I've used Simple Green sprayed on a cloth with limited success. It takes persistence and patience, and it won't make them look like new, but it does help. Maybe a weak bleach/water solution also. Don't saturate the beater felt, just wet it enough to clean the surface, then let it dry.

Just speculating here but maybe the dish washer would work.

I've had good luck with an aerosol carpet stain cleaner called Spot Shot.

I've also tried aerosol carpet stain removal with good results!

-Mark

Oh, man, that's great news! After decades of dogs and cats, we've accumulated plenty of carpet cleaner.

Did you use a brush or anything once it was sprayed on? That's what one of our cleaners says. Or 'agitate with fingertips.' (There's a joke there somewhere)

I've thoughts of resigning to the spray on fabric dyes. But I think the felt would absorb it all with no results.

Many beaters have interchangeable felts, but the Ludwig is held by just beating the end of the metal. It could be removed, but replaced? I've never tried it.

Yesterday I tossed some beaters that I was able to detach from the shaft into a load of laundry. They came out pretty clean! Nice and simple.

Has anyone successfully taken a Ludwig beater apart? They're held in place by smacking the top of the shaft with a hammer-well, it's industrial equivalent- until the top is misshapen enough to hold the top in place. I know I could drill it out, but I don't know if there would be enough left to smack it back in place.

Then again, some of those beaters are so ugly, what's to lose?

Since most beaters are made from felt, doing a search about how to clean felt piano strikers or felt hats might yield some insight.

Of all the wacky things, I tossed them into the washing matching. That was more successful than anything else I've tried.

Next time add bleach. Do them like whites.