How to fix paint cracks on plate?

Posted by: AB

How to fix paint cracks on plate? - 03/04/13 02:07 PM

Dear piano restorers,

Is there any way to fix small paint cracks that have developed in the gold guilding of the plate? I was told that short of stripping and reguilding, which would necessitate a new pin block and restringing it will always be a visible and imperfect repair. Some people call this "cold checking" even though this may also stem from too many paint layers. This unfortunately happened in our newly restored 1888 Steinway C. It should be a warranty case but I dread the time factor..

Thanks!
Posted by: Nash. Piano Rescue

Re: How to fix paint cracks on plate? - 03/04/13 05:51 PM

One of the things I notice about piano plate re-guilding is what type of stripping method are they using before re-painting the plate.

Many old piano plates have a glass slag stuck on them from the original sand casting process. This comes from dry sand melting from the molten iron. so when you see little cracks in the paint that is usually what it is. That slag coating has cracked somewhere.

Whenever I have to strip one I make sure to Magna-Flux the bare casting to see if I missed something. Unless the builder does his own stripping that can be a big deal if the blasting company dropped the plate.

It is possible that the painter didn't add a flex agent to the paint if it was done in the colder months too. I have painted a few plates in the piano when the customer had a small budget but it's a masking nightmare and it doesn't look as good as taking the plate out.
Posted by: Olek

Re: How to fix paint cracks on plate? - 03/04/13 07:02 PM

are not the plate sand blasted to clean them before painting the undercoat ?

On some old plate the gliding was done with gold leaf, and the red product under there is the one that allow the gold to stick well

there are some special paints used to repair golded furniture, water based (plus minerals) they can be mixed, then a clear coat of laquer added. I always keep some gold paint when spraying a plate,it is easier than making the mix later (varnish plus bronze powder) Modern sundboard laquer is good for plates I was said, good flow and good leveling.
But plates are easy to spray (less easy to sand !)
Posted by: accordeur

Re: How to fix paint cracks on plate? - 03/04/13 07:18 PM

To the OP,

Find out what the colour and product the rebuilder used if you can. A good touch-up person can make it really nice, depending on the location and difficulty of access.

You do know that it does not affect the sound?

If you could post pictures would be most helpful.

All the best.
Posted by: BDB

Re: How to fix paint cracks on plate? - 03/04/13 08:25 PM

These things patch up nearly invisibly if you can get bit of the paint that was used. Metallic paint blends very easily.
Posted by: Olek

Re: How to fix paint cracks on plate? - 03/05/13 06:02 AM

the metal paint is +- the easy part if you can have the good powder, but on most pianos a clear coat is added, direct shine, not buffed.

Steinways are not covered with a final clear coat, so they are easier to correct.

Usual plate paint is very similar to cars, with an undercoat (white, red, depending of the final colour expected) sprayed sparingly with a black spray so you can see the quality of the water sanding (the black paint shows where the holes are)

then a red primer if the undercoat color is not the one wanted.

The main problem is to allow everything to dry enough, polyester primer can hold water.

A plate gliding, well done, is somehow expensive due to the long prep job
Posted by: AB

Re: How to fix paint cracks on plate? - 03/05/13 11:06 PM

Thanks for the tips guys, I will discuss them with the responsible party.