How to frame silverpoint

​Hi there.  As long as you’re not creating an anoxic environment (very low or no oxygen) within the frame – for example, by using a specially-designed sealed package to create an anoxic microclimate – oxidation will still continue, even when a metalpoint is framed under glass.  Just framing a metalpoint normally may slow down the oxidation slightly, but will not stop it.  In terms of the oxidation process, the time it takes for patination to develop will depend upon the environment, including pollutants in the air.

As a side note, I would make sure to use spacers when framing so that there is space between the glass and the surface of the metalpoint drawing.

Since this is an antique medium, one can look at Cennini and similar authors to see what they say. I know that he warns against lead white out doors. All framed sheets of paper should have glazing sheet in front of them, since air pollution is both particulate and gaseous. Even if one wants the oxidizing gases to darken the silver, their effect on the paper and the effects of the particulates should be avoided. The silverpoint artist can enhance the oxidation by placing the drawing near a sulfur source, like wool, until it gets dark enough to satisfy the artist, knowing that even in an ordinary frame, the oxidation will continue, anyway. 
And yes, please, under glass, to protect the paper and keep aerosol oil, spores, pollen, and a panoply of other dangers. 
Hugh Phibbs –Exhibition, Housing, Display (Independent)

I sensing that the silverpoint drawing in question has been recently created and that the medium, in the artist’s opinion, has yet to achieve its final darker color.  If such a drawing is to be framed, the insertion of glass or acrylic sheet (the glazing) will not prevent continued oxidation, if the drawing is framed in a standard manner.  There is sufficient oxygen in the space between the drawing and the glazing to maintain the oxidation process.  As long as there are exposed silver alloy particles available for oxidation, the mechanism will occur.  
Air pollution speeds up oxidation so it’s possible that leaving silverpoint drawings unframed is preferable, however, this is a different issue entirely!

Margaret Holben Ellis