How you guys dry your Coins after cleaning them?

[MrZun]

Sorry for my bad english.

When you soak and then rinse them in distilled water, what you guys use to dry them?

I usually put the Coin in a cotton cloth and gently dry It by gently patting the other side in the Coin without rubbing it and the edges aswell. Then i leave the Coin in the cabinet with a tiny bag of silica gel above It to suck the humidity of the coin and then i close the tray. I was wondering if i did the right thing. Should i have left the Coin in the open air for a while before? Because for some strange reason, 2 days after this, all my coins in that tray at the same time got a bit darker and a bit yellowish, was It because of the humidity of that single Coin? I tought the sílica gel would be enough and i usually leave 2 bags of It inside each tray.
Is It safe to use an hair dryer in the Coin? Should i use hot air or cold?

[-monolith-]

I just put my "washed" coins on a cotton cloth in front of a fan for about an hour each side then your good. I know acetone will completely remove any moisture as well. It's highly unusual for all the coins to darken in just a couple of days. 

[MrZun]

1 minute ago, -monolith- said:

I just put my "washed" coins on a cotton cloth in front of a fan for about an hour each side then your good. I know acetone will completely remove any moisture as well. It's highly unusual for all the coins to darken in just a couple of days. 

Perhaps It was Just my climate. I live in a tropical country and its hot and humid or hot and dry. 

[Orange Julius]

I put the coins in foil and put them into the oven at about 275 degrees for about 20-30 minutes. This dries out, not just the surface but any cracks, crevices and soft spots in the metal. As even lead’s melting point is at over 600 degrees, it me it seems safe for coins and has no effect on their appearance.

[JAZ Numismatics]

1 hour ago, Orange Julius said:

I put the coins in foil and put them into the oven at about 275 degrees for about 20-30 minutes. This dries out, not just the surface but any cracks, crevices and soft spots in the metal. As even lead’s melting point is at over 600 degrees, it me it seems safe for coins and has no effect on their appearance.

The problem with foil is that it traps the moisture in, and the coins don't dry as well as they could. I was advised to simply put the oven on its lowest temp, typically 170 F, and just let them sit there for an hour. Flip them over once. 170 is enough to evaporate all the water without damaging the coins.

[Bonshaw]

14 minutes ago, JAZ Numismatics said:

The problem with foil is that it traps the moisture in, and the coins don't dry as well as they could. I was advised to simply put the oven on its lowest temp, typically 170 F, and just let them sit there for an hour. Flip them over once. 170 is enough to evaporate all the water without damaging the coins.

If you heat an ancient coin, I would strongly advise you to keep the temperature pretty low. Definitely 170 rather than 275 (which was mentioned in an earlier post).

I worry about any unmixed inclusions, or any spots in coins that have a different metallurgical makeup. Rapid heating / cooling combined with differential thermal contraction can lead to stress, and possibly cracking or further crack propagation. Just because you have done this before with no problems doesn't mean that the next coin, with an unknown inclusion, is safe from cracking.

I settle for forced air drying from a fan (on both sides) followed by storage with a gel pack for humidity control and a humidity meter to make sure it all stays below 30% RH.

Edited November 1, 2024 by Bonshaw

[MrZun]

4 minutes ago, Bonshaw said:

If you heat an ancient coin, I would strongly advise you to keep the temperature pretty low. Definitely 170 rather than 275 (which was mentioned in an earlier post).

I worry about any unmixed inclusions, or any spots in coins that have a different metallurgical makeup. Rapid heating / cooling combined with differential thermal contraction can lead to stress, and possibly cracking or further crack propagation. Just because you have done this before with no problems doesn't mean that the next coin, with an unknown inclusion, is safe from cracking.

I settle for forced air drying from a fan (on both sides) followed by storage with a gel pack for humidity control and a humidity meter to make sure it all stays below 30% RH.

Should i put the Coin in a Acetone Bath before drying It in a fan?

[JAZ Numismatics]

2 minutes ago, MrZun said:

Should i put the Coin in a Acetone Bath before drying It in a fan?

I would say yes. Acetone will dissolve organic compounds, but I don't believe it will have any effect on the patina. That's been my experience at any rate.

[MrZun]

30 minutes ago, JAZ Numismatics said:

I would say yes. Acetone will dissolve organic compounds, but I don't believe it will have any effect on the patina. That's been my experience at any rate.

Alcohol isopropyl does the same as Acetone?

[MrZun]

Just now, MrZun said:

Alcohol isopropyl does the same as Acetone?

Kinda hard to find pure acetone

[JAZ Numismatics]

23 minutes ago, MrZun said:

Kinda hard to find pure acetone

Any hardware store should have it.

[MrZun]

3 minutes ago, JAZ Numismatics said:

Any hardware store should have it.

In my country, You need permission from authorities to buy it, since It can be used to make drugs 

[Nerosmyfavorite68]

This is a great question.  It's often advised to soak a coin, but it's never really stated how to properly dry them, which is pretty important.

[JAZ Numismatics]

17 minutes ago, MrZun said:

In my country, You need permission from authorities to buy it, since It can be used to make drugs 

You don't really need acetone unless you're trying to clean off organic material or PVC deposits. The only time I used it was to clean some silver coins that had become green from sitting in PVC flips for many years. Otherwise, heat drying should be good enough. I can't say anything about isopropyl alcohol as I've never tried it.

