it worked.

Torching also worked on some XT pads that after sitting for a winter had no bite… Cleaning and sanding alone did not help.

I never clean my disc brakes, both pads and rotors. Never noticed any degradation in performance since brand new. I only use metal-sintered pads - the ones that make loud noise so peds can hear their impending doom.

Maybe because I regularly go up mountains with long and steep gradients, I probably use the brakes hard and long enough to make intense heat and vaporize any unwanted stuff on the brake pads and the rotors. :)

IPA on the rims about weekly. In the rare case that pads are glazed, sandpaper.

I think the reason you find sanding helps or is needed is that you’ve got contaminated pads. Sanding is often just a temporary solution, as the contamination makes its way back to the surface.

Brake dust should have no negative effects on braking, and unless you have comtaminated the pads and feel a decrease in braking, there is no reason the clean/sand them, which is why no manufacturer recomends doing it as a part of regular maintenance.

I think it's the organic pads that can get contaminated easily and can get glazed. The sintered pads can handle some typical oil contamination that comes from wet roads and you can vaporize the oil contamination on long and steep descents. I only read that sintered pads are not good to use on hydraulic brakes due to heat conduction. But I have fully mechanical disc brakes and no problems whatsoever except for the noise. However, the noise is only temporary with new pads. They'll go away with use.

I'll clean the rotors occasionally with automotive wheel cleaner that is suitable for painted wheels. I've never cleaned the pads and haven't felt the need to..

So assuming that the rotors are clean, this should help ensure that the majority of potential contamination doesn't make it's way to the pads?

Since sanding works really well , temporarily, how can I prevent contamination, period?

Don't ride your bike.

Aside from the obvious stuff like keeping oily stuff off the pads and rotors..... Just ride the bike and hope for the best. Sometimes it just happens. By road bike pads have never gotten contaminated, but my MTB pads have, and I really don't know how. For some reason when my XT pads on my MTB sit over the winter, something happens to them and the act like they are contaminated. This year I picked up on the blowtorch trick and it worked.

I have no opinion on bikes but for cars and trucks this is backward. For years I was responsible for a maintenance department with a fleet of 251 mobile vehicles from cars to 350 ton haul trucks traveling up and down open pit mine haul roads and spent a lot of time studying this issue and the literature is clear.

The literature might be clear, but your answer here is not. Even for cars and trucks I'm not all to certain which way you lean.

Firm braking (at least for cars and trucks...) Assuming you're not locking up the brakes or braking too hard, helps recondition the pads/rotors and promote even wear, assuming that everything is mounted properly. Assuming we all have the same idea regarding "firm" , what he was saying makes sense. It's actually important to occasionally do some firm "bedding" type stops here and there when the brakes are often subjected to uneven use patterns with Insufficient heat build up, using them lightly, or too hard, whenever they ARE in use.

Acta retracta?

Rim brakes - I regularly hose my bikes off with a light spray but blast the brake shoe from both directions to both clean out the ugly black dust and remove any grit.

Right now I have a little tubular glue on my rear rim and a shudder when braking. Persistent stuff! I've done two cleansings so far with Simple Green, paint remover and dish soap. Better each time but still there.

This is my understanding also. On a long descent steep I brake several times and coast vs just one long brake.