I have searched the MITRA forum and resources, and while I have read similar questions to mine, I am not locating an answer to my exact inquiry.
I am about to resume work on a large format oil on linen diptych after I had to set them aside for a few years. I recently received funding to complete the full project for an upcoming solo exhibition, so I look forward to completing these initial works. I want to use the soundest methods possible to finish these canvases, and would like to know if my approach sounds like the best route to take.
I am using oil paints made with walnut oil, and initially used a solvent-based alkyd medium cut 50/50 with OMS for my underpainting, then a walnut/alkyd medium with increasingly less OMS for subsequent fatter layers. I never adulterate more than 20% as I alter the fat-to-lean ratio. On large parts of each canvas, the underpainting and canvas tooth are still visible, while other areas are comprised of a second or third layer as I had developed them to near completion.
Here is my suggested approach to complete the works, along with my questions about each potential step:
1. Cleaning – I plan to give both of the canvases a gentle rub with OMS to get rid of any potential dirt or fingerprints, etc, before resuming painting.
2. Sanding? –
(a) do I need to gently abrade the areas where I got as far as a second or third layer to break the seal of the paint and insure best adhesion? Or only sand where any fatter third layers look glossy? I presume that I wouldn't need to sand the underpainting areas that still feature good canvas tooth.
(b) If sanding is recommended, since I don't want to alter my composition (so pentimenti isn't a concern), would I only need to break/scuff the surface, rather than sanding down to the underpainting? Would wet sanding with a little OMS or distilled water be advised for safety? (I know to wear an appropriate mask and dispose of the pigment dust responsibly, etc.)
(c) I also wondered if I'd only need to sand where the final highlight and darkest shadow layers are going, but that sounds potentially more complicated or confusing and would limit my method of execution.
3. Limiting layers – for best adhesion, in this case should I limit myself to a certain number of paint layers wherever possible? I typically use an indirect painting method to create a fairly naturalistic end result by employing glazes on top of a wet-in-wet or wet-on-dry base. As I recall, limiting yourself to three layers including the underpainting when possible is a good practice for longevity anyway…? The number of layers I would need to employ would also be affected by how much (if any) sanding you would recommend, because I will essentially have to redo anything I sand.
I welcome your input on the best way to proceed. While I know that resuming work on canvases whose layers are this closed off isn't necessarily the best case scenario, starting over does not appeal to me from the standpoints of both time and expense. I frequently see Old Master examples wherein the artist spent years completing the works or resumed painting after a few years, so I suppose there are worse studio practices.
Thank you so much for your time and expertise!