Hello again Pit,
My comments stem from the image provided of your cleaned Skarnick and Fiszbein eagle in post #483. It’s entirely possible that this photograph doesn’t do justice to your work. But the effect in the pictures is not that of a restoration, or as you say ‘the separation of dirt from patina’ but rather a complete stripping resulting in a polished and unnatural surface. The effect is almost as though it was taken to a buffing wheel.
Far be it for me to tell a professional conservator how to do their work. This is a science unto itself, and I have seen amazing work done with ancient metalwork, shipwreck jewelry and coins, excavated weapons, etc. The badge pictured before cleaning displays what appears to be a substantial amount of surviving original factory oxidizing. My collection consists of upwards of 100 pre-war and PSZ eagles, so I am quite familiar with these eagles in their various states of preservation. And seeing the post-cleaning pictures left me with the impression that your badge had undergone an unnecessarily harsh cleaning.
I maintain that such aggressive stripping of the surface (and therefore any original factory applied treatments) is in most instances unnecessary and in fact damaging from the standpoint of value. I have seen similar (and in my opinion disastrous) efforts over the years by well meaning but overzealous collectors. See picture below. So my comments are intended to alert collectors to the dangers of embarking on such endeavors carelessly. As such, your recommendation of the Sekowski book is well made.
Never have I disagreed with a light delicate cleaning if necessary, or - as I have previously stated - the removal of potentially harmful surface pollutants, or encrusted deposits. Obviously the removal of corrosive oxidants is necessary. My point is that the degree of treatment should be proportional to the condition of the badge, in all cases striving to preserve the original surface and patina.
Shiny is not always better. The appearance of a preserved original surface with honest age and patina is a beautiful thing, at least to me.
I have successfully removed verdigris from metal using a little bit of lemon juice and salt applied carefully to only the affected area with a toothbrush or Q-tip. I have also used oxalic acid (powder form “Zud”) with good results. The trick is very careful application to only the affected area, and then a thorough rinsing.
I do commend you on what appears to be a very fine job with the 2DSP eagle. If similar results were achieved with the eagle being discussed then I will humbly refrain from further critique.
Incidentally, do you have any ‘before’ pictures of the 2DSP eagle?
PS You raise some other points unrelated to cleaning that I will address later. But now it’s time to take care of some Sunday afternoon chores . . .