meanstreak Posted February 1, 2011 Share Posted February 1, 2011 lol I live just south of Houston and rarely does the indoor humidy get below 70% even in the dead of winter with the heat cranking or the middle of summer with the A/C on full blast! I think my guitars need a de-humidifier! Link to comment Share on other sites More sharing options...
brians356 Posted February 1, 2011 Share Posted February 1, 2011 Beware getting fixated on the typical factory standard of 47% RH. What's missing from that is the temperature that went along with it, typically 70 f or close to that. What is important is the moisture content held in the air mass. If you turn down the thermostat and let your house cool way down (in a cold region) to, say, 58 degrees, your RH dial may read 47% and you figure "Cool, that's ideal!" Now, if that same air mass is then heated back up to 70, the RH will magically drop down to well below 40%, which is too dry. But in the closed system, the moisture content stayed the same. The RH figure by itself is kind of worthless. Unfortunately, Taylor Guitar's essay on humidity only says their factory is at 47% RH, but doesn't say at what temperature. We need to know that to duplicate those conditions. Brian Link to comment Share on other sites More sharing options...
57classic Posted February 2, 2011 Share Posted February 2, 2011 Beware getting fixated on the typical factory standard of 47% RH. What's missing from that is the temperature that went along with it, typically 70 f or close to that. What is important is the moisture content held in the air mass. If you turn down the thermostat and let your house cool way down (in a cold region) to, say, 58 degrees, your RH dial may read 47% and you figure "Cool, that's ideal!" Now, if that same air mass is then heated back up to 70, the RH will magically drop down to well below 40%, which is too dry. But in the closed system, the moisture content stayed the same. The RH figure by itself is kind of worthless. Unfortunately, Taylor Guitar's essay on humidity only says their factory is at 47% RH, but doesn't say at what temperature. We need to know that to duplicate those conditions. Brian I think their temp is in the neighborhood of 70 degrees. I believe I've read elsewhere that 47% is a target number other builders work with. Gibson states in their Acoustic owners' manual, "Store your Gibson at 40%-50% relative humidity and 70 degrees. Gibson built your guitar in these conditions. Avoid fluctuations over 20% of both temperature and relative humidity." They continue by telling of the adverse affects of not following this guideline. It is a guideline only, rigid adherence to 47% and 70 degrees is not expected or realistic. It is an ideal. Link to comment Share on other sites More sharing options...
brians356 Posted February 3, 2011 Share Posted February 3, 2011 Ok, so back to what I was saying, let's assume the "ideal" is 47% at 70 degrees. If you keep your room in wintertime at 64 degrees, and the RH is 40%, that may seem like it is within 20% of "ideal", but it's actually considerably lower than acceptable, because if you heated that room to 70 the RH would drop to something like 35% - too dry. On the other hand, suppose your room is 70 degrees and the RH reads 47% (or "ideal.") Now, turn down the thermostat and let the temperature fall to 62 degrees. The indicated RH will shoot up to something like 55 - 60%. Moral: If you keep your room well below 70 degrees, you need the RH to read well above 47% to be "ideal." Brian Link to comment Share on other sites More sharing options...
BigKahune Posted February 3, 2011 Share Posted February 3, 2011 ... If you keep your room well below 70 degrees, you need the RH to read well above 47% to be "ideal." ... Good point. Relative Humidity is the humidity relative to (as in 'relation to') the temperature. Relative humidity is the ratio of absolute humidity to the highest possible absolute humidity, which depends on the current air temperature. So RH 47% relative to 70°. Link to comment Share on other sites More sharing options...
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