... we see colors not in their original state but as time has made them. This work of time—whether due to the chemical evolution of the colorant materials or to the actions of humans, who over the course of the centuries paint and repaint, modify, clean, varnish, or remove this or that layer of color set down by preceding generations—is in itself a historical document. That is why I am always suspicious of laboratories, now with very elaborate technical means and sometimes very flashy advertising, that offer to "restore" colors, or worse to return them to their original state. Inherent here is a scientific positivism that seems to me at once vain, dangerous, and at odds with the task of the historian. The work of time is an integral part of our research. Why renounce it, erase it, destroy it? The historical reality is not only what it was in its original state, but also what time has made of it. Let us not forget that and let us not restore rashly.
Black—The History Of A Color, Michel Pastoureau 2008, (my emphasis below).
The work of time is an integral part of our research. Why renounce it, erase it, destroy it? The historical reality is not only what it was in its original state, but also what time has made of it.
I think the 'restoration' of paintings is not that at all; it is simply the repainting, or more exactly, the over-painting by another person at a later date. I prefer seeing "the work of time" or the decrepitude of aging that adds a realness to the painting.