20% Fabric Softener, 80% Isopropyl Alcohol

[paul678]

That's what I've read is a good solution to soften old, hard hammers.  Needling
is still required afterwards.

Any tips on how to apply the solution?  With a brush?  How much?

I think someone mentioned not putting too much on the striking point....

[pristinepiano]

I have done this years ago to an old upright as an experiment.  The hammers had already been carded/sanded and the hammers were near the end of their life, very hard and tinny sound was coming from them.  I flipped the action on its end so it stood vertically and applied  drops (with eye dropper) on the upper half of the hammer felt about a 3/8" back from the crown, and then the lower half.  I then flipped the action over and did the same thing from the other side.  Eye dropper is essential to keep the amounts the same.  4 drops total for the treble hammers (2 per side), 8 drops for hammers down to the tenor, and 12 drops for the largest bass hammers.

It did not work too well and I ended up doing some deep side needling to help get what I was after.  In hindsight, I would not do it again in this type of situation, it was a waste of time. It also made some unsightly "puddle marks" on the sides of the felt since a 100+ years of dirt and dust is hard to remove.  Blow off the hammers real good with pressurized air first if you wan't to minimize this on older hammers.     

[faulty_damper]

Even isopropyl alcohol doesn't work by itself so I doubt adding fabric softener will work.