Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum repainting harp: what was ORIGINAL paint chemistry?

I've posted a couple times. I've got this 1936 kimball grand piano.
On the advice of a number of people, this thing is snowballing, and I'm going a little further than I originally planned, BUT, I'm going to be removing the strings tonight, and removing the plate tomorrow.

The plate/harp has rust damage on the pinblock end, and I'm going to repaint the whole thing. I've read some past posts on the subject, and I have 3 options:

1) DIY with spray paint in a can (do not have hvlp gun and compressor-- and won't be buying one)

2) autobody paint? basecoat/clearcoat polyurethane could look fantastic

3) powder coating?


First question is, what is the original paint? I know it's a bronze/brass powder of course --it's turning green, as a dead giveaway for one-- but what holds it together?

I need to know for two options.
First, if it's OK to wire wheel the whole thing and what's still firmly stuck on, leave on? Because if I put polyurethane auto paint on top, I do not want it to peel. If the original paint is going to interact just fine left underneath auto paint, cool! If the auto paint is not going to bind,

Second, I need to know what solvent from lowes is going to efficiently strip it off.

And I need to know about the filler under the paint. If I do strip off all the paint, I read in another thread here a warning that the original cast iron was NOT smooth, and that a filler would have been used to gloss over the rough pitting that is simply the nature of most cast iron.

I need to know that a finer wire wheel won't just cut away all the filler?
I need to know that whatever solvent I use to strip the paint, won't also dissolve this filler-- or that once I remove the paint, the auto body paint will play nice with the exposed filler material. I suspect it won't be bondo. (when was bondo invented...)

I guess the same questions apply if I were to opt for powder coating. I don't know much about powder coating. I think it's just a plastic that is heat-cured (which might mess with the underlying paint a lot if I don't get it all off?), but then I think i've also heard enamels (glass based) referred to as powder coatings too.

Personally I would not strip a plate.
You may run into more trouble than you want.
Underneath the finish they can use stuff to level and flatten the casting and if it is there you do not want to get into it.
A wire wheel will dig into the finish and give you more work filling and making it flat.
It is better to clean it with TSP then remove the rust and paint that flakes, fill the dings and scratches with Bondo and sand flat.
Then put color on followed by clear.
You should test for interference with your all of your new products by what you intend to cover before you commit to coating the entire thing.
I like to clean and prep the plate as described above then apply a seal coat (call it insurance) then some primer. Primer is easy to sand and get flat. Then color and then clear. You can then choose products that are compatible with the seal coat.
If you have not used bronzing powders before I would advise you to use one of the spray paints that come pre-mixed.
Applying bronze powder for color using a clear lacquer, then getting a good clear coat over it will take you quite a bit of experimenting without someone to coach you.

Well I wouldn't use powder coating on anything that might flex. You can get an electric HVLP gun as in single stage for 300 bucks or so. Earlex makes a nice one which I have but we only use it for primer.

If you are leaving the plate in I just normally use a 2 oz cup on my gun with an automotive acrylic enamel but the spray pattern can be adjusted to 1/16th of an inch. If you want glossy you add hardener if not you don't add any. I have used spray cans before but you will want to use 320 grit or higher sand paper not anything coarser or you will get scratch marks.

I wouldn't use chemical strippers or sand blasting as that produces heat. Look into soda blasting if you have to do it. It can be done in the piano if you have a nice shop vac. baking soda removes the grime/grease and cleans the surface yet produces no heat, doesn't harm plated parts or glass.

That black stuff you are thinking is filler is actually glass slag from the casting process, you will never get it all off. If you are trying to smooth it out you will have to use a die-grinder with some sanding discs camloc style or something.

I won't be buying a $300 spray gun, because this is a one-time-only thing.

Do you advise leaving the plate in?

If I remove it, do I risk its not aligning on reinstall, or the pinblock warping once it's no longer bolted to the plate?

On the other hand, removing it means I can clean and seal any rust on the back side (I can feel some)
It also means NO risk of accidentally spraying the soundboard; although if I leave it installed naturally I'll be careful and thorough with my masking and taping!

Hmm, TSP cleaner you say? I'll try to track it down at lowes/walmart/sherwin williams.
Where the pin blocks go in definitely collected some humidity. If a wire brush isn't recommended, then a random orbital sander and some 220 grit sandpaper? Something will have to genuinely cut through the rust, or paint won't stick very well.

