Figure 4From: Assessment of desiccants and their instructions for use in rapid diagnostic testsDifferent types of silica gel. Upper left: non-indicating silica gel, transparent or opaque beads. Upper right: self-indicating silica gel, methyl violet as the humidity (colour) indicator. Lower left: self-indicating silica gel, cobalt dichloride. Lower right: partial-indicating silica gel: a majority of non-indicating beads with a few indicator beads.Back to article page