Restoration of the

Duo Art Expression Box

Duo Art Expression Box

This is a documentation of an expression box rebuild from a Steinway grand in California.  The local tech sent it to me (without the piano) for restoration.  Most of the accordian pics are from a Steinway upright in Texas.  The only difference is accordians from an upright will have two adjustment blocks instead of three per board like in the grand version.  

1. Accordian pneumatics

The Accompaniment accordians were recovered some years ago while the Theme accordians were still original leather hanging on in shards.

Numbering the pieces is important to get every piece of wood put back into its original position.  It seems it would not matter but it does.  Get them out of order and they do not line up.

Notice that upon removal of the recent cloth the old leather remains on the wood under the glue.  This caused the new glue to have a chemical reaction with the leather and original hot glue making for cloth that was loose and allowing two or more cells to bleed through and activate together.  The cloth came off really easily.

All boards have been sanded to the wood and shellacked, and the spacer blocks have been cleaned and painted and have new felt on them of the same thickness as original felt.

Covering the accordians requires specially made spacers.  The whole stack of boards is clamped up and lined up with a straightedge on every side.  They are then covered with pouch leather just like the factory used.  The original leather was tan and it was vegetable tanned.  We use chrome tanned.  Testing has shown that chrome tanning makes the pouch leather last 30-50 years in our modern polluted atmosphere which deteriorates the vegetable tanned leather within six years.

After spacers are removed the fourth side is glued.

Then the newly recovered pneumatics are sealed with egg white as the factory did.  Egg white has been used as a binding agent and sealer for leather for centuries.

2. Accordian pneumatic valve box  next page

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