DIY calibration of the Omega’s hygrometer

I finally got around to calibrating the hygrometer in my Omega. Hygrometers are typically calibrated once a year, but it has been suggested that the analog ones (like the Omega’s Barigo model .1748 unit) should be calibrated every time they are moved to a new location. In any case, I had reason to suspect that the reading was off.

The basic technique is to place the hygrometer into a chamber in which the RH is known to be at 100%. The indicator needle is then adjusted so that it point to the 100% mark.

My humidification chamber comprised a deep bowl lined on the bottom with a wet hand towel, covered by a wet (but not dripping) hand towel. The hygrometer was placed face-down on the towel in the bowl, and left for about 30 minutes. When I returned and took the hygrometer out of the bowl the indicator needle was reading past 100%.

To adjust the position of the indicator, a broad-ish screwdriver was inserted into the slot visible through the centre hole (of eight) on the rear of the case, and turned. The mechanism was pretty stiff and it took quite a bit of force to move it. I also tapped the case of the hygrometer after each tweak in order to get the indicator needle to settle in the new position. The hygrometer reacts to changes in RH within 15 to 20 seconds of any change, which makes fine adjustment of the indicator pretty difficult. It took me a couple of hours of repeated humidify/adjust cycles before I was satisfied with the result.

I then left the hygrometer on the shelf with my two other digital hygrometers for a couple of hours, to check if all were in agreement (they were, within about 1% RH) and to allow moisture condensation inside the case of the hygrometer to evaporate.

Two major piano tweaks

Fortunately (or unfortunately, depending on how you look at it) for those with piano OCD, there are not that many tweaks you can do yourself to your piano. Of course, if you happen to also be a tech, then you can regulate, tune and voice your piano until there is physically no further improvement possible.

But there are two major piano tweaks that you can consider, if you really really think that you can’t live with your piano in its present condition.

Wapin Bridge

The Wapin bridge is actually a re-work of your piano’s existing bridge’s pins. Practically all piano manufacturers angle the bridge pins slightly in towards the strings. This is to ‘trap’ the strings so that string vibrations don’t cause the strings to gradually work their way up and off the pins over time.

The Wapin system replaces the angled pins with vertical pins. It is claimed that by using vertical pins the strings are allowed to vibrate more freely, giving clearer fundamentals and partials, and longer sustain. An angled third pin is inserted between the two usual pins to provide the required string trapping.

Stanwood Precision TouchDesign

In this tweak, the action for each note is analysed and then adjusted so that the touch is ultra-even across the keyboard, with static and dynamic touchweights set to what you want. The action parts for each note are weighed and measured, and the geometry analysed. Minute adjustments to the weights of individual parts and to the geometry are done, and the friction of the action centres are normalised. Here are the ‘before’ and ‘after’ weight and friction graphs of one particular piano.

Whether or not either of these tweaks are meaningful in a high-end piano is subjective, and also subject to the law of diminishing returns. This is somewhat like high-end hifi. How much are you willing to pay to squeeze the last iota of performance out of your system, and can you even hear it? I’m not saying that these two tweaks don’t work. In fact, I think that they do. What I question is whether or not they make me a better pianist.

Caring for the piano’s finish

See here for finish care guidelines from the Piano Technicians Guild (PTG).

Most pianos that are sold have cases finished either partially or completely in black polyester high-gloss finish. This is very similar to the finish that you find on cars. Although the finish is very durable and relatively easy to keep clean it is still susceptible to being scratched, it takes fingerprints (but not as bad as a black polyester satin finish), and does tend to attract some household dust.

There have been threads on Pianoworld from time to time, asking what cleaners can be used to make a black poly finish easier to keep clean. There are a couple of made-for-piano cleaners and polishes that you can buy, but I’ve not seen any of them in Singapore (maybe because I didn’t look hard enough). What you must not use are the typical off-the-shelf furniture polishes, especially those containing silicone.

What I prefer personally is to use a carnauba wax. The highest quality (and most expensive) car waxes all contain carnauba. The one I use is Blitz Wax, from One Grand.

It is a paste wax, and easy to apply — just wipe on sparingly, allow to haze, then wipe off and buff lightly. Liquid waxes are too easy to drip and spill. The tiny bit of flaky residue (if you apply too much wax) is easy to clean up with Kao Magiclean floor wipes. Residue in crevices can be easily removed with a soft toothbrush and vacuum cleaner or a vacuum cleaner with brush attachment. The wax layer is just a few molecules thick, barely 0.000025mm. But the result is a lustrous and deep, ‘wet look’ gloss that only gets better looking with each layer that you apply.

