Regarding Scott Devine's query about cards with a "secret message" written in potassium nitrate, the amount of potassium nitrate involved would be so small that it is most unlikely to be a hazard. Normal storage conditions should be perfectly adequate.
Barry Knight St Albans England ****** Unsubscribe by sending a message to [email protected] Archives through August 2016 at http://cool.conservation-us.org/byform/mailing-lists/cdl/ Archives from September 2016 onward at https://www.mail-archive.com/[email protected]/
