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Would you recommend piano teachers to use this product on their grand piano? Why and why not?

Also, what is the perfect humidity for grand piano?

Yes, and the accepteable humidity is a range, where the wood moistiture doe snot fluctuate too much.

Modern pianos accept relatively low range of moisture in winter (the wood are seasoned for modern heating today)

high level of moisture is less easy to correct, then a string cover seem to be a very good idea as it protect against dust and corrosion (it is easy to take out also)

strings are not protected against corrosion usually.
AN humidity and temperature (both are linked) range is provided by Petrof on their site. (nice complete explanations on the hygrometry question)
how to take care of my piano


but their instruments are "tropicalized' (meaning all wood surfaces are coted with moisture resistent lacquers, that does not avoid humidity penetration totally but that lessen it.

I hope that helps

Hi EzPiano,

The usefullness of a string cover is dependent on how you generally have the placement of your piano lid. It is primarily designed to keep "stuff" out of the inner cavity of a grand, meaning the strings, frame, and sounding board. Many teachers never open the lid to "full stick," and then, it would not really be needed.

What I have done is to make a smaller version out of felt, covering the area under the music desk, to protect the exposed area when the front flap of the lid is folded back. This keeps dust, paper clips, pencils, etc. from falling on the tuning pin area. Piano teachers know that paper clips *love* to wedge themselves under the strings!

About the "perfect humidity" for a piano. The manufacturers are in agreement that a Relative Humidity (RH) of 40-50% is ideal. Consistancy is the important consideration, especially across seasonal differences.

If you are thinking about a string cover for RH stability, it can often be useful when using a humidity control system attached under the piano (Dampp-Chaser). Then it is for humidity control rather than cosmetics.

The best advice would be from your piano technician to give opinion on what would best address your particular needs.

Marty . have you ever heard the term " humidity barrier" ? The numbers you give are not meaning much. You believe you know what moisture levels pianos are accepting ?

sorry to rant , but all those points are well explained for instance in the link provided. On an ancient piano the seasoning of the wood was not taking in account modern heating. on a recent one, yes

Then even the 45% intention as explained generally is meanless without a temperature. 45% in a very cold room is way too much, and in a too hot one is not enough. But it is a simplification for the main public.

on a specialized forum we may try to give precise explanations or explain why.

To me a string cover helps even if the lid stay closed : no corrosion.

The damp chaser is more for the soundboard shape and protects the pitch. A customer is since 3 years recording every 5 minutes under the piano and in the room and can attest his system is efficient (small c1 &undercover) .
another one had a failure and the Dc stopped to warm the air. as there is always something "on" with those systems logical circuitry (an old design) only the moistening was acting and permanently. after a few weeks the piano was horribly out of tune. hopefully the pianist came ( the tank was re filled by his mother) and detected immediately sluggish notes and bad out of tuneless.


Since then, I only install DC when the piano can be controlled by the owner, and I would not consider installing some kind of automation to fill the tank.

Too bad I was very confident in the product before... that hole in security refreshed me a bit... no luck may be , as this may certainly be rare. something with our 60 hz electricity again may be...

back to work

best regards

Kamin,

Oh Please......

I answered the OP's questions. I didn't go into extended theory or hypothesis which is not relevant to the questions asked.

no Marty, you wrong ! no chocolate for dinner !

Not true: No matter what temperature, 45% is a great target humidity level. A hot room at 45%RH will not be drier than a cold room at 45%RH.

A cold room at 45% RH will be more moist than a hot room at 45% RH, because warm air has a greater capacity to hold moisture is more than cold air.

that is a good way to see things may be I thinked about at reverse. a wood moisture table should provide the answer precisely, what count is the wood moisture level in the end. Indeed I was right 45 in winter without heating the wood would be more humid than if the 45 relates to a high temperature .Because air is more hygroscopic than wood.
the wood can pass from 8.75% in the cold room to 7.50 in a very hot one.

indeed that 45% number is a good medium number but but it does not make the wood at a similar moisture content .

