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Hallo

I find it strange that from some of the polyester and laquer providers I asked, , when I say it is for pianos, many tells me that the polyester is used as an undercoat, then the final coat (high gloss) is often proposed as a black PU, that can be polished.

Only one provider told me they have a "piano" quality high gloss polyester, used only in thin coat.

I am a little lost between the different qualities (to spray vertically, to use as undercoat, etc)

I have use PU but never sprayed polyester. And I wish to be able to do so , while I dont really understand why nobody does (it must be highly toxic, I guess)

Why would you want to do that??

Polyester finishes cannot be removed. The piano cannot be refinished, which means it becomes a disposable commodity. Absolutely hate the stuff, not to mention you'll die spraying it. You need serious controlled breathing apparatus to survive.

Jim Ialeggio

Jim yes it can be done again , usually stripped with heat. But very good equipment is necessary to spray, I was just expecting to find a adequate resin, PU also is very toxic. And most of our pianos are polyester high gloss.

Chipzs are repaired, but spraying is done by specialists. Due to the reduced shelf life and high cost of products sold only in large quantities, I will leave the project for other solutions.

Buffing to new shine is one advantage of polyester

I've never understood the attraction of polyester, other than manufacturing expediancy.

I find the finish garrish, all edges become indistinct radii, and it looks like plastic...uhh, probably because it is.

Whatevahh...I guess I'm an Olde Farte on this one.

Jim Ialeggio

Sure the shine of a true black shellac is in no way compared.

Polyester is not even cheap, and not known as a good product for wood. But it is well used for boats, cars, moldings, etc...

Anyaway most of the black pianos we work on are shiny polushed polyester (plus you have to sand and buff ...)

If you can have your surfaces horizontal, you can use polyester for cars (transparent but easy to blacken) and use a simple brush to obtain your laquer. I did see a wood finished vertical Yamaha repaired that way and it was OK.

Having a medium sized grand made with new poly is around 5000 € (with new or polished logos and brass parts)

I do not like the material but I have to use it...

What is the black lacquer used on NY Steinways today ? And beforethen ?

Polyester does require a sealer, polyester based. Otherwise, the grain of the wood will ghost.

There was a period where polyester sealer was top coated with PU though I believe PU mostly did not have polyester underneath. Some epoxy surfacers and PU surfacers.

Polyester sealer is used underneath some lacquer and that lacquer is rubbed for that classic look.

One EPA consideration, polyester is a chemical cure and the % of solvents that evaporate into the air is minimal as compared to PU or lacquer.

Scratch test usually reveals type of material.

Pigment cut ratios in Lacquer and PU can be 8 to 12 ounces/gal
Polyester, as little as a tenth of that.

PU/lacquer will scratch the color of the finish.
Black Polyester will scratch white.

Thank you Larry , good tips

You think PU on polyester coating is not common, for the reasons you stated ?

Yes I am amazed by the so small quantity of dye used to have black polyester.

Good news about the solvent, the smell is not good anyway

I find it useful to be able to repair nicks and other scratches , sometime in an invisible way (a question of dye if new poly have to be incrusted)

But the shelf life is not that good , and those are expensive products.

You could use colored CA from the guitar industry.

sorry but what is CA, in that case ?

cynoacrilate
One American brand is Superglue.

CA works well for filling split bridges and even soundboards. Dyed black it can be used to repair polyester finishes.

Stewart-McDonald is one source of tinted CA and epoxy.

Thank you
Then it is a possible good tip for scratches, but nicks are often too deep to be filled , a first coat of something is necessary. I wonder how is buffed the CA it is sold in large quantities at an accepteable price ?

CA will not buff anywhere near the same as poly.

This will always show the spot.

If it is a satin poly, you have half a chance with CA.

Interestingly, CA will chemically bond with poly. Unusual as not too many things will.

Konig makes a fast cure poly system that is very useful.

You are correct Oleg, in deeper fills, poly, just as any finish, the top surface ghosts the surface immediately underneath. It is sometimes necessary to apply two separate coats or fills so that the top is reflecting a smooth base.

Yes Larry, I am using Koenig paste or resin, and it is very useful.

bubbles and color match are the main problems, parrafin on the top the one that oblige to put the 2 coats soon or to clean the parrafin.

Poly on poly really mix (as soon as the edges of the repair are thin enough.
The qualities to be sprayed induce mix of 4 different products, control on heat, moisture, time (20 minutes for the next coat)

I would have buy some bu 25 liters ... too much for me.

On very small scratches I apply the rosin with a brush directly , as a paint, sand (water sanding) finish with sanding pads 1000> 3000 on foams (I'll look for stronger grits as the surfaces are not always as flat as we wish, and machine sanding is efficient)


A common fast repair on scratches and nicks is using black copal rosin, direct shine, but does not buff well

If you click on the link "Stewart-McDonald" in my previous posting, it will take you directly to their catalog page.

Thanks Keith. We have the Cyanolit brand here with many kinds and viscosities but not much used in wood trade.

I see solvent is never used or proposed . No cleaner fluid. Too dangerous it have been a prohibited product I was said. Even accelerator is not allowed in workshops today so using it in spray....

I have seen the nicks procedure, thank you. It may be useful to have a black glue, but Koenig repair poly process is 10 times faster and melt with original poly so it is more normal to use it.

I wish to see aging and strenght test on those glues. The bond originally seem to be by adbsorbing the air, so matching surfaces are necessary, seem to me.