Behind the Scenes: Coin Conservation - Numismatic News

2022-05-14 00:47:51 By : Ms. Cassie He

I promised to write a few columns on basic coin conservation to help me prepare an educational program on that subject during the coming winter FUN show. Unfortunately, I will not be able to reveal all the proprietary secrets of a conservation lab or most of the chemicals we use, but I know everyone including seasoned dealers will learn something from my columns or the presentation.

Rule #1: Don’t clean your coins! That’s very good advice that most of you should follow. They are not making any more genuine vintage coins. Unfortunately, before third-party grading service encapsulation and in spite of good intentions, large numbers of these coins were being ruined every year by their new owners who didn’t know what they were doing.

By way of introduction, I have been cleaning things since I was old enough to smell the glue we used to build plastic models. I especially liked to clean the precious stones worn by my relatives to restore their brilliance and color. I cannot ever remember cleaning a coin (that was taboo – see Rule #1) until I joined the American Numismatic Association’s Certification Service in Washington, D.C. While there, I was introduced to acetone. Very often, a coin sent in for authentication arrived with crud of some kind around its mintmark. In order to authenticate many of these coins, we had to call the submitter for permission to remove the crud. All it took was a few drops of acetone and a sliver of wood.

On one occasion, a customer sent in a 1936 proof cent for us to determine if it had a satin finish. The coin was bought in an auction described as having beautiful, sea-green toning. It was green, alright. The plastic flip was filled with liquid green PVC that also covered the coin. I conserved it with acetone, we authenticated it and sent it back. Only to be accused later of switching coins as the green color was no longer present. We bought the coin back but after that, the next batch of submission forums stipulated that by signing the forum we had permission to clean it if necessary to authenticate it!

Sometime in the 1970s or 1980s, I began talking about cleaning coins in my grading seminars. By then I had worked in an upscale coin gallery and learned about coin dips, camel hair brushes, etc., as ways to make coins more attractive to sell. Looking back now, I knew very little. My peers and dealer friends were either at the same level of expertise or did not share all of their knowledge, which is understandable. Nevertheless, my skills continued to evolve, mostly through trial and error. Cleaning was no longer taboo and became a necessity in order to get the most money for a coin by simply improving its eye appeal. Eventually, I helped start conservation services at Numismatic Guaranty Company (NGC) and Independent Coin Graders (ICG).

In grading classes, I taught that cleaning a coin was OK when you know what you are doing. Anyone can ruin a coin by improper cleaning; however, if a coin is cleaned properly, no one should be able to tell it was cleaned! Today we call it coin conservation. Conservation preserves it in a better condition for future collectors.

In my experience, most dealers and collectors who decide to clean a coin do not do it properly. Thankfully, our coins are not as delicate as they look, so there is a little built-in cushion for error. Proper cleaning is usually done in steps to prepare the “patient” (a word used by stamp authenticators for the object they are working on). This may involve all sorts of chemicals, materials and methods of actual contact with the patient’s surface. This is where it gets complicated and proprietary, but I’ll take you a little over the line. In one online forum, I posted that acetone is not the wonder chemical that many collectors believe it to be. That’s because on a scale of the most common chemicals I use in the lab that goes from the letters “A” to “N,” acetone would be represented by the letter “D.” I’ll spare readers their guesses for the previous letters “A” to “C” and tell you they are tap water, distilled water and deionized water.

The steps involved with cleaning any coin can be thought of as chemical, mechanical or a combination of both. Mechanical cleaning involves removing contamination on a coin with a tool of some kind. Copper specialists often recommend a rose thorn or camel’s hair jeweler’s brush. Chemical cleaning needs no explanation. Conservation can involve the entire coin or just a small part of it (spot conservation). Many of the steps involved with proper cleaning are best done using a stereo microscope and fluorescent light.

Figure 1: Developing corrosion spot on Jefferson nickel.

Figure 1 is an example of simple spot conservation. A hard, green corrosion product has been removed from the cheek of a Jefferson nickel in a way that did not change the color of the rest of the coin. I’ve enhanced the color of the “before” image to better show the green spot.

One very important conservation tip I’ve learned is to keep the coin wet while removing debris. This eliminates most of the chance of putting a hairline on the coin from the grit you are removing. Most of the treatments we do to improve the coin without making it look improperly cleaned are done in one of the pre-dip stages when the patient is being prepared for its final dip if an overall cleaning was needed.

I’ll write again on this topic soon, but for now remember the objective of proper cleaning is to leave no evidence that it was conserved. Until then, don’t clean your coins unless you have the experience.

Each day at the grading service, I see many coins with impaired eye appeal.  Proofs are hazed over, spotted, splotchy, discolored and fingerprinted while the copper coins are dirty, often with green residue.