TOOTHPASTE SOAK
Here are 10 coins fresh from an order. They haven't been scrubbed, soaked, picked etc.
What I did was put a big blob of Crest in a container, added distilled water, and mixed the solution up with a toothbrush; until the water was milky. I'm going to let the coins soak for a few days; stirring up the water occasionally, and see what happens.
I think some dirt will be removed, and the coins will be quite a bit easier to work with; since the coins from my Crest toothbrushing experiments were alot easier to work with after brushing.
Coins start at 19.6 grams (dry weight). These are standard grade coins, mostly AE4's, that I got cheaply.
1/09/06
Coins have been soaking for a week (I think- forgot to write it down). I have toothbrushed the coins with Crest after soaking, and here's what I have. Alot of dirt seems to have been removed, and there is a good amount of dirt particles in the water. Please note: This is a different scanner so colors will be a bit different.
Coins now weigh 19.4 grams. That's a loss of 0.2 grams, plus the weight gain due to soaking in water... so probably around 0.4 grams total.
I don't see any patina loss. The coin in the bottom left corner in the above scan has very little patina intact, but by looking at the above scan, the purplish-red metal was peeking through the dirt to begin with; so no fault of the method. The coin in the top row, middle of the above scans has a weak patina, but this can be seen in the above scans as well. Going to do one more experiment with this; and let the coins soak for 2 weeks before I pass final judgment, but I like the results so far.
The coins need more work- but after just one week (or maybe 3 days, I'm not sure) there is a good loss of dirt.
Wondering on the ease of dirt removal, I tried the bright lime green coin in the middle row, right. It has a "powdery" patina, and had the most dirt on it. I spent maybe 30 seconds on it with a new Swiss pin that I just received, and silver brushed it. I only tried the one side. The dirt easily came off. It still needs a little finishing- but egads! Perhaps 45 seconds was spent on this side altogether. I had absolutely no idea that it was a Fel Temp- There isn't any bare metal showing (the scan hints that there is). I've always had difficulties with the powdery patinas anyways.
I've thrown the rest of the coins (9) back into the same container, I'll try to update next Monday. The Fel Temp (above) weighs 1.95 grams.
1/09/06
Another trial, this time with eight coins. The Campgate in the center has some bare metal showing on the obverse. Coins, which have not been pre-soaked, weigh 14.1 grams. The one Fel Temp seems to be a partial-false patina, and the two small coins (bottom row) have just specks of metal showing.
And as a comparison, 4 coins pulled randomly from the same batch. These will be soaked in pure distilled water, and only brushed traditionally, with a toothbrush and soap. Coins start (dry) at 8.8 grams.
The control group now weighs 8.6 grams. Some dirt has been removed (was sitting in the bottom of the container), and details are more prominent.
The group soaked in toothpaste is still 14.1 grams. Details are quite more prominent, even though the weight wasn't decreased. No loss of patina noticable.
And the coins after being toothbrushed. The control group will be toothbrushed with soap, while the toothpaste soaked coins will be brushed using Crest.
Control group now weighs 8.6 grams, so no loss there. Details a bit more prominent; coins still need quite a bit of cleaning.
Toothpaste coins are 14.0 grams. Quite a bit more dirt seems to have been removed with the toothbrushing, than toothbrushing with soap.
The big difference is how easy the dirt comes off- most of the dirt comes off easily - with a Swiss pin on the deeper patches of dirt, and just a silver brush on the rest. The Second coin from the right, bottom row, in the above photo took nearly 30 seconds to finish... 30 seconds.
Update 3/3/06
I had some more lower grade coins soaking in toothpaste/distilled water for a month or so. A couple of the coins ended up having a powdery patina... it was light green and rather thick, and when the pins were used- it came right off. The coins had a darker brown finish over the bare metal- I don't know if this is patina, or some chemical reaction; perhaps the toothpaste ate the patina on these couple coins and left the darker brown residue. The residue did not come off during a silver brushing.
I really don't know if the coins had this powdery green patina under the dirt to begin with or not, but I wouldn't soak coins in a toothpaste solution as a long term soak again.