Do you call it cleaning or conserving?

“Cleaning” or “conserving” a coin?

These are two words that might seem to mean the same thing, but they often don’t.

The distinction often boils down to whether a coin is in the hands of an expert, or an amateur.

Doug Mudd, curator at the American Numismatic Association Money Museum, Colorado Springs, Colo., said that the difference is what issue is affecting the coin.

“When you’re doing conservation on a coin, the basic premise is that there is something on the coin destroying it,” he said. “It depends on the coin and its condition. To conserve a coin implies that it needs the help.

“Cleaning a coin doesn’t assume you’re trying to protect a coin from a damaging condition. There are people who clean coins because they’ve toned. There are people who clean coins because they have dirt on them.

“Something like the Saddle Ridge Hoard, where the coins have dirt on them, you can clean them with some distilled water. That’s a different thing than conserving.”

There are many reasons a collector would conserve a coin from further damage, Mudd said.

“For example, if a coin was stored in polyvinyl chloride (PVC) and got its residue on it,” he said. “You want to get that residue off as soon as possible.”

John Krupka, owner of Point Coin, Stevens Point, Wis., said he has seen mainly improperly stored coins turn green because of PVC.

“When PVC was prevalent in the ’80s in coin flips, the PVC would turn the coins green and slimy over time,” he said.

PVC damage is fast and can permanently stain a coin if not stopped through conservation, he said.

“I actually had a set of Lincoln cents that were stored in a coin album containing PVC. Within six months time, they began turning green. PVC is a major detriment to coins.”

Mudd said the metals that most often see damaging conditions that require conservation are silver, nickel and copper.

“With those metals, you have to get the stuff off it, like sulphur,” he said.

“Clay emits sulphur. I saw a demonstration once where the plasters of the coin were displayed with the coin.

“They use clay to change some details on the plasters. The clay emitted sulphur and the coin turned black and flaky. That’s why, with a museum, you use a felt or cloth display that is acid free and inert.”

Mudd said coins can also get “diseases” that eat away at the metal.

“You also get coins that contain copper that get bronze disease, where you really want to conserve them,” he said.

Most coins from sea salvage will need conserving, he said.

“If you’ve got many coins in a mass, you’d need to treat them all in some way,” Mudd said. “The outer coins will have secretions and damage, while the inner coins may look fresh and brand new.”

As opposed to conservation, Krupka said that coins are often cleaned because the owners want them to look better, not to stop any preexisting condition.

“For those that inherit some coins, they’ll want to clean them to make them look nice,” he said. “People will bring in a coin and they plan on keeping it and passing it along to a relative. They’ll ask, ‘What should I clean it with?’

“For a true collector, they already know not to clean coins.”

What people do with their coins is up to them, he said. But if they attempt to clean their coins and they don’t know how to do it properly, the results often dramatically reduce their value, which is the opposite of what is intended.

“I’ve seen coins erased with a pencil eraser, dipped, put in caustic acid or even had fingernail polish put on them to ‘protect’ them,” Krupka said. “If it’s a common coin, it’s not really a big deal. It’ll look hokey though.

Other collectors will not spend their hard earned money to buy a hokey-looking coin. In essence, it is ruined.

“If it’s a 1893-S or 1894 Morgan dollar or a 1916-D Mercury dime, it will be bad.”

Mudd said that cleaned coins are around in today’s market, even in museums, a sort of testimony to past numismatic sins.

“Cleaning was not an issue in numismatics until the 1960s, so coins that had been in a museum may have been cleaned, sometimes multiple times,” he said.

Many older U.S. coins were also cleaned at some point, he said.

“Is it a problem if you have an 1828 Bust half dollar that was cleaned in 1848?” Mudd said. “I tend to look a little less harshly on a coin that was cleaned many years back and it still has its eye appeal.”

When it comes to a coin in your collection, ask yourself: Is this a coin that needs conservation to be saved, or is it better off left alone and its market value preserved?