Edited November 1, 2024 by JAZ Numismatics

[Orange Julius]

3 hours ago, JAZ Numismatics said:

The problem with foil is that it traps the moisture in, and the coins don't dry as well as they could. I was advised to simply put the oven on its lowest temp, typically 170 F, and just let them sit there for an hour. Flip them over once. 170 is enough to evaporate all the water without damaging the coins.

I usually make the foil into a fun bowl with the top open to allow evaporation. Yes, 275 may be higher than needed. But I’m not putting anything valuable in the oven. These are scrappy LBRs that I clean. I would absolutely be a bit more careful with anything of value or silver alloys. 275 sounds hot… but those crusty Valens and Valentinian coins handle it fine. 🔥😁

[Dwarf]

7 hours ago, MrZun said:

and then i close the tray

What cabinet do you use ?
If you use a wooden cabinet with the wrong wood - this might become a disaster.
The same goes for bad plastics

[Bonshaw]

6 hours ago, Orange Julius said:

I put the coins in foil and put them into the oven at about 275 degrees for about 20-30 minutes. This dries out, not just the surface but any cracks, crevices and soft spots in the metal. As even lead’s melting point is at over 600 degrees, it me it seems safe for coins and has no effect on their appearance.

@Orange Julius Whatever you do, NEVER heat gold coins in aluminum foil.

At high temperatures, gold will react with aluminum, forming different nasty intermetallics.

I have personally had the bad experience of heating pure gold wires in aluminum foil in a furnace and seen the growth of the "purple plague" - AuAl2, which was indeed a visibly purple insulator. Fortunately, this wasn't with ancient coins (it was to increase the conductivity of the gold wires).

There are a variety of other "plagues" as well with different stoichiometry, like Au5Al2 (white plague).

This was at a higher temperature than 275, but it still happens well below any melting point, and I wouldn't risk it. Whether it occurs depends on other factors as well, like humidity. It can even occur in some cases with aluminum wirebonds on gold pads on silicon chips at room temperature. The semiconductor industry has somehow made those joints stable, but I have seen aluminum-to-gold wirebonds made by non-experts go insulating in humid conditions.

Edited November 1, 2024 by Bonshaw

[Dafydd]

3 hours ago, MrZun said:

In my country, You need permission from authorities to buy it, since It can be used to make drugs 

Maybe look for nail varnish remover, sold in smaller containers so not much use to drug processors, check the ingredients. Your posts make fascinating reading @MrZun and you are doing fine with your English and forgive some of us for reading the wrong intonation in your posts. 

[mr. wiggles]

Chemically speaking acetone and isopropanol are chemical similar. IPA boils at a higher temperature than acetone, but both are miscible with water.

On the plus side your coins will be sanitized when you’re done! 

[Alegandron]

This works for me...

[MrZun]

Well, i Just did this: one hour of the Coin close to the fan in high speed. One hour in each side and then one hour in each Edge. Then i Just put the Coin back in the tray with a bag of silica gel close to the coin. It worked well. Make sure you dry the Coin in a clean, soft and dry cotton cloth First without rubbing it, Just gently patting It. The Coins in my tray are normal, it was Just my mind being paranoid after cleaning them other Coin, all is well.

[DonnaML]

On 11/1/2024 at 3:23 PM, JAZ Numismatics said:

You don't really need acetone unless you're trying to clean off organic material or PVC deposits. The only time I used it was to clean some silver coins that had become green from sitting in PVC flips for many years. Otherwise, heat drying should be good enough. I can't say anything about isopropyl alcohol as I've never tried it.

For removing PVC residue, how long should a coin be bathed in acetone? Thanks.

[JAZ Numismatics]

1 hour ago, DonnaML said:

For removing PVC residue, how long should a coin be bathed in acetone? Thanks.

I had a few King George rupees with lots of PVC residue. Soaking wasn't enough. I had to rub them gently with a Q-tip. They were only worth their bullion value, so there was no danger of damaging a valuable coin. But I got them clean and they were still nicely toned, unlike dipping them in silver cleaner. I also cleaned a few scrungy LRB's, but again, I used a Q-tip. Jusk soaking doesn't seem to have any effect.

[DonnaML]

41 minutes ago, JAZ Numismatics said:

I had a few King George rupees with lots of PVC residue. Soaking wasn't enough. I had to rub them gently with a Q-tip. They were only worth their bullion value, so there was no danger of damaging a valuable coin. But I got them clean and they were still nicely toned, unlike dipping them in silver cleaner. I also cleaned a few scrungy LRB's, but again, I used a Q-tip. Jusk soaking doesn't seem to have any effect.

Thanks! How long did you leave them in the acetone before using the Q-tip? I have some old U.S. silver dollars that were kept in plastic pages in a 3-ring binder for about 50 years, and some of them definitely have green residue on them.

[JAZ Numismatics]

2 hours ago, DonnaML said:

Thanks! How long did you leave them in the acetone before using the Q-tip? I have some old U.S. silver dollars that were kept in plastic pages in a 3-ring binder for about 50 years, and some of them definitely have green residue on them.

Try soaking an hour, then see it the Q-tip works. Acetone is pretty strong stuff. Use gloves and make sure the room is ventilated. Also, get pure acetone from the hardware store. Nail polish remover has added compounds as fragrances, which might discolor the coin.