I dry mount my pictures onto a 100% acid free rag mat board (4-ply I think). I wonder, does this the job as a backing board as well when I frame it or should I use a foamboard as well as a backing board?
when I have an acid free mount board (and a dry mount tissue as well) between the photo and the backboard, does the back board need to be archival/100%acid free?
when I have an acid free mount board (and a dry mount tissue as well) between the photo and the backboard, does the back board need to be archival/100%acid free?
Yes. Remember that all materials will be 'trapped' behind glass. The dry-mount tissue will act as a seal, but the print still has a large and vulnerable image surface. Some framers even add a barrier sheet between the mount and the backboard to protect from environmental gases.