Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Verdigris in windings of bass strings. A remedy?

I've searched the forum as well as I can but can't find much in the way of a reference to verdigris in wound bass strings and, more importantly, a remedy (besides replacement). Any advice on this?

Greetings,
What many of us have done is to either dramatically loosen the string and then yank it up to pitch, or remove the string, twisting it into a coil then straightening it out, or soaking it in various treatments, ranging from alcohol to lacquer thinner, or we add twists. Everybody has their own approach.

Then we all throw them away and replace them.

Regards,

I've put a drill in a vise with a wire brush attachment and then ran the strings through, sideways, so the bristles get into the grooves.

I have cleaned a set of wound strings by soaking them in a solution of EDTA.

They came out clean as new and sounded good.

No need to replace them.

They were wound with copper.

If I were desperate I would remove the strings snd soak them in penetrating oil and coil and flex them to remove the verdigris. Then I would thoroughly clean them in an automotive product called "BrakeClean" which should remove all traces of the penetrating oil.

I have had good luck with pretty decrepit looking -- and VERY decrepit sounding -- bass strings by simply twisting them about three turns. Night and day difference.

I have had a tech attempt to polish bass strings in place with an attachment in a drill and it did not make much difference at all to the sound. I am dubious as to whether this really gets down into the windings adequately.

Don in Austin

Hemloch,
For cleaning upright bass strings we have always used a process similar to Gadzar's. The difference being that we use household ammonia rather than EDTA. I cannot seem to find a ready supply of EDTA. Ammonia is a traditional brass and copper cleaner. The aqueous ammonia they all for cleaning floors is pretty weak at about 3%. It can be used straight from the bottle, and makes a gentle chelating agent. If you would like to see how we do it, you can visit our Hampshire Piano YouTube page. The videos are pretty awkward low resolution affairs, but I hope they help.

But if by verdigris you mean a blue-green crystalline crust on the windings, they are too far gone.

Good luck,
Craig

I bought EDTA in a drugstore. Solve 200 gr of EDTA salt into 3 liters (3/4 gallon approx) of water.

Heat one half of the solution to boil.

Soak the strings in it and use a toothbrush to brush the strings until they becone clean and bright. Rinse with clear water and repeat with the other half of solution.

I used a hair drier gun to dry the strings.

In a matter of minutes you have a set of nice clean good sounding wound strings just as new.

Thanks everyone, for the good advice. Yes, the strings are quite green and very dull - worse than tubby - to play. I think in this case, to replace them will be the better option and probably no more expensive than the process of cleaning given they are from a grand piano (coils have to be removed through the agraffes etc). If I were to clean them, the ammonia or EDTA and perhaps dried in the Australian hot summer sun could be the way to go. Jamie

What does EDTA mean?

All of the above methods are far more trouble than they are worth. Simply get a soft (versus hard) wire wheel and attach it to a high speed drill (a polishing tool is even better). Loosen the damper up-stop rail and prop up the dampers as high as they will go. Then, run the wire wheel up and down the strings, perpendicular to them where you can. Avoid the plate struts. You don't have to necessarily polish every spot. You can polish the spots where the wire wheel will not reach with a Scotch Brite pad, if you choose, to make the polishing job look more complete. A Dremel tool can also reach tight spots but you will wear out the costly brushes quite quickly. The shaking of the strings will also do a lot of good. You will want to wear hearing protection. It makes a monstrous noise!. This will only take about 10-15 minutes.

If that solves the problem, fine but if the strings could still sound better, loosen each string, 3/4 a turn while pulling on the string with a gloved hand to create slack. Twist each string in the direction of the winding (counterclockwise for American made, clockwise for Asian). Give each string at least one full twist. If one twist seems easy, go for two but no more than that. The bi-chords may easily take two while the heavy single strings may resist more than one. This can be done with a small pair of Vice Grips or there is a special wound string twisting tool available from supply houses.

After each string is twisted, put on some tension while lifting the coils (two, quarter turns with the tuning hammer). You will have another 1/4 turn to go while you chip to pitch. Chip barely to pitch and then run the wire wheel again. Now, put in the action and tune roughly to pitch. Remove the action and reset the damper upstop rail. Tune up to final pitch and fine tune.

This can all be done in about one hour or so and therefore is worth the time. It will always result in some marked improvement. It will probably completely solve the problem in this case but if not entirely, will still yield a substantial improvement. It is a technique that is most useful for old strings that basically still sound good. It will usually make those sound nearly as good as new, if not entirely like new strings. In cases where strings are severely tubby or rattly, if there is not a total and complete remedy, there will at least be a remarkable improvement.

The dull sound comes from contamination where some kind of liquid has caused the copper to oxidize. That interferes with the way the string vibrates; hence the dull sound. The wire wheel and shaking of the string removes the contamination and shakes out dirt and corrosion. That is why it works and works very well in amount of time that makes it worthwhile. I am surprised that most other piano technicians do not seem to know about this technique.

I would be very wary about exposing wound strings to virtually any kind of liquid. Taking the strings completely off and doing anything with them at all would take many times over the amount of time it takes to do what I have suggested.

If you are reconditioning either an old grand or upright and new wound strings is not in the budget, you can take the opportunity to put the tails of the wound strings on a wire, move them out of the way, clean the soundboard underneath the strings and polish the plain wire strings that go under the wound strings. You can greatly improve both the sound and appearance of an older piano which does not merit full rebuilding by using these techniques.

You certain its verdigris and not copper oxidation?

Verdigris is just another name for copper oxidation:

https://en.wikipedia.org/wiki/Verdigris

The sticky, oozing gunk that forms in piano flanges is the result of copper oxidation as well as other contaminants.

Thanks Bill, a comprehensive description of a very viable and economic remedy.

The oxidation on the all copper bass string windings is likely caused by exposure to excessive moisture, on flanges and brass centers that are an alloy the cause can be a chemical reaction caused by the wrong lube.
Verdigris is a different word because it describes different stuff. If verdigris was on the bass strings your remedy would be different.

It's clear from the Wikipedia article that Verdigris is not the result of copper oxidation. The result of copper oxidation is copper oxide, and Verdigris is the name given to a number of compounds of copper, but not copper oxide.

Verdigris is the result of various more complicated chemical reactions between copper and other elements, some of which, as in copper carbonate, do in fact include oxygen:

Verdigris is what makes copper roofs green, rather than black (if they were copper II oxide). Coins go brown usually, though, which is mainly copper I oxide. Copper carbonate, and many other copper compounds, are green.

Paul.

If copper combines with oxygen and other elements to form a compound or salt, green or otherwise, it the process still called oxidation?

Technically "oxidation" is the transfer of electrons. So the formation of copper chloride is also an oxidation reaction, with chlorine being the oxidizing agent. So if the copper loses electrons (and gains a charge of +1 or +2), then it has been oxidized.

Paul.

Only when the electrons are transferred from OXGYEN atoms to the other element, forming an OXIDE of the other element.