Restoration of a Knabe Concert Grand
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1) The keys are being glass bead blasted to remove dirt and tarnish. Also at
this point the old key bushings are removed and the old back checks are removed for
replacement with new Steinway style back checks.
2) Rebushing the keys. After rebushing, the keys will be sent out for new
keytops.
3) Removing the old action parts.
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4) A pile of old action parts to be discarded. The action will be replaced
with new Renner parts.
5) A few of the key buttons were slightly weak near their sides.
Therefore, I installed mahogany veneer slips onto the sides of the buttons in
question. First, I made sure the sides were sanded very flat and straight, then I
glued the slips on with hot hide glue and clamped them into place using glass for clamping
cauls.
6) After the glue had dried, I sanded the slips to ensure they were flush and smooth
on all sides and to ensure that there were no places where the key sticks might come into
contact with each other at the repair slips. Fortunately, on this piano, there was a
good amount of space between the key sticks which made this type of repair possible.
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7) The let off rail before the let off buttons were replaced. All felt is
glued down with hot hide glue. Also, all joints which may some day need to be undone
are always put together with hide glue.
8) A picture of the action rails and brackets before any of the old felt or sand
paper were removed. While the old felt was still in place, I dismantled the entire
assembly and glass bead blasted all the parts with the finest glass bead available.
This cleaned all the wood and metal parts very well without causing any damage to the
parts. Afterward, all the parts were treated with a coat of lacquer. After the
lacquer was dry, all the felt and sand paper were removed for replacement.
9) I always put my let off buttons into clamps for a while before installing them.
By so doing, I'm able to stabilize the felts so that the let off will stay where I
put it when I regulate the action.
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10) The original hammer return felts were made with a very nice
system. A thin layer of felt was sewn to a thick upper layer. The thin layer
is the only thing that gets glued to the return rail. In so doing, you silence the
hammer return more than if you simply glued action cloth to the return rail directly.
11) The completely restored action rails and bracket assembly.
12) The capstan's sides had been cleaned by glass bead blasting. Now the
friction surfaces are given a super high polish.
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13) Some of the wood parts of the key frame had lost their glue joint in years past
and fallen off. They are now missing so new ones had to be fabricated. You can
see one of the new pieces in this photo.
14) Before removing the key pins or sending the keys out for new key tops, the
action is measured to determine what sizes of underfelt and key punchings will be needed.
This way the new felts can be ready for installation by the time the keys come back
from the key top replacement experts.
15) Here you see that all the new punchings have been placed into clamps and put
under enormous pressure. By so doing, they can be stabilized against compacting once
they are put into the piano. This keeps the action regulation more stable.
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16) Here you can see that someone previously replaced the back rail felt with felt
of the wrong size. They also failed to scrape off the old glue from the original
felt before installing this "new" felt. The result was that these felt
strips had all come loose. Even though the felt itself was still in good condition I
removed it and replaced it with new felt of the proper size and character.
17) In this picture, the key frame has now had its old key pins removed and the
frame has been glass bead blasted. Now the new back rail felt is being glued into
place. A central strip of underfelt is installed first. Then over this a layer
of back rail felt is stretched and clamped into place. No glue is applied between
the strip of underfelt and the back rail cloth. This will provide a silent and
stable result that will last for decades without changing.
18) After the new back rail cloth has been glued into place, boards are placed over
its entire length and clamped down hard. Care was taken to make sure that the key
frame didn't hold the wood cauls up in the air so as to ensure that all of the cloth is
under maximum compression. This will be left in place for at least two weeks to help
compress and stabilize the back rail cloth.
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19) The damper guide rails are sanded clean and lacquered while the old bushings are
still in place. When the lacquer dries, it will be buffed and then the old bushings
will be removed and replaced. This will guarantee that the new bushings get no
lacquer contamination in them which would result if this were done after rebushing.
It also is best to do it this way since the old bushing cloth protects the glue joint from
contamination from the lacquer as well.
20) The damper felts are soaked with water and then all the old felt and glue are
carefully scraped off. The new felts will be put on with hide glue as before so that
the new glue will bond perfectly with any glue residue that may have been left behind.
21) Replacing the action cloth on the damper lift rail.
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22 - 27) The lid was broken at one location. These pictures show the process
in which it was repaired so that the break will never again be seen. Neither will it
ever break there again. A 1/4" slot was cut in both sides of the break then a
shim was made from Delignit pin block material to fit into this slot. This style
shim has the grain running in perpendicular directions which will give strength to the
joint. The lid had broken right at an original glue joint where two panels had been
butt joined. I cleaned the old joint completely and then glued the whole thing back
together again using the shims to reinforce the joint. The assembly was clamped with
the help of the lid support struts and a large ratchet strap. The ends of the shim
and slot were run right off onto the decerative edges as well. This will keep those
areas from showing any seams in the finish as a result of flexing in the future. All
of the edges will be shaped and cleaned up after the repairs have been finished.
Then a 1" section of veneer was removed on the top and bottom of the lid right at the
glue joint. New veneer was then glued into this section with the grain running
across rather than parallel to the joint. This will add more strength to the joint
and will also ensure that no seams will ever develop in the finish at the area of the
joint. Picture #25 shows the fixture that I use to cut the replacement veneer into
the exact sizes needed. This fixture ensure that I get very straight edges and a
nice fit to the original veneer left on the lid. Picture #26 shows a flatt steal bar
that I use to sand the veneer flat and flush. In the final picture you can see the
top of the lid has had the slots cut in two places in the veneer. The smaller slot
was cut because the veneer at that point was looking slightly questionable at a joint
between two sections. Therefore, the questionable veneer was removed and
replaced. When the out layer of the veneer was removed it became apparent that the
inner sections of the veneer were in excellent condition. This piano was veneered
with a multiple layered veneer. The grain of this veneer runs in perpendicular
directions in several very thin layers. Only the out of these layers had actually
been bad.
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28 - 30) The damper guide rails on this piano were of an unusual design. It was difficult to get the exact dimension in the new bushings that will make the dampers completely free to operate and yet so tight that they don't wobble in the least. It was decided that the best route was to use a double layer of very thin high quality bushing cloth. You can see in the pictures that pins were inserted as clamping cauls as each layer was installed. You can see in the final picture that the pins/cauls are being removed in part. In order to get the best fit, it was necessary to remove the clamping pins after they had set for about one hour. This allowed the felt to spring back just a tiny bit. This helped to finalize the size of the holes to the desired dimensions. As usual, hide glue was used to glue the cloth in place. This type of glue is compatible with any glue residue that may still be inside the rails and will remelt this original glue and bond with it. Also, by using this glue, future rebuilders will find it easy to get another perfect glue joint by using hide glue again in replacing the felts. The end result was a perfect fit for the dampers.
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