Once the wax has cured it forms a very hard protective layer (harder than concrete) over the black poly finish. It is very difficult to scratch, doesn’t take smudges easily so fingerprints don’t show, it doesn’t attract dust, and is super easy to clean. It is also easy to remove with the appropriate solvents (which don’t damage the underlying black poly finish).

Carnauba wax can be used on glossy lacquered or varnished wood veneer finishes, but must not be used on satin finishes.

Unfortunately, One Grand products are not available in Singapore. I get my brother in the U.S. to send them to me. A can of Blitz Wax lasts forever if you make sure that it is always tightly capped so that the solvents don’t evaporate. You can get carnauba paste waxes in Singapore from brands like Meguiar’s and Zymol, but make sure that they are the WOWO kind (wipe on, wipe off). Avoid waxes that blend carnauba with other additives.

The Omega’s hygrometer

When you order a grand piano from Sauter you can ask for a hygrometer to be fitted inside the case as an optional extra. The picture below shows the natural hair hygrometer in my Omega.

Hygrometer in Sauter Omega

To the left of frame are the remote sensor units of two digital temperature/RH meters that I have. I use two to average out the readings. Their master control units are outside the piano to measure ambient room temperature and RH. What you can’t see are the RH levels showing on the meters. The digital meters are showing 58%, while the Sauter hygrometer is showing a tad above 48%. Inscribed along the top arc of the scale is a double-headed arrow indicating that a ‘normal’ RH reading should be between 40% and 70%.

The hygrometer’s case is set very snugly into a cavity in a block of wood attached to the rim. The vents that let air into the hygrometer are three large holes in the rear of the case, so that there is almost no mixing of the air in the hygrometer and cavity with the air around the wood block. Even when the RH of the room was at 70% for a couple of hours, the Sauter hygrometer crept up to around 50% over the same period of time. At first I thought that there was something wrong with the Sauter hygrometer. But when I popped it out of the cavity it eventually showed the same RH as the digital units.

What is the Sauter hygrometer measuring? I think that it is indirectly measuring the Equivalent Moisture Content (EMC) of the wood in the piano. From Guus van den Braak’s website in Australia I got the following:

• The ideal EMC for wood within a piano is determined by most manufacturers to be 8%.
• To maintain an 8% EMC, an RH of 42% is required. [That's where that magic 42% RH comes from.]
• The safest range of RH for wood is between 40% and 60%. [Sauter says 70%.] RH swings within this range reduce the risk of destruction of the cell structure. If RH swings are beyond this range, the cell structure of wood becomes fatigued and starts to break down.
• Wood that has too high an EMC is soft and structurally weak because the cells are full of water. The acoustic properties are dampened, swelling causes stresses where it is glued together (like at the rim or by the ribs) resulting in fractured glue joints and compression ridges commonly seen in soundboards (which will split when they dry out too much).
• Too low an EMC creates the possibility of a brittle cell structure. This may be stronger than a too high an EMC, but will result in splitting or cracking if pushed too far.

So, once again, what is the Sauter hygrometer measuring? If the EMC of the wood block in which the hygrometer sits is 8%, then the air in the hygrometer’s cavity should be stable around 42% because the moisture exchange between air and wood is in equilibrium. If the hygrometer is reading more (less) than 42% then the EMC is higher (lower) than 8%. As long as the RH reading is within the safe range then all is well. Now I understand why Ulrich Sauter told me that short term swings in RH are nothing to worry about as long as on average the RH in the room is within the safe limits.

This is an ingenious and accurate way of tracking the room’s RH and it’s direct effect on the piano. All that you need to do is to calibrate the Sauter hygrometer once a year.

Can high-end pianos survive the tropics?

Let’s take Fazioli as an example.

When I was making my final choice last year between a Fazioli F183 and a Sauter Omega 220, I investigated the warranty conditions for both manufacturers, and found the following on the Fazioli website:

The piano [is covered] for a period of 5 years starting from the date of delivery to the first buyer, determined by the receipt of the Sales Certificate. The Manufacturer herewith undertakes to fully remove – on a cost-free basis – all faults that may possibly occur in the above stated period of time as a consequence of manufacturing errors or defects.

