Clear varnish/lacquer of 1960s-70s prone to hairline cracks?

Posted by: Mark R.

Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/07/11 09:39 AM

Dear technicians and rebuilders,

The finish on my 1970 Ibach shows fine hairline cracks. My parents have a similar instrument from 1966. On both pianos, the varnish/lacquer has deteriorated, showing hairline cracks such as can be seen here, inside and just to the left and right of the flash reflection (the self-made tool is just for scale, it's about 4" long):



One can feel the hairline cracks, i.e. the varnish/lacquer lifts off the wood slightly on the edges of the cracks. On both instruments, the deterioration is much worse on the side that faced the window, even though both pianos never received any direct sunlight.

Is this type of cracking typical for the varnishes/lacquers of that time? Can it be remedied/improved, without a complete strip and re-finish, e.g. by fine (wet) sanding and polishing?

Perhaps this problem is specific to the coatings used here in South Africa, but I would imagine that similar coatings were used all around the world, so perhaps you've seen it as well, and can give me some pointers?
Posted by: meadpiano

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/07/11 11:24 AM

I wouldn't think you can wet sand it! If the cracks turn yellow you can use tung oil on it to soak in to them a bit and it will dry there so they don't reappear a few weeks later. If you get all the wax buildup off some people claim you can brush on laquer thinner and let it dry and it will melt the finish back together. The problem is if you do something do it were it can't be seen! You will not know if anything will work unless you try on the piano itself. I think the finish looks fine like it is and I would not want to refinish it at all. Above all I would suggest finding a good furniture refinisher were you live and go talk to them about it and hopefully they can lead you in the right direction! Oh, and that can happen here in the U.S. too! I see it mostly on older instruments, say from the 40's 50's era. I have seen it happen more on guitars than pianos because (correct me if I am wrong anyone) it is caused *mostly* by harsh temp changes and that can happen often with "portable" instuments.

-Daniel
Posted by: pianobroker

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/07/11 02:00 PM

Can't quite tell for sure but it looks to me the existing finish had "dropped" not just cracked or crazed over the years. The cracks seem to follow the grain somewhat.Was it originally an open pore finish ? or did it over the years become open pored ?.One could possibly build the finish up but what for ? Wetsanding and shooting clear over OLDER existing crazing lacquer can be done but it doesn't usually last long term especially if the finish has dried out. Unfortunately it is like cancer, The old lacquer will work it's way through if you don't strip it down to the wood. Not an expert but have facilitated hundreds of refinish jobs over the years.
Posted by: Mark R.

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/07/11 02:59 PM

Daniel:

Wax buildup is definitely an issue. When I bought the instrument, I could smell and feel all the (furniture) wax that the previous owner had applied over the years. As far as the appearance is concerned: the photo is not really representative. There are some spots on the piano that look much, much worse in real life. Thanks for the idea of speaking directly to a refinisher.

Pianobroker:

Yes, the cracks follow the grain - although, in some places, there are cross-grain cracks as well, e.g. on the keyslip. As far as I can make out from areas that are better preserved (e.g. inside of top lid), the finish was originally close-pored, but satin (not glossy). It seems it became open-pored over the years.
Posted by: Mark R.

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/08/11 02:30 AM

Here are two more pictures that show the condition of the finish more realistically (note that these are macro photos, taken at about 4 to 6" focal distance, to show what you would see on really close inspection):

Towards the top end of the left side wall:


Key slip and part of keybed (detail crop from larger picture):


From a distance, one or two yards away, the piano looks reasonable for its age, but on close inspection, and touch, the finish is quite cracked. On the inside of panels, the finish is crack-free, but in many places it has turned yellowish and/or slightly milky/opaque.

It's not an urgent issue, though, because the sound and touch of the instrument counts much more in my books - that's why I bought it. I just wanted to gather some opinions on the finish.
Posted by: Silverwood Pianos

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/08/11 11:57 AM


Originally Posted By: Mark R.
On both instruments, the deterioration is much worse on the side that faced the window, even though both pianos never received any direct sunlight.


And this first photo is the perfect example of what UV light and heat exchange does to a finish over time. Even though the cabinet did not receive any direct sunlight the UV is still very damaging. The window placement also adds the heat component of sunlight even when cloudy. Part of this deterioration comes from the expansion of the wood underneath the finish; the wood expands more than the finish actually does; hard shell finishes like lacquer do not like to expand and contract; the cupping of the old finish from crack to crack is evidence of heat application……….

Originally Posted By: Mark R.

Is this type of cracking typical for the varnishes/lacquers of that time? Can it be remedied/improved, without a complete strip and re-finish, e.g. by fine (wet) sanding and polishing?


Wet sanding will make more of a mess than a fix. The moisture will creep into the crack lines and do further damage by lifting more of the old finish away. Early lacquers had the problem of yellowing with age. Some lacquers still have this as a symptom but now with more acrylic compounds in the mix this problem has all but disappeared………….

From the second picture, two reasons for that; one would be the aforementioned sunlight/UV damage; secondly,heat would cause the colour to expand along with the wood much more readily than the clear top coat.

