Originally Posted by martcol
Essentially, she allowed the full border of the negative to be printed, without cropping or masking, by filing out the negative carrying tray in the enlarger head. This resulted in the black borders. Later she used strips of card to produce a softer edge.
Negatives cannot be exposed to the edge of the film in the camera. This leaves a clear border around the image which would print black if it were allowed to show in the print. This unexposed edge is usually masked off in the enlarger in the negative carrier. You can also crop the image on the printing easel, which holds the paper. What this is saying is that she enlarged the negative carrier aperature to allow the entire negative to be printed -- clear border and all -- and printed the entire negative uncropped. You can achieve a similar result in Photoshop by increasing the size of the image canvas and filling the new area with black.
The use of card strips is a little more complicated as the effect you get will depend on the thickness and translucence of the card stock, how you made the strips (torn edges, clean cut, etc.), and how you placed the strips on the film. The strips were laid over the edges of the film in the enlarger and the print was made. The strips could overlay just the clear film border or it could encroach on the image. Depending on the paper type and thickness, defects and paper grain could possibly show. You could get anything from white to dark gray in the edge.
It's been a long time since I've seen her prints and don't remember what the edges looked like, so I can't offer an opinion as to how she made and used the strips.
In Photoshop, you would increase the size of the canvas to accomodate the new border. Where you go from there depends on whether you buy premade edge masks, an edge mask plug-in, or make your own masks. The basic idea is to fill the new area with the grayscale shade you are after and apply a layer mask to define the edges and grunge that you see in the border. You can get fancy and make compound borders as well for even more effects.
If you do a Google search on photo edges you will find many examples and tutorials and even some free grayscale masks you can download.