Not covered by this warranty are all possible damages that may be ascribed to any of the following circumstances:

• Closeness to heat sources, in particular when the piano is being installed in rooms heated by under-floor heating.
• Closeness to windows.
• Exposure to draughts.
• Installation or use of the piano in climatically uncontrolled rooms. Ideal conditions are: relative air humidity within 45 and 65 percent; air temperature close to 20° (68° F).
• Transport and handling damages and their possible consequences.
• Careless use, abuse, undue tampering of any kind. Fazioli Pianoforti recommends that the piano be checked, tuned and adjusted at least twice a year by a qualified technician.

Clearly clause 4 was of concern. So I asked the dealer to ask if there was any variation of the warranty for pianos in the tropics. The answer from Mr Fazioli was yes, the 5-year warranty will be honoured provided that the following conditions are met:

• A Dampp-Chaser is installed (new condition);
• The environment’s temperature is higher than 30ºC, and the RH is no higher than 75% (replaces clause 4 of the standard warranty).

This was a pleasant surprise to me. I thought that pianos this expensive would have to be molly coddled. Not so! Even the Dampp-Chaser is no big deal because the only parts of it that will ever turn on are the heater bars, under the control of a humidistat.

Pianos and relative humidity in the tropics

The general received wisdom about the relative humidity (RH) level for pianos is that it should be held at a constant 42%, at a temperature that does not cause condensation of moisture on any surface in the room. However, that’s very difficult to achieve in the typical home unless you have museum-quality central air-conditioning. Much has been made about the horrible things that might happen to your piano if you deviate from this magical number and/or allow large swings of RH in the micro-climate around your piano.

Actually, pianos are really very hardy and resilient things, especially the expensive high-end ones! Even the large Chinese OEM piano manufacturers are learning what it takes to help a piano be less susceptible to absolute RH levels and RH variation. I spoke at some length with Ulrich Sauter about RH control, and his basic message is to just use your common sense. There is no need to panic nor be overly anxious. Some short-term variation is perfectly fine, even the large ones that I experience in my home. It’s not as if your piano will fall to pieces or seize up unless its really abused.

There are actually three aspects to this, as far as I can see.

The first is the control of RH on a long-term basis, where the micro-climate around the piano should vary as little as possible, on average, over weeks/months.

The second is the fact that there will be short-term RH variation on a daily basis. In my case, for example, if I have friends over and the air-con is on for a few hours, the RH can drop down to the low 40’s. But once the aircon has been turned off the RH slowly creeps back up to between 65 to 70% over the course of a few hours. In any case, Sauter (and I guess most other manufacturers of ‘tropicalised’ pianos) use a varnish on their soundboards that dramatically slows down moisture absorption. So short-term RH variation is typically not an issue.

The RH in the living room sometimes spikes up into the high 70’s, for example when I open the patio doors to go do some work on the potted plants, or if the exhaust fans in the kitchen have been on for a while and outside air is being slowly drawn through the small gap under the front door. But getting it back down to the 65-70% range is simply a matter of turning on the air-con for about 30 minutes or so.

These short-term variations are unavoidable unless you can run your air-con practically 24×7. The tuning will also drift a little, so it will have to be tweaked (which is why I tune my own piano). But once the piano has acclimatised you will find that the tuning will drift less. By the way, in the tropics, using a dehumidifier rather than air-conditioning is not a good idea unless you think that your home is not sufficiently warm and stuffy!

The third aspect is the need for air circulation within and around the piano, to prevent pockets of dampness from forming for extended periods of time. If you play your piano regularly then there is usually no problem. But if your piano is closed for a lot of the time, then having a heater bar turn on and off under the control of a humidistat is probably a good idea because it induces some circulation around the action (and to an extent the keys). You will also need air circulation around a piano, particular if it is backed up close to a wall.

And yes Sauter prefers control of the room’s micro-climate rather than in-piano heaters or humidifiers. Others have heard the same from Grotrian-Stienweg, Steingraeber, etc.

There are a couple of absolute no-no’s:

• Never ever locate the piano where direct or strong indirect sunlight falls on it. This is simply asking for trouble.
• Never ever let the RH stay at or above 75% for extended periods of time. An average of around the mid- to high-60’s is good. This means that you almost always have to close off the room from the outside for most of the time, and use air-conditioning for some of the time.