Let's Define Another Loosely Used Term Around Here - Dipping

Thanks for the response spruett. I agree with the time variable. But I would like to know which chemicals the coin doctors use that cause the damage. There are many different types of acid. I suspect most members of this forum are confused by the general term 'dipped' as I am. I also suspect most are afraid of asking the question for fear of looking like a moron.

That's it! I couldn't remember thiourea. Here's an interesting article concerning "dips":

https://www.coinworld.com/news/prec...ded.all.html

Dipping using EZEST and similar chemicals only works reliably well if 1) there is luster intact and 2) you are dipping high content silver (don't try it on copper, or on billon / other low fineness alloys.)

It literally removes the surface of the coin at a microscopic level; the longer you dip it, the more is removed. It cannot fix damage to the surface other than tarnish and toning (e.g. pitting, corrosion, etc.) Using it straight-up (undiluted) for more than a couple of seconds per coin, and not using acetone or distilled water to rinse the coin before and immediately after, can result in overdipped, ugly coins with spots and stripped luster.

To me: acetone, Blue Ribbon, Verdi-Care and CONSERV are "good" dips when used properly as they are solvents and/or surface protectants. At the other end, products like EZEST (Jeweluster) and MS70 are the usual suspects when we speak of a coin as being dipped in a negative way.

Maybe we need to use the word "stripped" for acid based liquids and the word "dipped" for non acid liquids? I have used EZest in the past with good results on copper and silver and gold.Many years later the coins still look great.I do dilute it with distilled water,about 10%.
John1

As usual, carl hit the nail on the head. I've been pacing around for an hour thinking about acid/base re-dox reactions, inorganic vs. organic,, metals and p-chem. We're not going to get this all worked out on a Monday morning so I'd just to add a couple of points.

Whatever the "dipping agent" is, it's a solvent. They can be the more familiar acidic solvents like EZest or they can be bases, as well. The point is that solvents in common parlance dissolve things. In our case, things either on the surface of coins (verdigris = oxides of copper) or the surface of the coins themselves.

Second point is that opinions on "dipping" change. What is unacceptable to collectors this year may have been just fine in days gone by. If you're an ANA member, go look at some old issues of Numismatist or some of the early coin magazines of the 1960's. You'll find that dipping in all sort of solvents (advertised) was great. If you overdipped, people would be happy to sell you "browning solutions".

Point one is chemistry, point two is more aesthetic and my opinion.

EZest is a mixture of sulfuric acid and thiourea. It is a clear light blue solution. If a silver coin is over dipped, you can see specs of silver in the solution. The solution can be diluted with distilled water, so it is not as harsh on the coin. After the dip of 5 seconds and max of 15 seconds the coin needs to be rinsed in water and some people also rinse with acetone. I have had better luck with black toning doing multipul dips of a couple seconds and pat dry.

This is where I am getting confused when you say using acetone is acceptable. If you use acetone and it removes organic material isn't that cleaning? and isn't cleaning bad?