A friend of mine had an Ampico "B" grand piano professionally restored
three years ago. It was a very costly and complete restoration that
when finished played lively and loud with wonderful expression. This
was one of the finest piano restorations we had ever heard. Over the
next two years it continued to play very well.
But in the last year the trouble began: some notes became sluggish and
began to play soft. Eventually some hammers would hardly move at all.
The problem seemed to be getting worse each month to the point that it
was no longer possible to enjoy this fine piano.
The decision was made to "pull the pneumatic stack" to check-out the
problem. At first glance the bellows cloth seemed to be in fine
condition. After pulling the stack apart small grayish white particles
were found in the valve and pouch area. Each valve and pneumatic was
checked for leaks; many were found.
The particles were found to be a "Bondo" type polyester body filler
that was used to repair the splinters and voids left when some of the
pneumatic boards and valves were sheared from the stack. We have all
seen this sort of repair and it is a widely accepted rebuilding
practice among restorers for many years. You can see photos of this
filler repair on this site as well as the web. In this case the
polyester filler had shrunk, and in some cases it had released its bond
on the wood.
I have known about body filler shrinkage on antique auto bodies for
many years. The signs of an older "Bondo" repair are the spider web
like cracks that begin to appear in the cars paint. Sooner or later
large patches become loose. This is why I prefer the more costly old
fashioned lead filler that lasts forever. But it's hard to find anyone
willing to do lead-work on cars anymore...
But what about this use of polyester body filler on defects on pneumatic
bellows boards or valves? In my friend's piano, the polyester filler
has failed in three years. The entire action must now be re-built or,
better yet, re-constructed with new wood. Has anyone else seen this
"Bondo" shrinkage and bond failure?
Has anyone rebuilt an action that had some "Bondo" repair work done in
the past? If so, what was the condition this old filler? Is there any
filler that is better that polyester body filer and will last longer?
I would bet that this is not an isolated case.
Huntingdon Valley, Pennsylvania