3rd photo; for the lacquer you have there the long crack lines would be too much catalyst in the mix but more likely the incorrect mix of shellac/lacquer. I know that in the early 60’s European companies like Grotrian and others were using a nitro/shellac mix that was sprayed and rubbed out after. If too much shellac was used the mix became too brittle in the end resulting in cracking.

You can mix up a solution of nitro lacquer and solvent (in German it is called Bensoel or something like that (a mix of nitro and cellulosic solvent with a little bit of lacquer to build body).This is used on a piece of rubber covered with deer skin. There is so much damage however that this melting of the old finish and rubbing out slowly (no heat) will only last 5 years maybe. Then the whole thing will peel like an orange. The problem is instability; once top coated with whatever process you use, the base remains separated from the wood.

Best to rip it all off and start from scratch.
Posted by: kpembrook

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/08/11 01:46 PM

What your close-up photos show is known as "crazing".

In one sense it is "normal" in that a rigid film that has a moving substrate will eventually do this. It may be that film thickness was excessive, as well. If it shows up early (days or months after application) it may mean that subsequent coats were sprayed on too soon or coats were sprayed on too thick.

Modern (as in 2011) finishes can be expected to do this in 40 years, too. In fact, nitrocellulose may do better than acrylic lacquer because the acrylic tends to be more rigid. The thick polyester finishes resist this by being much thicker and stronger but it, too, will eventually succumb.

There is no reliable "fix". The finish is failing and after this many years, the piece needs to be refinished.

Posted by: Silverwood Pianos

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/10/11 02:18 PM


I believe that Steinway still uses nitrocellulose lacquers today, not sure really. Actually I have been thinking of switching back to nitro; some of the catalyzed and pre-cat lacquers can be finicky to use….

Regarding poly finishes, I should dig out the original photos of my Blüthner when it came in. The trouble is they are old 35mm photos; I would have to scan them or something. The poly back then used in E. German had way too much catalyst; the lid had long crack lines very much like cracks in pond ice. Then on the ocean front window side, the flat side of the grand had crazed so much it tore all of the veneer away right to the base wood. It was, however, a way to find out that this Blüthner was constructed with real wood panels instead of the MDF nonsense along with the discovery of a way to remove poly completely by stripping it off. Sometimes you can use the old poly as a base for lacquer over top but not in this case.
Posted by: Rod Verhnjak

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/10/11 02:36 PM

Originally Posted By: Silverwood Pianos

I believe that Steinway still uses nitrocellulose lacquers today, not sure really. Actually I have been thinking of switching back to nitro; some of the catalyzed and pre-cat lacquers can be finicky to use….



Steinway New York still use nitrocellulose lacquers.
I also use a traditional nitro lacquer. We have been sold some modern lacquers in the past that just don't work the way the old lacquers use to.
We now have found a traditional lacquer that works well, builds over paste filler and rubs out for satin finishes.
I'm also staying away from any Vinyl sealer as we have had problems with adhesion.

Sometimes we are told to purchase products for suppliers because it's what they have not necessarily because it is what will work best.

So many of the new lacquers today are made for open grain fishes and fewer coats.

I also want a lacquer I can strip off years from now and touch up Especially on cabinet parts that have carvings.

I dread the day when what I use is no longer avaliable unless the manufactures come up with something that works.

I'm just happy to have finally found something that works after a few troublesome trials with products that are best for kitchen cabinets.
Posted by: Mark R.

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/10/11 03:20 PM

Originally Posted By: Silverwood Pianos
Then on the ocean front window side, the flat side of the grand had crazed so much it tore all of the veneer away right to the base wood.


Dan,

I may come back to you on this point, because the lower front panel (kneeboard?) on my Ibach has done exactly this on its lower edge, where it rests on the toe-rail. It almost looks as though the lowest 2" of the panel was left standing in water... But the inside of the panel, as well as the toe-rail itself, are fine.

Originally Posted By: Rod Verhnjak
So many of the new lacquers today are made for open grain fishes and fewer coats.


Rod,
Do I understand correctly that your preferred finish (or "the" preferred finish) for a piano is open grained? [EDIT: sorry, that should read: is your preferred finish (or "the" preferred finish) for a piano CLOSE grained?]
Posted by: Rod Verhnjak

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/10/11 04:50 PM

Originally Posted By: Mark R.
Originally Posted By: Rod Verhnjak
So many of the new lacquers today are made for open grain fishes and fewer coats.


Rod,
Do I understand correctly that your preferred finish (or "the" preferred finish) for a piano is open grained? [EDIT: sorry, that should read: is your preferred finish (or "the" preferred finish) for a piano CLOSE grained?]



My preferred finish is a grain filled finish. This is what was done in the days gone by. That is what we do today unless a client wants to save some money.
Posted by: Mark R.

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/11/11 03:38 AM

Thanks, Rod, that got me reading. Hitherto, I wasn't aware that grain could be filled with anything else than the varnish/coat itself.
Posted by: Rod Verhnjak

Re: Clear varnish/lacquer of 1960s-70s prone to hairline cracks? - 02/11/11 12:03 PM

Filling with sanding sealer, lacquer or varnish will only cause you trouble.
A quality paste filler is the way to go.