Low RH in case with activated charcoal and silica gel
Liz Did you check the rh of the activated carbon? How much carbon is there? How large is the showcase? What else is in the showcase? How long did it take for the rh to change? Was it ever satisfactory? Do you have a graph tracking rh / time? It seems entirely plausible that the carbon was shipped in a dry (or very dry) state, and that it has ample capacity to absorb lots of moisture from the showcase (including the preconditioned silica gel). Answering some of my initial questions might provide clues. I also have questions about how you tested your silica gel. Also note that to test silica gel, best results will be found by sealing your sample of sg and your rh probe in an impermeable bag or small box, and then be certain to give the hygrometer/silica gel/air combination time (hours to days) to "settle". This is important as it is very possible that the rh of the exterior of the sg grains differs from the interior, and it may take some time to equalize. A further comment: For your application, sg is not the best product - it is superior when creating or buffering dry conditions (under 40%). A sg-based buffering compound like Prosorb has far more capacity in the middle range (rh 40% to 60 %). js -- Jerry Shiner Keepsafe Microclimate Systems www.keepsafe.ca +1 416 703 4696 [email protected] Skype: jerry.shiner Specializing in the design, procurement, and installation of environmental control systems for museum and archives ****** Unsubscribe by sending a message to [email protected] Searchable archives: http://cool.conservation-us.org/byform/mailing-lists/cdl/
