Compression Ridges

[JCSwafford@AOL.COM]

Hello List,

I recently inspected a new Mason & Hamlin Model A for a customer. It was a 
fantastic piano, but I found several ridges in the soundboard. I could feel 
them as I ran my hand across the underside of the soundboard. They protruded 
upwards. 

I mentioned to the customer that in my experience these ridges are fairly 
common in pianos built today with solid spruce boards and was the subject of 
controversy between Steinway and a dealer not long ago. I told her I wasn't 
very knowledgeable about them and they may not even be compression ridges at 
all, but irregularities in the joining of the planks of spruce when the 
soundboard is constructed. I told her she was not likely to have any problems 
from them in the future and I would consult the list to order to give her a 
well rounded opinion about them. 

I explained that compression ridges occur when the board is dried to much in 
the kiln before installation and the installation is to tight to the rim of 
the piano. The ridges occur when EMC is returned to the board not giving it 
enough room to expand without compressing. 

I haven't studied soundboards, their preparation or installation techniques.

May be I can get some feedback from some of you knowledgeable rebuilders or 
intellectuals out there.

Thanks for your help in advance.

Joel Swafford, RPT