Piano Player Repairs

Ok, so this evening I had cleaned up the piano's board, re-covered 5 of the units, and was getting ready to install number 14 as a test.

Why 14? Because I re-covered it a few days ago so the glue is dry, it's a nice working bellow, and in addition to not having anything near it (13 is off and 15 is off and there is a spacer between 14 and 15) I'd be able to gauge how well the glue is holding and remove it if necessary.

This is not the first time I tried; I did it earlier and found that the note did not play and there was a complete leak between pneumatic and piano board. Apparently putting on the glue with a brush was not enough; nothing had "squeezed through".

This time I did it different. I mixed up glue in a squeeze bottle and applied it to the pneumatic bottom in a rectangle, then put the pneumatic on, then removed it as I didn't see the "squeeze"

Hardly any glue transferred to the board. The problem was that the glue was too "thin". Upstairs I went and dumped 3 tablespoons of glue crystals in, mixed it up, and put it back in the 150f water heater.

Cleaned up the thin glue and after letting the glue warm up. This time I tested the glue and it came out much thicker. Good. I put it on the pneumatic, then pressed it onto the piano and THIS time I saw the squeeze. Held it tight for 8 minutes, then released it as it should be "set"

Yaay. I'll let it sit overnight, then try it in the morning.

Interesting. Got up this morning, ran the test roll, and note 14 played *perfectly*! No hiss, no lost air, worked!

Very happy indeed. So I melted down the glue and decided to put on pneumatic 13 and 15.

This is where it gets interesting and I wrote down the processes. In a nutshell 13 went fine, 15 was a botch, as was 8 (tried that as well)

The reason they come off is pretty apparent: Dad used over-heated glue on this specific set of 8 and the glue is crusty, hard, black, and flakes easily. My guess is it was a bad night 50 years ago.



Crunchy.....

Also it looks like he used a paper gasket between the pneumatic and the piano board, you can see it on the left. Was this in fashion in the 1970's?

Anyway, I have removed the old glue, recovered the little bellows, tested them by blowing hard and ensuring there is no air leaking, and have tried re-installing them. My Procedure is as follows:

• Mix up Thick hide glue in a squeeze bottle. Well get it from the fridge, mixed a few days ago.

• Heat glue in microwave with bottle in a cup of water, power level 4, 30 seconds at a time till almost hot to the touch

• Let sit in 50c water in my little heater pot (a wax melting pot with temp control)

• When glue hot try out on a piece of paper looking for firm bead.

• Apply bead as per John Tuttle instructions on 4 sides of the pneumatic

.

• Note: First time I did this with my first glue mixture the bead was "watery". So I added glue crystals and now bead stands up and does not run.

• Apply pneumatic to board, press hard, look for "squeeze"

• Hold pressure for 600 seconds (10 minutes)

• Release and try piano in 2 hours

Pneumatic 13 and 14 bottom level went in with no problem. Squeeze good, After 2 hours plays fine with no leak. You can see the nice squeeze at:

Pneumatic 15 did *not* have a squeeze, pulled it, the glue was not adhering to board. Put aside.

Did pneumatic 8. Once again very little "squeeze" and when I tried the piano in 2 hours I heard the hiss of air around the joint. Pulled it, glue was like gummy taffy, but none of it stuck to the board.

Pic at: (pneumatic) and


Question: What is going wrong, and why did two pneumatics installed in the same session have such different results?

Is my glue too thick? Need water?
Need more glue on the bead?
Should I sand the bottoms of the pneumatics with fine sandpaper?
Should I sand the bottom of the pneumatic board on the piano?
Should I "pre treat" the wood with a thin layer of more liquid glue (1-1 ratio water to glue) with a brush then let that set THEN put on the pneumatic with the bead of more "firm" glue? I removed the old glue because it looked like burned carbon.

This is being done in a room at 74f. As a side thought I am not comfortable with using my air heater to pre-heat the board as the air will go right into the hole and probably nuke the valves.

(Note, you can see the nice "squeeze" on 7. I think dad did them in batches of 8 a night and this was just a bad night)

Got a reply, here is the issues:

First, Never microwave glue, destroys the bonding power. Got it, won't do that again.

Second: Glue should be the consistency of warm honey. Ok, was pretty much that.

Third: This is the key bit: When gluing key pneumatics to the board, one should use a very thin layer of leather cloth between the pneumatic and the board. Glue it first to the pneumatic, wait a few hours, then glue the thing to the board.

THAT is what Dad was doing. I thought there was some kind of paper gasket; it's not paper it's thin leather. Ok, I'll order some of that but it makes a LOT more sense to have something other than pure glue between the pneumatic and the board. As a bonus, it's going to be easier to remove them again in another 50 years.

I'm learning.....