If I remove it and go with autobody paint, I'd likely just take it to a car paint shop. Their labor and facilities will be cheaper than my buying a spray gun and hoping leaves don't get into the finish. Their labor might not be that bad, as there's nothing to have to tape off (a lot of the labor that goes into auto repair), and no dents to pull out either! Just a quick spray if I do the preparation work.

Take the plate out, or at least, lift it up so you can mask off the rest of the piano so it does not catch any overspray. You can lift it to the top of the rim and put boards under it to hold it above the rim. Be very careful! Lifting something that heavy and unwieldy is dangerous! Watch your hands! Make sure that if the plate drops, it will not crush them against anything!

Removing the plate will also give you the opportunity to inspect the pin block for damage. Any moisture that has gotten through to it will potentially ruin it. Make sure you do not get liquids on it when you clean it.

Clean the plate as best you can. There are a variety of household cleaners that you can use.

Spray cans will work fine. A clear coat is redundant, because metallic paint is just a clear finish with powder in it.

If you want to do a first class job, remove the plate.
It will take quite an effort to mask off everything if you do it in the piano.
What will you do about the dampers?? Do you have any experience??
You can take measurements and make up jigs that register the plate to the case so that it goes back in exactly the way it comes out.
You can buy a good enough spray gun from Harbor Freight for $30.00 to $50.00 - a touch up gun would probably work ok.
I sand by hand but whatever you come up with - anything too coarse will give you something to fill later, scratches will become visible later in the process.
TSP takes off dirt, oil, grease etc. for rust - try naval jelly??? before TSP Then dry the plate with compressed air.
Are there bushings in the tuning pin holes? Does the plate have agraffes???
Removing agraffes is necessary - take them out and polish inside and out - remove burrs from string holes - without experience you may have height and alignment issues when reassembling. You will need a agraffe wrench.
If you take it to an auto paint shop you should not let finish build up in these holes.

I'll remove the plate. I'll get 3 strong guys and be careful, with room around the piano to maneuver it. Also-- the piano is in the living room. I'd rather not fumigate the house! All the more reason to remove it.

I've been warned that damper alignment is among the hardest... let's say most fickle? jobs. I have someone who is going to instruct me, and reblitz' book. He is also loaning me some of the specialized tools for the day or three that I need each of them, which is awesome.

Tell me, are there any markings I should make on the damper posts before I loosen the set screws? Even if it's just a permanent marker to draw a line at the right height, or wrap some masking tape around the wire post as a depth marker. That said, there's a real chance I might opt to replace the felts anyway, which would change the heights.

I'm really hoping the pin block is in excellent and reusable condition. I'll find out! For the moment I have every reason to believe that it is still in good shape. What sort of things could I do that would damage it? (to be careful of). You've mentioned not to spill liquid cleaners on it. Anything else, before I proceed?

What sort of measurements/jigs? I just assumed that the screw holes WERE what aligned the plate into the case, and was just going to lift it out without any alignment marks...! If the scress are perfectly aligned between the holes in the case and the holes in the plate, why, it should align itself! But if this is not in fact true, let me know what you like to do, to do it right.

Hmm. Naval jelly is surprisingly expensive, but I believe I have a jar already if I can find it! It's useful because it can actually reverse surface rust to a limited degree-- revert it back to metal.

There are bushings in the tuning pin holes. Do they need to be removed? Do they need to be replaced with "3/0" compatible bushings? (I am going up a size from 2/0 to 3/0).
Otherwise, the easy way to keep paint out of the bushings of course, is to drop all the original pins back into place Maybe a *very* light tap to just get them to seal. That will keep the paint out. When I painted my engine block, I just put junk spark plugs into the spark plug holes to achieve the same solution (keeping paint out of holes).

There are agraffes. I've been warned that they are brass and easy to break off. None look damaged to warrant replacing. I will clean them with a dremel-scaled wire wheel, and wrap them around with masking tape. That will save the holes, too. I'm wondering-- a couple of them, as originally installed, are sitting maybe a degree off at a different angle from its neighbor. Is this as designed, or does it even matter, or should I tweak these couple back into perfect alignment?

