In this paper, we develop the notion of design archives to understand how different forms of knowledge are systematically accumulated and shared in and across design processes. Drawing on philosophy and media theory, we present a working definition of design archives as more than documentation. Through an interview study, we investigate how various archives systematically inform design work and govern the way design processes are represented and reflected upon. The study provides insights into an abundance of tools used to access, record, store and share information. We highlight the difference between personal, shared, and public archives, different archival barriers for sharing, how prototypes act as (an)archival conduits of design potentials, and how information (and people) tend to get lost in the archives. Finally, we discuss how a design archival approach might help identify power relations in design while also facilitating a move from 'dead' to 'living' archives in design work.