Summaries are presented of the history and manufacturing techniques of tracing paper, tracing linen, blueprints (or cyanotypes), diazotypes; the inherent causes of deterioration and problems associated with treatment which tend to make traditional conservation techniques difficult or impossible are analyzed. The modern alternatives which present most hope for the future are photocopying onto archival quality paper or onto polyester film and silver gelatin photography onto polyester film or print papers. Further research is needed to assess the effects of traditional conservation measures on duplicate materials.