At Memento, we've always done custom picture framing to conservation standards. Sometimes we even go all the way - to fully archival treatment - when the artwork/object warrants it or a client desires it. Ten or fifteen years ago, conservation framing became the hot trend in our industry and now everyone supposedly does it.
True conservation standards require 100% cotton rag (museum) matboard, similarly acid-free backing materials and no glues, acidic or corrosive materials used in any aspect of the framing. Artwork is supported on the backing via linen hinges or archival corners, thus nothing is ever glued down.
As far as glazing is concerned, here in Earthquakeland we prefer acrylic to glass to prevent breakage and damage to the art, photograph, etc. within. We may also suggest UV plexiglass for its light protective properties or even UV/anti-reflective museum acrylic. However, acrylic acts as a magnet for graphite, chalk or pastel works on paper, so we use glass in those instances or the art may transfer from the paper to the inside of the acrylic. We once had a client bring in her grandmother's pastel portrait which had been framed with acrylic, shipped cross-country to her and during its trip the portrait was completely "sucked" off the paper it was on.Luckily, we were able to recommend our paper conservators to her and several months and much money later, grandma was back where she belonged!
We also use spacers or create a shadowbox.to create breathing room between the art and its glazing.
This is all pretty dry and boring information that designers and clients shouldn't have to bother with. You should be able to confidently entrust your artwork, photographs & mementos to a framer you can rely on to protect them and your investment in them. So, as a test, walk through your home & look at the beveled edges on all of your mats...if that slanted edge looks beige/yellow/brown instead of white-ish, you have acid in old mats which is doing all kinds of nasty things to whatever's within...Have the mats changed ASAP!