For dampers you may want to make a jig that lifts the damper lift tray so that it just barely touches/supports the damper lift levers and leave it that way - make the jig so it will not move - then when you put the damper wires back in to the levers the height will be close enough to what it was, leaving you with alignment.
The plate screw holes should give you left to right alignment and the block itself will give front height registrations. If you believe that is good enough then you do not need to take any plate to case measurements or make any jigs for registration. The dowel supports that you will find under the plate bosses should give you the height of the rear of the plate, if they are damaged from torquing the plate screws - that is another story - good reason to take bearing measurements before tare down.
I would remove the bushings - plan on new ones. If you put in pins you still get paint on the surface and it looks amateurish.
Masking the agraffes may also give you less than satisfactory results.
The alignment of the agraffe should be the best right angle to the strings of the unison that you can make - it helps with equal string length and unison tuning.

Local bodyman will do 2 stage professional polyurethane paint for $210. Does that sound fair, or shop around?
Spray can paint is much much cheaper (like $20 for 8 cans), but then, this might look so much better.

I have a couple last questions (I'm about about done though).

The BOTTOM of the soundboard where it mates to the plate (there is no capo d'astro bar to matter),
can/should this get painted too, or will that effectively shim the plate up by enough thickness to change a dimension for the worse?
I'd prefer to paint it to keep it from ever rusting again,
But I need to know if I then need to level it gently with a sanding block by hand,
Or also if I need to keep it to a minimum (like, one stage of clear coat-- instead of the 4 layers that are going on the top!).

How fragile is the plate? Can cast iron even warp over the short term? Obviously I won't be dropping it onto any cement of course!
But the question is to ask: can I put my 4.5' wide piano plate in the back of my 4' wide pickup truck at an angle, leaning against the side (cushioned with just a little blanket), or does it really need to lay completely flat in say a rather wider trailer? An actually rather severe inconvenience to rent one for two separate days, but I'll do what's necessary, if it is necessary.

Final question just to be sure I understand.
I now know what downbearing is, and will be measuring it in several spots before I ever remove the plate.
What I know from working on cars is this-- that metal isn't very flexible, and every bolt bottoms out first, then torque readings are just to stretch the bolt out like a rubber band for more and more clamping force as you torque it further.
For something like an oil pan or valve cover, there's cork or rubber in between that can get crushed if you're not careful, squeezing it out of the gap and then it leaks. More torque isn't better.

In a piano you can crush the wood that is under the plate if you overtorque.
So does reinstallation of the plate work like this:
Lay it in place
zip every screw down until it's just starting to bottom out.
gently start torquing them down in an even criss crossing sequence
measure the downbearing as I go, in all my little spots, and where it's not enough downbearing yet, just turn the closest screws a little further until it is. Stop when it's back to where it was originally in all spots. Back off if I accidentally go too far (and make sure it sprung back! if it stays at a high downbearing, I crushed something?)

There was a craigslist piano right now where the guy said, among other light maintenance done, that he took the time to 'increase downbearing.'
is this a thing, that can be done to change tone (tightening all the screws)-- or does it mean that he naively did something wrong to his piano?

also, is the pinblock only held to the plate, or is it bolted to the case as well?
That is to say, when I remove the plate:pinblock screws, is the pinblock going to drop violently and I should prepare to support it?

Once I remove all the screws that hold the plate in, should it just lift right off (well-- slide it out to the back with 4 strong people. 'lift right off' is relative)-- or are there any other final details to be aware of?

Little by little the job gets bigger and bigger.

If your not planing on doing extensive sound-board work make sure it's good enough to produce a nice tone or you may end up disappointed with the end results.

When painting the plate of this Kimball I'm attempting to re-build.

I first removed the old clear shellac which had darkened with denatured alcohol.


I removed all the agraffes, kept them in order on a piece of wood.
Then filled the small dents and scratches with auto scratch filler.

I purchased six different types of gold spray paint and ended up choosing a lacquer based one I liked.

After spraying the gold I sanded with 320 grit and put a couple of layers of clear lacquer over the gold.

I then wet sanded with 320 grit sand paper and than polished with compound.

The agraffes I cleaned with a wire wheel. After mounting them back on the plate I gave them a light coat of lacquer.

The BOTTOM of the soundboard where it mates to the plate????
_____________________________________________________________________________________________
Iron plates will flex but they will crack if you go too far. My guess is that if you wrap it in a moving blanket and secure it so it does not bounce around It should be ok.

