I always sandwich the glass/mount/backing.
It serves two purposes: Firstly it leaves you with a unified single unit that you know bits are not going to get into. I make the frame
after the sandwich is complete. I can have any number of sandwiches waiting for frames. Better than a load of loose elements.
Whats more, you can assemble everything face-up so you can see any bits and remove them. Once sandwiched you can rest assured
that it's frame-ready. When I started I did what a lot of framers did, that is to put the frame face-down - put the glass in and clean
it and then load the mounted work followed by the back. This seemed to intuitive way to work. A rep from Scharf Mouldings gave me
the idea when we were discussing how to seal aluminium frames.
Secondly it stops the little flies creeping in. FYI they
always go in from the front. The tape applied on the back is largely cosmetic.
Wriggling under the rebate lip they have two choices - go under and get stuck or go over and end up somewhere in the back where they
can do no harm. Why they do it is one of natures' mysteries, but they can be very destructive.
I use masking tape, which I know is not archival but it really doesn't have to be as it comes nowhere near the artwork. It will stay sticky
and last for years. In terms of holding the sandwich together it only has to last until you get it installed in the frame.
As they say in the good old US of A, "It's a no-brainer".
