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Wood Drying - Part Six

The weather and our guitars. What are the implications?

In this part, we shall examine the correlationships between temperature and humidity. Ultimately we wish to ascertain the impact of their relationships on our guitars.

 

Weather of Singapore, 75 years

 

Most Singaporean will describe the local climate as wet and humid in general. However, we are not conscious of the figures that are relevant to the well being of our guitars. A quick check at the National Environment Agency’s (NEA) website (http://app2.nea.gov.sg/weather_statistics.aspx), one can obtain weather statistics of 75 years.

 

In the case of guitars, we are concerned with temperature and relative humidity (RH). After filtering the unwanted data, the table below should be relevant in predicting local guitars’ conditions in relation to Wood Moisture Content (WMC) or Equilibrium Moisture Content (EMC).

 

For every measure of temperature, we can obtain its corresponding RH level too. With both temperature and RH measurements, the EMC of any given woods that reside within the same environment can be calculated. I found a website that allowed user to input temperature and RH data to obtain the EMC level. The link is: http://www.csgnetwork.com/emctablecalc.html.

 

Table 3.0

 
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My Two Cents


I shall attempt to share my perspectives below,

 

Temperature fluctuations - I reckon this property has the least influence on the EMC of wood in Singapore. While temperature was easily felt, it has much less effects on woods' EMC than we accord it for. E.g. referring to the table above, data from NEA’s website, for December max/min temperatures are 33.8/20.6°C, gap of 13.2ºC and the 24hr mean RH is 86.9%. The converted EMC range is 18.1/18.8%, gap of 0.7%. Despite the big temperature gap, the conversion did not produce EMC range of proportion nature. This may suggest that the relationship between temp/RH and EMC was not linear and suspiciously not directly proportional too. The EMC difference was merely 0.7%. It can be seen that temperature has little influence on the EMC level.

 

Relative Humidity - In working out the EMC from the temperature and RH data, it was cleared that RH ranges have greater influences in the resulting EMC compared temperature fluctuations. As long as the RH was at high levels, the corresponding EMC levels remain high regardless of temperature changes. This claim is supported by the table 3.0; to illustrate the RH effect, let’s consider data No 2, 3 and 6 of table 4.

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What do they mean?


From data No 2 & 3, temperature range if 31.7ºC - 19.4ºC = 12.3ºC. The corresponding RH range is only 1 to 2.4%. We can infer that despite the pronounced temperature differences, given the RH range is narrow. The narrow changes in EMC further validate the proposition.

 

As for data No 6, the RH remained constant as temperature fluctuates. For RH of 61.3% and temperature range of 35.0/19.7°C, gap of 15.3ºC, the resulting EMC was 10.7/11.3%, gap of 0.6%. No matter I approach from temperature ranges or RH ranges perspectives, the trend was that influences from RH were much greater than from temperature.

 

So what has it got to do with our guitars?

 

Here is what I think,

 

We are aware that temperature can be reduced drastically when we’re under shelters. Even under trees’ shade, you can knock off up to 5°C easily. Logically, in avoiding soaring temperature, we store our guitars indoors, away from the direct heat of the sun. So our guitars are safe? Yes, probably only from the soaring heat but not from humidity.In the early sections, RH was observed as the key driver of EMC. I have also stressed that the impact of temperature has little effects on the resulting EMC levels within woods, which include our guitars. Many people erroneously assumed that in low temperature environments, the corresponding RH would be low as well. Even under sheltered conditions, effects of high humidity persist. The effects were pervasive and hard to prevent. Two sets of conditions as example (pictures on left).

 

Outdoor conditions - Temp (35°C or 97°F) , RH (76%) and EMC (14%)

 

Indoor conditions - Temp (28°C or 82°F) , RH (73%) and EMC (13.6%)

 

The indoor temperature is naturally lower than outdoor by a big margin but RH doesn’t exhibit similar trend. The temperature differences only account for a 0.4% discrepancy in the two EMCs. The effects from high humidity on our guitars are not to be underestimated. As EMC increases beyond a certain level, guitars will begin to exhibit physical changes, a.k.a. distortion. Especially for acoustic guitars.

 

The context was Singapore’s climate and guitars. Therefore I have used the data from NEA’s website and the converter to work out the 12 months average EMCs in table below.

 

The EMC levels were generally higher than 16%. In the classifications of WMC levels, 16 to 20% suggest possibility of elevated moisture level in woods. Therefore, it can be concluded that guitars in Singapore were exposed to RH levels that were adequate in increasing the WMC within guitars regardless the storage location to a level that warrants deliberate treatments to restore their WMC to recommended range with the exception of guitars stored within climate controlled environment.

 

In another words, guitars in Singapore have no chance to escape from the influences of RH. The same should apply in regions of similar climate patterns. Consequently to retain pristine condition over the guitars’ life span was a definitely a tall order. In short, the inevitable can’t be prevented. However we can administer ways to reduce the impact and maintain our guitars in good playability within this unforgiving environment.

 

Comparing the average dehumidified EMC of the old guitar of 14.9% (Table 2.0) to Singapore’s 24hrs EMC Mean of 17.34% (Table 5.0), the dehumidified old guitar did carry less moisture than expected, which is comforting to know that dehumidifying is the correct direction to go. However the recommended and discussed solutions available in the guitar community pertaining dehumidifying guitars were mostly improvisations. There was no dedicated solution(s) that work currently.

 

As for attaining factory WMC levels (8.5%) in Singapore may be possible but it wasn’t affordable to many. Accessibility is important to keep the guitar industry growing. Methods that require abundance of resources will not benefit the community except a few privileged individuals. As such any methods pertaining to guitar care should be catered for all.

 

Admittedly, more can be done to bring the old guitar’s moisture level lower but at what price? We may ask. Before we pursue further, it may be wise to spend time in playing our guitars. Resetting our guitars to suit your own style, if not send it a qualified person to do so. Perhaps, dehumidifying is essential but hitting the target of 8.5% may not be necessary.
 

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