Historical clue formulations

• Seep through — 2017-09-03
• Slip through, say — 2014-07-19
• Diffuse slowly — 2009-04-12
• Cause to be absorbed — 2003-02-15
• Diffuse — 1998-05-03
• Filtrate — 1997-04-11
• Absorb gradually — 1994-07-31