In August 2017 I wrote an article titled ‘Humidity and your classical guitar’, and ever since then, I have been recording local humidity levels. In a previous article, I explained the system and mix I use for in-case humidity control. In this article, I want to give some feedback on the readings I have taken.
I did not record humidity levels every day, but only when there was a meaningful movement from the norm. I live in the Johannesburg area of South Africa and the general average humidity here is 60%. The average highs are 70% for 3 months of the year, and the average lows are 45% for another 3 months. However, from time to time the conditions change dramatically to averages of more than 70% or less than 25% for a week or so at a time.
During the last 2 years, I have recorded 241 humidity readings and these reveal the following:
61 readings were 65% or more of which the highest was 81%. 48 readings were 25% or less and the lowest of these was 10%. However, and this is an important ‘however’, the highest in-case reading was 62% and the lowest was 41%. So, although the average in-case humidity of my guitars was 51% compared to an external average of 47%, my instruments were protected from protracted levels of over 65% or under 25%. When the external humidity was 81%, the in-case humidity was 62%, a 19% difference. When the external level was 10%, the in-case level was 41%, a massive 31% difference.
Another major benefit of in-case humidity control has been that the levels the guitars have to deal with change very slowly compared to sudden and drastic external changes. A sudden drop to 10% can cause a hand-made guitar to crack and a sustained level of 80% plus can loosen the seams and frets, change the fret-board inclination, and make the instrument sound soggy and buzzy.
So, there you have it. Even in a moderate climate such as Johannesburg, in-case humidification is definitely needed.