Well, this isn't gonna set well with all the preservation addicts on the forum but, nonetheless, this was a pair of Redlin plates that I designed a framing for about 14 or 15 years ago. The 2 frames were pinned together with short lengths of black walnut dowels, the same wood as the solid black walnut frames, and dowels were broken on the last move I made. I had to tear the framing apart to bore out the broken stubs and replace the dowels and I decided to check the mounting of the plates since I had the packages apart. They were intact and fine. I cut one of the plates from its mounting and completely cleaned it of all mounting materials in a matter of maybe 7 or 8 minutes!! I re-applied the mounting material and re-assembled all the parts after cleaning and replacing the glass with 2 pieces of Museum glass.
The mounting medium??, clear silicone adhesive. I used clear silicone adhesive on the recommendation of the American Institute of Conservation back in the early 90's and it lasted longer than the pins holding the 2 plate frames together. I left the other plate mounted with the original silicone adhesive. Maybe I'll tear that one down in another 10 years or so and see if that adhesive is still pliable and doing its job.
I did probably 400 or more collector plates similar to this when it was the rage to buy and display them back in the 90's and I have not had a single plate come back for the adhesive failing.
You use your own judgement on using or not using silicone but it is completely removeable with absolutely no harm done to the glaze of the plate, it may have some minor outgassing if you don't let it dry for at least a few days before sealing up the frame package but I understand that now there is an archival grade of silicone, and it stays pliable for many years.
Using silicone to mount the plates allows the framer to mount the plate back off of the surface of the glass which could cause more damage than the silicone would cause. One of the major reasons why it isn't a good thing to "sandwich" a plate behind a sheet of glass it that the normal vibrations in most walls will wear the 24k. gold plating off the edges of most collector plates and that causes visible damage to the plate and lowers whatever value the plate may have to the owner. I know this to be true as I have had plates brought in to my shop that were placed in the same type of frame once sold by Wild Wings in their catalog and the plating was visible on the backside of the glass when I tore the package apart to reframe the plates.
Here is an old photo of the set of Redlin plate to which I referred earlier.
, mounted to a felt covered masonite board. The board has a hole in the center to allow the customer to view the plate ltd. edition info. They are ok.... with using mighty mounts to attach, but would prefer for the replacement mounting be invisible.
