HYDROGEN PEROXIDE 3% REVISITED
Osco had a sale on quarts of hydrogen peroxide 3% for .99, so I bought a half dozen to play with while waiting for my gallon of 35% to arrive (It arrived today). Unforunately, I did not take before shots of the coins. I began with 200 coins or so, in different stages of cleaning. Some had been soaking in distilled water for a month, some I had partially cleaned, some had just arrived, some came from my fishtank- etc.
I have been changing the solution about 3 times a day. I dumped 20-50 (depending on size) coins in containers- without a lid. This seems necessary- the solution reacts better when exposed to air.
After about 5 days, I started preliminary cleaning on the coins. Especially when it came to the "culls" from an English lot, I was quite surprised. I think my first trials some months ago were in a sealed container- and I didn't change the solution often.
The English culls (which for me looks like it will have about a 70% ratio for keepers) really responded to this method. Dirt varities are more numerous in these English coins than most lots; from black mud to almost a dry sand and everything in between. They all are being removed with ease.
Basically, after the 5 days or so, I'm dumping out a container, letting them air dry; then using my larger diamond pin as well as the ball, to remove most of the dirt. Each coin is taking perhaps 2 to 3 minutes for this. Then I use the soft brass brush on them, which removes quite a bit of lingering dirt. Then I throw them back in to soak- but separated from the other coins; so I know which ones are close to being done. Most of the dirt comes off easily, with little or no pressure involved. I'm just using the side of my pin to wipe the dirt off.
Of course, with any lot of coins- there are plenty of "special" coins. Especially with the English coins- there are partial patinas, false patinas, some kind of white-lime like encrustations, basic red/green encrustations etc. The hydrogen peroxide doesn't seem to affect the red and green encrustations at all. It seems to be dissolving the white lime/calcium whatever some- but very slowly. This new encrustation, that I haven't encountered before, is on a nice Theodosius II campgate unfortunately. The obverse is clean and well detailed, but the reverse has this stuff covering much of the campgate and exergue. The solution doesn't seem to be eating the partial patinas, and the false patinas (dark outer "shell" that really isn't a patina in the basic sense; when removed yields a pitted slug of bare metal) seem to be holding intact.
I don't understand why many of these were in a cull lot really. Some are holed (you'll probably see these on ebay soon, when I'm done), some are chipped and broken (these I understand as being culls), some are lightly encrusted (and I do mean lightly) and others are just dirty. And of course you have the English patinas to deal with- but this is unavoidable in English found coins, which normally sell at a premium. There was a Byzantine follis that was holed- but it was also covered in mud, some 8mm thick on each side. Why was this deemed a cull? The dirt basically brushed off with my pin- and under the mud, I found a holed follis that is VF+ condition. I digress...
The other day, before work, I was able to finish about 40 coins in 3 hours- while watching tv. This includes time for drying, more detailed cleaning around letters and such, silver brushing, radial brushing, micro fiber cloth and finally Renwaxing. So perhaps 5 hours of cleaning (actual time spent working on them) for around 40 coins. That's not too bad.
So- this procedure (which seems to be working safely- but has little or no effect on encrustations) is basicially-
Soak coins in an open container with changing solution 3 times a day
After a few days, do some preliminary cleaning with your favorite tools, then resoak for a day or two more
Revisit the semi-cleaned coins and finish them up
Of course, not all coins will be easily finished- but from my trials, the majority will be done by the second cleaning