Baking soda blasting

[parrothead]

[size=medium]Has anyone ever used a micro sand blaster with baking to clean finds?
Just wondered if it would work with out damaging the find..[/size]

 

[nw1886]

Imagine it would be fine for some stuff but wouldn't advise it on a nice high conditioned, older coin.

 

[Ed in SoDak]

We own a Comco micro-blaster and run sodium bicarb in it. I just tried it on some crusty coins and it does remove the surface deposits, but doesn't necessarily help the coin that much. It just blows pits in zinc pennies that have corroded. It tends to remove any shine or luster and may tend to expose the reddish underplating on clad coins. It will get them clean enough to run through a coin sorter.

Perhaps a more gentle abrasive like crushed walnut shells would retain more of the sheen. Soda is the softest abrasive we have on hand, so I couldn't test walnut or talcum or any softer abrasives.

We use our Comco to prepare fossils, but it's also handy for removing paint from metal, etching glass or cleaning car parts or sparkplugs. They cost around $3,000 easy these days, but you can find used ones. If a cheap used machine needs parts, that can bump the price right back up again.

There are cheaper "venturi" hand-blasters you can find for under a hundred bucks.

Don't forget that it is a very messy process unless you do it outdoors or have an enclosed blast cabinet and maybe also an exhaust system!

-Ed

 

[rmptr]

PH, I know guys doing commercial blasting. Their soda is coarse, and it actually explodes upon impact, removing debris upon the surface of the item to be cleaned and causes no damage to the base item. They do not use powder.

Ed's application is probably more suitable for coins, and it doesn't seem like he's willing to advise it strongly.

Primary interest here is to protect coins that may have great potential value which is basically unknown if obstructed with a layer of concretions.

I clean common coins in a tumbler with coarse sand and a bit of soap & borax. Works great!

If there is a chance of collector value, I would advise a soaking method, and perhaps a bit of controlled ultra sonic.

Good luck
rmptr

 

[MK111]

I would use corn cob. We have stell bullet moulds and have used corn cob as a blasting media for years. Walnut shells is too hard. Corn cob is soft so does no real damage to metal.

 

[nw1886]

Corn cob tumbling of coins is actually used as a processing technique by less than reputable coin retailers. The micro "ticks" in the metal mimic original mint luster and obscures slight wear on Extremely Fine and Almost Uncirculated silver coins...namely dollars. At coin shows and conventions, we coin guys, can look through a table full of dollars and pick out the "Place Company Name Here" dollars at a quick glance and we won't touch them.

On old coins...I really like the coins the way they come out of the ground. (Love my ground recovery collection with no apologies!) However...If did find a "RARE" coin, there is a company out of Sarasota FL. that professionally conserves coins for a fee, Numismatic Conservation Service. (This company is closely affiliated with NGC...one of the two most highly respected coin authenticating/grading corporations that all collectors recognize as the bottom line in guaranteeing their investment.) They first analyze the item for the possibility that it can even be improved responsibly. Then will contact you, at that point, to let you know there findings. I have seen some incredible results.

One thing that more detectorists need to realize is that numismatics (coin collecting and study) is a multi-billion dollar industry and, as a matter of need, has developed a deep knowledge and skills base. Coin collectors are the reason there is even any value attached to those little round things we pull out of the ground, and as one, I can tell you stories of literally HUNDREDS OF THOUSANDS OF DOLLARS lost due to rare stuff being thrashed on.

Little old lady walks in to the coin shop... with highly polished,completed sets of UNCIRCULATED Barber Halves,Quarters and Dimes. She had sat down and silver polished the toning off the night before to "Pretty them up". At least $40,000.00 lost. We couldn't really tell as the grades in mint state increase exponentially and we had no way of determining what they were before hand. (Wouldn't have been a stretch at all to have tripled or quadrupled that loss amount.) Her deceased 90 year old husband would have had a heart attack!

Met a guy (from New York State) who was a guest at our treasure club meeting. We all told him how fortunate he was to be able to detect in such an historically rich part of the country and asked him what all he'd found? His list of finds was absolutely incredible! He said that he did bring his Large Cents with him and asked if we'd all like to see them? Out to his car he went and brought back this fairly large, leather bag of his enviable finds. As he poured out his coppers, we were blinded by the brightness of all those "rock tumbler" large cents. (200+ of 'em) Have you ever seen a man almost cry like a baby? (That would have been me.) He was very protective of them so I couldn't get much of a look but...I did see a "Chain", an 1807 over '06, and tons of pre 1814 Classic Head stuff! All...beyond help!

Sorry for jumping up and down on my "stump" (Boldly marked "USE CAUTION") but...the image of that Indian Head penny collection...nailed to an oak board, is still haunting me.

 

[parrothead]

Thanks for all of the information everybody. HH[size=medium][/size]