(edited for a few typos and omissions)
Getting into this late. Lots of different opinions. I'd be curious to know what you did exactly that was going too far. Makes a difference on how you approach recapturing some of the lost power (I presume that's what you're concerned about).
Generally I am not a fan of reshaping hammers to something other than their original shape. Usually this means making them pointier when they aren't naturally that way. On some hammers it doesn't really matter, for example, hammers that have a fair amount of lacquer in them. The lacquer binds the felt and so cutting through layers of what might have been tensioned felt doesn't really have any impact on the overall hammer structure. Sometimes reshaping a hammer to be more pointy shape when it isn't that way naturally can take something off a hammer. For example, with Renner Blues that are too hard, you can take something off of them by filing them to a point and the process of cutting through layers at the crown will cause it to "relax". The crown will lose some of the tension that keeps the crown firm and soften up. But you're really killing those layers so I wouldn't recommend this unless you're desperate. It might have the opposite effect than you want. There are some hammers that have been pressed to the point where there isn't any tension or reactivity left in the thing anyway so it doesn't matter what kind of filing you do, they probably won't sound good anyway. But in this case I believe it is better to maintain the original shape.
If you've killed the hammer by too much deep needling close to the crown then it's difficult to bring that back. You can try, as suggested, pounding on the crown to try and set the felt using a small hammer, even using the rounded pein side of the hammer can help in this case. Some hammers will respond to needling below the staple (battery voicing it has been called) but not all hammers will and I don't believe the Abel Natural will respond to that. You can file some of the dead layers off the top but depending on how you needled the crown you may or may not achieve the desired result and may simply change the blow distance, mess up your mating and shorten the life of the hammer for naught.
If you are, as you describe, only slightly below the level you want then I wouldn't do a lot. Sometimes the cure is worse than the disease. Using keytop solution for this is, in my opinion, a definite no. Keytop offers a quick way to bring back some "ping" or brightness on the strikepoint of the hammer but I think it is best reserved for concert situations where you must have results now and not later. The material is otherwise relatively unforgiving, tends to form hard spots and and can make for unwanted noise that will be heard in a more intimate setting. Recall that the very crown of the hammer is typically not crystalline at all but rather just the opposite--a softish outer coating that gets progressively harder as you go deeper. Not a hard outer surface and one that gets softer as you go deeper. That's bassackwards.
Nor would I resort to adding lacquer at all and certainly not any hard setting lacquers like sanding sealers or table top lacquers. Not a good match for that hammer. If you have to use lacquer use a soft setting lacquer like Pianotek's Pianolac and use a 10 - 15% solution (10-15% lacquer 85 - 90% thinner. Apply from the shoulders and let it wick all the way under and to the crown. Use lacquer thinner as it flashes off slower and allows for a more complete creep. Keytop solution should not be used for general hammer saturation under any circumstances, in my opinion.
However, if it were me I would try and set the felt with some blows with a small hammer as described and then polish the top of the hammer with progressively finer paper up to 1000 grit. Make sure that the hammer string mating is precise and let the hammer play in for awhile. The setting of the felt and polishing should give the tone a shine and clarity even if it lacks some power. Those hammers do tend to play in fairly quickly, as far as hammers go, and will come up over time. Once they get to where you want them they will likely have some greater stability than either using hardeners or filing this natural hammer into an unnatural shape.
Good Luck and Happy Holidays.
------------------------------
David Love RPT
www.davidlovepianos.comdavidlovepianos@comcast.net415 407 8320
------------------------------
Original Message:
Sent: 12-20-2017 10:19
From: Mike Ello
Subject: Voicing Able Natural Hammers
So this Kawai KG-1D had rock hard hammers. I replaced the hammers with Abel Naturals. So I went too far and the hammers need to be hardened just a little bit. I have done a whole set with lacquer but would like to use acetone and keytop solution. I have used acetone and keytop solution for spot voicing but never for a whole set. Could anybody give me some guidance how to approach this type of voicing?
Thanks.
------------------------------
Mike Ello
Richmond TX
281-633-0622
mike@ellopianoservice.com
------------------------------