I need to determine quickly and on site whether there is excessive
moisture in a variety of building products. Looked at Humidity
inidcator cards and coloured silica gels but I'm looking for an easy 
spray /brush on application that will confirm free water in porous
materials instantly and visibly (ie colour change must be easily
procurred - pref not too toxic)and if it inidcates proportionality
depending on amount of free water -better still.OH question what
workes well ?