Metal Plaque inside Museum Frame - THOUGHTS PLEASE!

[penninejohn]

Hi Everybody - Long term observer; first time contributor...
I've been lucky enough to be given a commission to frame a set of tapestries for a museum..
Now, the good people at the museum are not in a position to fork out for full 'museum quality' framing, but they do want something at the high end of conservation - sort of 'near-museum' quality if you will.
Now, the museum's board has agreed to the following approach:
Deep rebate oak moulding (lined with conservation quality rebate tape) glazed with Artglass AR99; below this a 9mm spacer (sealed) followed by museum window mount; tapestry below this (stretched over museum quality board) and Corri-cor archival water-resistant backing below that.
BUT there's just one thing that worries me - they want each framed tapestry to feature an engraved metal plaque INSIDE the frame... ie, below the glass; fixed to the bottom border of the window mount.... am concerned about conservation issues here; they ideally want solid brass plaques - am assuming that it will be absolutely essential to seal these with an appropriate lacquer to keep the metallic shine; but am concerned about any conservation issues that may arise from having the very presence of a brass plaque within the frame; and even the lacquer itself may be an issue. Any thoughts on this would be VERY welcome!
Am actually wondering if I steer them towards opting for engraved brushed aluminium plaques instead - as I am working on the idea (maybe wrongly!) that no lacquer would be needed, and that aluminium itself may well demonstrate superior conservation qualities.
Cheers, John

[Not your average framer]

Why is it absolutely essential to lacquer the brass plaues inside these frames? most lacquers are not necessarily things that will last forever and brass is not particularly guarenteed to remain it is same state for ever. Brass is an alloy of copper and zinc, that's why it is necesary to keep brass cleaned and polished. I think that making some enquiries about that arcival wax produced by Picreator might be a very good thing to do. It is quite permanent and protects metals from the presence of oxigen.

Also, maybe the plaque can then be encapsulated and mounted behind it's own window in the bottom margin of the mount. It might be a good idea to talk to someone like Mal Reynolds about this.

[penninejohn]

Thanks for this - and a really good point about the lacquer... am thinking that renaissance wax might be the way to go. Am still wondering about the choice of brass in the first place though; if it's inert enough to be permanently included inside a 'near-museum' quality framing job,- could it ultimately cause damage/discolouration elsewhere within the frame(?); I suspect that oxidation would not be a huge problem (apart from tarnishing the plaque itself) as oxides of both copper and zinc are basic (as in the opposite of acidic) so no problems leaching acids or similar - but the theory doesn't always match the practice and I would hate to mess this one up! That's why I'm thinking about the Aluminium alternative; which naturally forms its own very thin oxide layer that seals the surface preventing any progressive degradation... it's appearance should, in theory, never change (but see previous sentence about theories!) Wondering if anyone out there has ever done anything similar - and if it worked!?