The relative humidity inside a closed showcase containing a relative humidity buffering agent will always drift at least slightly, because the case cannot be made perfectly airtight. For the closed showcase, the greatest cause for the drift is the difference in pressure inside and outside, which is reversed repeatedly. A flaccid airbag connected to the inner space is thought to be effective in preventing pressure changes, and stabilizing relative humidity for long periods. Experimental work continues but preliminary results verify the effectiveness of the bag for specially designed painting cases. -- AATA