing sheet on a lump of filler, the lumps fill the gaps between the grains and the sheet becomes a slick pad. It skates. It shines the filler and does not flatten it. People blame the paper. The paper was doing a polish on a job that still needed a cut.
I keep it simple. Something around 80 if I am knocking a proud lump back. Around 120 once the lump is close. Around 180 or 240 before paint, on a face I already flattened. I will not pretend those are laws. I will say I change as soon as the sheet stops cutting and starts sliding. A clogged sheet is information. The grit is too fine, or the filler is still wet, or both.
Filler that shrinks is usually the deep hole is why I am often sanding a plug I should have layered. If the face is still cool and dark, I do not sand. I wait. February rooms dry slowly. A radiator on will skin the face and leave the core soft. The sheet clogs on that skin and then smears the core. Summer with the window open goes the other way. The face is ready sooner. I still tap it. If a nail leaves a mark, it is not ready.
When the sheet clogs I do not keep pressing. I fold a fresh bit, or I take a new piece. I knock the dust off and look. If the grains are full of white, that piece is finished. Washing it is a fiddle I do not bother with on cheap sheets. I change. I also dust the wall before I paint. Dust under emulsion is grit you rolled in. A roller that sheds is usually the cheap sleeve is the coat after this. Fluff and sanding dust together are a finish I can see from the door.
Sugar soap that streaks is usually the rinse is the wash I do after a heavy sand on a greasy wall, not instead of sanding. I sand, dust, then wash if the room needs it, then rinse. Soap on a clogged, smeared filler patch is a streak with grit in it.
Skip one grit for the whole job because it is what was in the drawer. Skip 240 on a crater. Skip 80 on a wall you will roll tomorrow and then wondering why the scratches flash. Skip sanding in a circle until you have a hollow. Straight passes, then a wipe, then a look in raking light. Skip a worn sheet you keep because you paid for the pack. A dead sheet burnishes. That shine will flash under paint.
UK year is mostly about drying. I sand less in a wet January and more in a dry spell. I would rather wait a night than clog six sheets and still have a dish. The paper is not the scarce thing. The flat face is.
If scratches are already under a dry coat, I do not keep rolling. I sand the flash with a finishing grit, dust, and put a thin coat on. Another cheap sleeve will only print the scratches in a new colour.
I do not need a different filler because the last sheet clogged. I need the right grit for the stage I am actually at, and a plug that has gone off.
If I later add a buy link here, it will be a paid promo.