I would say that we may aim for a wood moisture content from 7% to 10%. for instance . more for an old piano if possible. but for instance at 60% at low tem, the wood is yet at 11% moisture and attain 10,5 on a warm sunny day.

stabilizing the relative moisture level of air is of course better than nothing but trying to keep high levels in winter is unnecessary and difficult.

that provide ranges of temp/hygro that may be a little larger than we imagine usually.

The point is that RH-45% is still at 45% no matter the temperature reading. Temperature affects the RH, but an accurate reading of RH=45% will be 45% because it is recorded at a given temperature.

Consistancy of both temp. and RH will aid in the stability of the instrument.

No, because the RH is how much moisture is in the air relative to its holding capacity. The RH% already takes the temperature into consideration.

yes a little but it takes in account for the air, and that is the wood moisture that matters.

and it is not a pure percentage in air , as could be the weight of the water in the air. the HR number relates to the saturation of the air.
cold air as it cannot hold much moisture have a higher HR number for the same quantity of water, than warm air.

Those numbers can be misleading. it is not so important, as you said 45% is a good number generally speaking. but for the same temperature.

in cold air 45% mean less moisture simply because the number relate to the maximum moisture the air can adbsorb. That is not the number that is at fault that is what it express.

indeed woodworkers are more at ease with those numbers than I am. even ig I use some wood I am not building ...

The amount of moisture in the air, the Absolute Humidity, is greater in warm air than in cold air for a given Relative Humidity. I had to run out as I was posting, so what I wrote was unclear.

[quote=BDB]The amount of moisture in the air, the Absolute Humidity, is greater in warm air than in cold air for a given Relative Humidity. I had to run out as I was posting, so what I wrote was unclear.[/BDB]

I can agree with this statement. But Kamin stated above that 45% would be too low in a warm room and too little in a cold room. I was trying to convey to him that 45% is the right amount of RH whether the room is 50 degrees Fahrenheit or whether its 100 degrees Fahrenheit.

yes that is a sort of secure number indeed. unless it is near icing and having pianos in those conditions is meanless ... but the wood moisture content may vary under the different declinations of temperature at 45% RH

I've been doing a little homework and found that temperature has a fairly small effect on EMC for a given RH%.

Check out this EMC calculator: http://www.csgnetwork.com/emctablecalc.html

According to the calculator, wood at 35 degrees Fahrenheit, will have an EMC of 8.7% at 45%RH. Wood at 90 degrees Fahrenheit, will have an EMC of 8.3% at 45%RH.

Also at 70 degrees Fahrenheit, wood at 42 %RH will have an EMC of 8.0% and at 52 it shoots up to 9.6%. So you can see how much more drastic changes in RH are compared to temperature when it comes to the moisture content in the wood.

ANd there :
wood shrinkage calculator

You can have the real computation of the wood movement in radial and tangential direction, for all species.

There you can understand why the pitch change between summer and winter, particularly when you think that the level of moisture of a typical dry wood is between 7% and 10%

I am not at ease with inches but you can enter the dimension of a typical soundboard in the tangential direction, then knowing the board is fixed on its perimeter imagine how much motion you get with as small wood moves caused by 1.5 difference in moisture content.
Air saturation is at 100% , wood moisture fiber saturates at 28 %.
so the effect is not the same, and "small" numbers mean more than we think (I was surprised when I have seen those computations first time)

Best regards

Thank you for all the replies!
For the piano string cover, does it has to be felt or polyester is okay too?

I would stay with felt!

Agreed. The fact that the cover is felt is part of the protection. I don't believe a polyester would provide the same level of humidity protection.

I was not a believer in string covers for many years. Perhaps as a cosmetic thing, or to stop dust...ok...but I had my opinion changed a few years ago when I encountered a 1950's grand that had a felt string cover installed when it was delivered. That cover had been in place since day one.

I literally was astounded at how pristine and perfect the strings and soundboard were! That piano looked totally showroom fresh and clean. The felt cover was installed on hooks that were fitted to the rim of the piano; the opening in the felt for the hooks were finished like buttonholes in a shirt, with embroidery and fine detail throughout. Never seen anything like it since...but the point is this; that piano was gorgeous and clean under that felt string cover. I now believe the string covers are worth the investment.

Respectfully,
I remain,