Recently we had some replastering done in an 1880's house on the grounds of the Dayton VA Medical Center. Between the second floor ceiling lathes and the third-floor floor we found chunks of coal (clinkers), and now we are wondering whether or not clinkers were ever used as insulation. If anyone has any ideas about this, please contact Melissa Smith at: [log in to unmask] Thankyou in advance for your help!