| abstract |
A time indicator comprising a first reservoir ( 13 ), a migration medium ( 11 ) and activating means for bringing liquid from the first reservoir ( 13 ) in contact with the migration medium ( 11 ) so that after activation the liquid migrates through the migration medium ( 11 ) producing a colour change therein. The activating means comprises a second reservoir ( 16 ) connected between the first reservoir ( 13 ) and the migration medium ( 11 ) whereby after activation the liquid travels relatively rapidly from the first reservoir ( 13 ) to the second reservoir ( 16 ) and then migrates relatively slowly along the length of the migration medium ( 11 ) over time. |