The proposed stages of treatment for Castiglione's Immaculate Conception are as follows:
- Conservation always begins with a thorough examination by a paintings conservator, followed by written reports that document the painting's present condition and make proposals for treatment. Photographs are taken before, during, and after treatment, to visually document the painting's condition and the progress of the project.
- Treatment begins with the removal of dirt, grime, and other accretions from the varnish layer by means of aqueous solutions. Then the discolored synthetic resin varnish is reduced with chemicals that will not harm the original paint layers. Finally, the distracting, discolored retouching in oil and synthetic resins from previous restorations is reduced or removed.
- The next step is to replace the deteriorated lining fabric on the reverse of the painting. But first, the newly cleaned original paint layer must be protected. A temporary facing of tissue is attached directly to the paint layer with an adhesive that can be easily removed later on.
- The painting is removed from the wooden stretcher. The old lining fabric on the back is then removed. Next, the old glue-paste adhesive on the reverse of the original canvas is reduced to prepare the canvas for its new lining. Any repairs to the canvas are made at this stage.
- A new lining fabric is prepared and affixed to the original canvas with a non-penetrating, stable synthetic resin adhesive. The adhesive is activated with heated platens expressly designed for use on large paintings.
- The lined painting is reattached to the wooden stretcher, and proper tension is placed on the canvas to prevent sagging and bulges.
- Attention now returns to the cosmetic problems. The temporary facing tissue and adhesive are removed from the paint layer, and a non-yellowing, stable synthetic resin varnish is applied.
- Losses in the paint and ground layers are filled and textured to match the surrounding original paint layers. Losses are inpainted with a stable, non-yellowing, non-discoloring synthetic medium.
- A protective backing board is secured to the reverse of the stretcher to keep out dirt and debris, prevent impact damage, and enhance the stretcher's structural stability. The painting is now ready to be reframed and hung in the museum's gallery. As the final step, the conservator writes a report detailing all aspects of the treatment.