If the plate goes back in exactly the way it came out the bearing should be ok. If I were you I would not mess with bearing. It wont hurt to measure and record however.

It won't hurt to torque the plate bolts in a pattern - I would put the plate screws on a wire wheel and clean up not only the head but the underside on the taper. When you start torquing the screws into new plate paint it will help avoid pulling it up. Don't over torque especially in the rear area where the plate is supported by wood dowels - it helps to have clean screw threads, clean out the hole and put a bit of teflon powder or bees wax on the threads so that you have a better feeling of what is happening. Don't strip or cross thread. Just snug so the plate boss is firmly seated on the dowels for the rear and a bit more torque for the screws on the pin block.

Photos help but usually the block is doweled and or glued onto shelves cut into the rim - it may be glued onto the stretcher as well. It should not fall out but no guarantees.

If I were you I would make a cardboard pattern that can keep your plate screws organized - it can be a puzzle if they get mixed up.

Thanks for the advice woodfab! That looks exactly like my plate-- only cleaner Yours looks great. Hopefully mine will in a few days, too!
Yeah, it does get bigger and bigger. Projects always do-- am I surprised? I think I'm cutting this project off at its present dimensions however.
What year is yours? Would my 1936 also have shellac as a clearcoat over the bronze?

It's hard to say about the soundboard. It's actually in good COSMETIC condition and has an arch. Tone? Well, the piano is missing a dozen strings and the rest haven't been tuned since 1960, and all are original to 1936. Very hard for me, no connoisseur, to say how much is soundboard, and how much is the godawful condition of the strings or deficiencies in the action.

Good call Nelson about using more old cardboard boxes to organize the plate screws and agraffes. My dampers are already in a neat line.
A lesson I learned early when I did my first water pump! Two dozen bolts and it took literal hours longer to figure out which went where. I think some of them might still be wrong.

Yes, I'm asking about the bottom of the soundboard where it makes to the plate.
When I wrap my fingers around (where the bass strings are absent), I can feel that it is rusty under there! Of course I can't reach to the pinblock, and until I remove the plate tomorrow I won't know how it looks right at that surface where it goes over the pinblock. But inches in front of the pinblock, it feels already mildly pitted, which is a concern!
But naturally it's a concern, if rust is wedging itself between the plate and the pinblock (rust takes up more volume). When I clean it up and paint the underside where it mates to the pinblock, how machinist-exacting do I need to strive to be? Or would a few microns thickness of paint, provided no bubbles or drips, be A-OK? Especially on this surface I will go easy on the sandpaper. The last thing I want to do is grind hills and valleys into that particular surface (i suspect).

!932
It was on it's way to the dump when I rescued it.

Now after three years it's almost done.



PianoWorld and members willing to take time to share their knowledge has been so great.

"Thanks"

Wow, nice job Dan! Thanks for sharing the success story.

Best wishes-

Yes indeed! I can only hope that mine turns out half as clean when I'm done with it.

I may leave more of the original finish in place however, so mine sadly will not have the rich full gloss that you have given yours.

I will be painting my plate tomorrow! Just have to finish a few more things tonight.

I decided you guys were right, and went ahead and removed the agraffes. If you saw the photos of the plate rust, there is just no way I will do a decent job with them still in place. I took a photo of each section to use when reinstalling, to get the angle right. Happily, despite all the warnings about being frozen and breaking off, they all came out with only half as much trouble as just a pickle jar lid. Even with just a crescent wrench. Would you believe that not a single technician in iowa city has an agraffe removal tool? Guess it's just not common to do them, and when you do, a crescent wrench suffices.
Can I at least reuse the agraffes I have? (undamaged). Or have I committed to buying a fresh set now, by removing the old ones?

As it stands I will paint the plate with the tuning pin bushings still in place. I still am not clear on this point: when I move up to 3/0 pins, will I need to replacing the bushings, or can I leave the existing ones in just fine?

Do not paint the tuning pin bushings. Take them out and order new ones that match the same depth as the old. If you leave the old ones in and paint them, expect them to look like crap once you start driving tuning pins through them. The paint will crack, and probably chip the new paint from the plate. (I'm also hoping you measured the plain wire strings so you replace them with the correct gauge wire...and that you measured each tuning pin as it was removed, to be sure there are no discrepancies...)