Quote:
Originally Posted by BOOSE
I ... discovered on reading reviews that a lot of people found that the hydrometer didn't change when putting these things in the guitar with the hydrometer in a case.
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I've been trying further to think how this could possibly happen (because on the face of it, it doesn't make sense), and I think I have an answer.
Suppose you have a 'wet' guitar. You put it in its case (which is also 'wet') with a couple of 10g silica gel packs and wait. Based on my own experience, I'd expect that after a couple of days the packs will have absorbed almost all the water they're capable of holding: 5 or 6 grams, perhaps. So they won't absorb significantly more water after that, and even if the relative humidity dropped a bit during those two days, it won't fall any further. If you don't have any idea of how much water has to be shifted, you may conclude that the system isn't working.
But the point is, those few grams of water are peanuts compared to the total amount of water that has to be removed (from the guitar AND the case) before the in-case humidity gets down to the ballpark 45-50%. If you don't change the gel packs frequently, you may think nothing has happened, because the packs will become saturated very quickly. I think that's the likely explanation of the reports you've read.
Of course once the RH has fallen below 50% and has become stable, things get much easier to cope with (as I've described above). But for the first few weeks, starting with a 'wet' guitar and case, the gel packs have to be changed very frequently, because we have to get rid of
at least 40 or 50 grams of water overall, to achieve the goal.