Humidity Research and Questions

Since receiving my Noj set and learning about the risks of humidity, I have researched it as extensively as I could, however, the information available on the internet is relatively sparse/vague, so I’m sharing what I have found, and asking a few questions for any humidity experts out there:

Research:

1. Relative Humidity (RH): The amount of water vapor in the air (moisture in the air); important for chess products (and wood products in general) because wood is hygroscopic, meaning it exchanges moisture with the air around it (absorbs/releases). Low RH can result in cracking (because the wood becomes dry), high RH can result in excessive swelling (because the wood becomes saturated), RH swings can result in warping (because the wood shrinks/expands with different moisture content). Generally, winter is low RH, summer is high RH; regional climate makes a difference (proximity to bodies of water, foliage, etc.). Different types of wood are more or less resilient to RH; ebony is very susceptible to cracking, rosewood/walnut are softer woods, boxwood is solid, maple is very durable. Freshly cut wood (“green” wood) still has a lot of “life” in it which causes it to expand/contract a lot, which is obviously not desirable for wood working; experienced wood workers use aged wood that has been “stabilized” as much as possible (e.g., 10-50 year old wood for fine instruments), so that it does not “move” very much after it has been crafted into an object, which limits (but does not eliminate) RH issues.

2. Recommended RH: HoS recommends 35-45% RH/65-70 degrees F in winter, 55-65% RH/70-75 degrees F in summer; I see no reason why season would *command* a different recommended RH in a controlled environment (like a house), so we can conclude from this that 35-65% RH/65-75 degrees F is the “safe zone”. My hygrometer (more on this below) says 30-50% RH is optimal; it says 29% or less is dry, 51% or more is wet. Based upon all of this, I think 40% - 50% RH is an optimal target range, and 45% the optimal target level.

3. Observations About Other Products: Fine wood instruments and cigars are even more sensitive to RH than chess products, and there is a suite of solutions available on the market for owners of these products (humidors, instrument case humidifiers, humidity control packets, etc.). I read that, at 45% RH, a guitar performs optimally; at 35% RH, performance begins to suffer from dryness; at 25%, extreme performance impact; at 15% cracking; from this we can conclude that 34% RH or less is the “dry zone”, and 25% or less is the extreme risk zone (which seems to align with research point #2). RH control products for instruments don’t really translate to chess products; cigar products seem to carry over nicely (humidors are very similar to chess coffers).

4. RH Control Solutions:

--Hygrometer: A tool used to measure RH and temperature; this is a must. I found a GREAT one on amazon (after quite a bit of research), for $20 CAD; it works great: https://www.amazon.ca/AcuRite-01083M-Accuracy-Temperature-Humidity/dp/B01HDW58GS/ref=sr_1_2?s=kitchen&rps=1&ie=UTF8&qid=1548955296&sr=1-2&keywords=acurite+hygrometer&refinements=p_85%3A5690392011. You will not find a better hygrometer anywhere near this price point; extremely accurate, universally good reviews, easy use (no calibration required; just insert two AA batteries).
--Humidifer and/or Dehumidifier: Tools used to add/remove moisture from the air (humidifier adds, dehumidifier removes); requirement depends on your climate (dry areas require a humidifier, wet areas require a dehumidifier). I found a number of great room humidifiers for low prices; dehumidifiers are expensive. You can add a humidification unit to your HVAC system, however, this is expensive/unnecessary/not as effective as a room humidifier (all you really care about is the room your chess products are stored in; whole-house humidification is not reliable because duct-work, windows, etc. can impact moisture distribution in a house, and the humidification unit’s RH reader is probably only looking at one area of the house, etc.).
--Humidity Exchange Products: Disposable products that exchange RH with the environment to keep RH within a certain range (only in a small area, like a coffer). I don’t like disposable products and I don’t trust a packet of salt/gel or whatever in a coffer with my chessmen, however, this is a decent solution if you’re ok with that. The issue, however, is that your chessmen will only be safe inside your coffer; assuming you actually play chess from time to time, the RH of your playing environment will also need to be controlled, so I would only use a humidity exchange product in addition to a humidifier solution.
--Home Solutions: I have found these to be ineffective (pots of hot water, etc.); a hot shower to create steam near an area is the only thing I found to be effective, however, this effect is short-term, and obviously impractical.
--My Solution: I went with the hygrometer/room humidifier combo; my region is somewhat dry year round, however, my home is usually within the target RH range, except for the coldest months where it dips below 25-30%. I purchased the hygrometer I mentioned above ($20 CAD) and a room humidifier ($60 CAD); not a huge amount of money to protect my investment.

Questions (to satisfy my OCD):

5. High-quality chess products should be made of properly prepared wood (dried, cured, etc.) and should be covered with several layers of finish-coat (waxes, stains, etc.); the wood of a fine chessman, for example, is “sealed” with several layers these finish-coats, so I’m not sure how it still exchanges moisture with the air, but I suppose it must be the case, because fine ebony chessmen crack; can someone confirm/comment on this?

