The Rot Doctor


Subject: Can CPES restore aged and or delaminating piano 5 ply rock maple pinblocks?
Date: Sat, 15 Mar 2003

I rebuild pianos and am curious as to whether your product could be used to strengthen or restore old rock maple pinblocks. The pinblocks are often made out of 1 1/2" thick 5 ply quarter sawn rock maple laminates. The pinblock is then drilled with a .271 diameter drill bit about 220 times to hold the corresponding number of .280 tuning pins. Tuning pin holes are usually between 1/4" to 1/2" apart often in rows of 3 with a little more space between rows. Tuning pin torque is ideally at around 120"/lbs at first but gradually drops to around 30"/lbs at which point it can no longer hold the piano wire at pitch at around 150 lbs of tension. The pinblock is mated to a flange in the cast iron plate and screwed into place. With the piano tuned at pitch the pinblock is resisting about 33,000 lbs of tension. It is extremely important that the "feel" and torque of each pin is consistent with no "jumpy", tight or loose pins. Delaminations often occur after the initial pin torque begins to drop too low and a technician pounds the pin in a little bit to try to give it a little more "bite". The old brittle hot hide glue joint shatters and gaps may form. The pin block is now said to be ruined.

If the piano is a high quality grand it is often worth while to restring and replace the pinblock. However, it is an expensive procedure and most uprights and lower quality grands are not usually worth the cost. Could your product be used on such instruments to restore the pinblock to usable condition. If it is possible, could it be applied carefully at the base of each pin and allowed to wick into the pinblock, or would it be best used only after removing all of the tuning pins and the cast iron plate and swabbing the holes with CPES?

Would hazing or wax buildup be a problem?

Thanks in advance for your answer,


A complicated question, and one with no exact answer. CPES (Clear Penetrating Epoxy Sealer) will help to strengthen wood, and will, to some extent, help prevent delamination. Depending on the particular situation, several coats may be required.

I do understand what you are saying about the mechanics of the pin blocks, and there is no doubt that the CPES would improve them. Whether that would be enough to meet your expectations I cannot say. Gibson Guitar does use CPES as some part of their operations, but I'm not sure whether it is in manufacturing or repair.

Wax build would retard the ability of a flat wood surface to absorb CPES, although it might well penetrate into seams. The CPES would most likely dissolve the wax.

The best advice I can offer you is to buy one of our 2-pint units ($33.00 plus UPS Ground shipping) and do some testing. Be aware that when first applied CPES is volatile and produces strong solvent fumes. These can be dissipated with a fan or open windows/doors.

Thanks for the complete description of what you want to do, and feel free to come back if you have additional questions.


Note: Current pricing on all our products can be found on the Product Information page.