6. RH swings are unavoidable; when does warping become a concern? Specifically, what percentage of change and in what time period? For example, I would imagine a 50% upswing in RH in 10-15 minutes would cause some issues. I believe the rate at which finished wood products exchange moisture with their environment is quite slow, which explains how they can “survive” regular use, but I’m not sure on this.

7. What is meant by “warping”; what kind of severity are we talking about? Board warping is fairly common and easy to detect (the board will be curved and/or not perfectly flat), however, warping is less obvious with chessmen. Irregular shrinking/expanding concerns me, because this means the shape of the product is changing, but I’m not sure on what scale this is occurring (are we talking about microscopic “warping”, or is the face of my beautifully crafted knight going to change!).

8. Coffer storage seems to be a good idea, because it reduces air exchange with environment, meaning reduced number/severity of RH swings; would chessmen in a coffer retain the moisture they have indefinitely, or do they need additional moisture as time goes on (i.e., do you need to give your chessmen a drink of water from time to time)? I would imagine that, because the wood in a finished wood product is not really alive anymore, it would retain the level of moisture it has indefinitely, when kept in a sealed environment.

9. I have read that boards should be stored vertically, to allow air moisture to contact both sides of the board (chesshouse recommends this; they actually sell a product called the “chess shelf”, which is quite hilarious); thoughts? I assume for this same reason, that a board bag or other board storage option is probably a bad idea.

Regarding your comments in item #8:

Wood does not retain water "indefinitely", unless it is alive.  "Dead' wood (after a tree has been cut down, the wood becomes "dead" as it is no longer part of a living tree, which draws its water content from the ground).  Once the tree is cut down, the wood begins to lose most of its retained water due to evaporation.  But even so-called dead wood can absorb (adsorb?) water via the moisture content (humidity) of the air it is exposed to.  This can be seen, for example, in the fact that guitar bodies swell and contract with variations in humidity exposure.  

The principles explained in the following article by Taylor Guitars on humidity control for guitars, would apply as well for chess pieces, boards etc...

https://www.taylorguitars.com/support/maintenance/symptoms-dry-guitar

http://www.differencebetween.net/science/difference-between-adsorb-and-absorb/

Also your item #9:  As long as the pieces or boards are not stored inside something which completely prevents/blocks moisture from the air from reaching the wood (for example, an air-tight plastic bag), the moisture from the air can and will ultimately get to the wood, albeit somewhat more slowly depending on the effectiveness of the storage compartment in blocking outside air.  So for example, when storing boards in cloth bags, or pieces in wood coffers, the air, with its attendant water content, will eventually get to the wood, and do its thing. 

Consider the following article about using guitar humidifiers:

https://www.taylorguitars.com/support/maintenance/using-guitar-humidifier

Careful reading will reveal that even though the guitar is stored inside a case (along with the humidifier), eventually the humidifier needs to be replaced, because it has dried out (i.e., its water content has evaporated).  But where did the water go?  It is not retained indefinitely (only temporarily) inside the guitar case, otherwise there would be no need to replace the humidifier or recharge it with water.  The water eventually evaporates into the outside air (assuming the humidity/water content of the outside air is lower than inside the guitar case).  The case only slows down this evaporation process, it does not prevent it, over the long run.

I suspect you are over-thinking this.  Wood absorbs moisture from the air quite slowly and moisture moves through timber quite slowly.  Finishes are more or less permeable (some very, some hardly at all, but even something like shellac is used to reduce moisture take up) and slow down the moisture change even more.  Rapid changes in humidity don't have much impact at all, its prolonged exposure that has some effect.  How much effect depends on the temperature and humidity gradient.  Warping is the result of dimensional change (shrinkage with drying for example) and release of tension in the wood (trees aren't perfectly relaxed as they grow) but at small scales these effects are usually small.  The linked PDF includes information about drying, dimensional change etc, its not talking about finished wood, but the percentage movement for example and impact of humidity will give you an idea of the numbers.   You should consider what your local humidity is like and try to let the pieces adjust to that.  If you live at the equator with say year round 80% humidity then you may have a problem, living far inland in a hot climate things will dry out pretty severely, but most of us live somewhere more comfortable between those extremes.   Where I live the mean humidity varies between 55% and about 70% over the year, which is pretty close the the range you are looking at and I live somewhere fairly humid.  

https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0003/390288/Seasoning-of-Timber.pdf 

I’ve owned a wooden Lardy chess set for over 50 years and wooden walnut and maple board for almost that long and neither seemed to have been affected by changes in humidity over that time period. I’ve lived in various locations and homes including some without air conditioning.

The pieces were stored in a wooden box that is not air tight. I usually stored the board on its side since that was the most space efficient way to do it. The board was straight when I sold it.

I’m just passing this on as one data point. What I don’t know is how well wooden chess products are typically made today in comparison to how well similar products were made back in the 1960s. I have a few modern wooden sets but have not owned them long enough to assess how well they might hold up over time.