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Author Topic: To brush or not to brush  (Read 812 times)

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Coin Seeker

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To brush or not to brush
« on: January 15, 2013, 11:51:12 pm »
Hello everyone! I have a question concerning brushing. The only techniques that Minerva and I have used to clean our coins has been soaking in DW or olive oil and manual brushing with only nylon brushes. Is it possible to damage the patina or coins using manual brushing with a nylon brush? We basically have two types of nylon brush. One has stiffer nylon bristles and the other is a tooth brush with softer nylon bristles. I fell that perhaps I maybe damaging the coins using the nylon brush. Thanks everyone!

Oliver

Offline SC

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Re: To brush or not to brush
« Reply #1 on: January 16, 2013, 06:01:38 am »
Oliver,

In most cases you won't damage the coin with a nylon brush.

As in the case of one of yours it might look that way if you remove dirt to reveal a coin that was damaged prior to you getting it.

There is an exception though and that is when you have a very powdery chalky surface.

In spots that can be bronze disease but it is also common with coins found in some soils - especially heavily fertilized soils.  It seems common with uncleaned coins found in British fields and I know from here that it is common in those found in Austrian farm fields.

In my opinion the worst of these are ones where much of the coin is covered with a very thin layer of hard dirt - which can sometimes preserve the surface details in a very fine state - but where this dirt is sitting on the powdery patina.  Cleaning result in a very poor and pitted coin or even a slug as the nice details are really only preserved in the dirt which just pops off.

This is why I always recommend examining the coins dry, before you soak them the first time (as even soaking in DW can harm these coins) or at least drying them out thoroughly and examining them.  This is where poking gently with a toothpick comes in.  You will never get hard dirt off with a toothpick but you can get soft or wet dirt off and more importantly you can test the surface integrity.

All I have ever found to do with these powdery surface coins is to a) leave them as is and put them in your collection, b) give them a gently "polishing" between thumb and finger (sometimes results in a sort of stabilization) or c) give them a gentle waxing.

But unless you have one of these powdery surfaces you should do no harm with gentle brushing.  The safest bet is always to scale up - soft nylon, then stiff nylon, silver wire and then soft brass wire brush

Shawn
 
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(Shawn Caza, Ottawa)

Offline areich

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Re: To brush or not to brush
« Reply #2 on: January 16, 2013, 06:17:44 am »
This is a hard lesson to learn and also why you shouldn't treat coins in large batches. This way you can't keep track of each coin, how the treatment affects it and so can't learn as much from it. Shawn said it already but the worst of these powdery patina coins will look fine but by soaking and brushing you can remove everything but a very thin bronze disc with absolutely no detail left, perhaps 1/3 of the thickness of the original coin. With most coins, some of the surface has turned to patina so you will lose detail when removing it but with these coins most of the coin and all of the detail is in that powdery patina.
Depending on your supplier you may find many of these coins in your lots.
Andreas Reich

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Re: To brush or not to brush
« Reply #3 on: January 16, 2013, 08:36:02 am »
Would this powdery patina your both speaking of be a really soft colored green? I think I may have damaged a coin or two if that's the case. Everything I read said soak the coins in DW and then use manual brushing with a nylon brush. Nothing ever warned me about the powder type patina that can be damaged with manual scrubbing and/or soaking in DW until now. Another question: after cleaning a coin should I put something over it like a wax to protect the coin? Thanks again guys. I'm learning a lot on the forums.

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Re: To brush or not to brush
« Reply #4 on: January 16, 2013, 08:43:57 am »
Yes, that's the typical colour. Usually they're dull but I've seen shiny ones that look like a hard patina unless you know what to look for. After cleaning you should dry them carefully (not too hot), remove any oil, neutralize any acids if you do use them for cleaning and store in a dry place. Use these satchels of silica gel if you live in a humid environment. Waxing (or rubbing with a tiny bit of oil) is useful if you have coins that don't show any detail when completely dry, because of their patina. Also for coins that you cleaned a fake patina off with an acetone bath. They can get very dull and unpleasant to touch (which waxed coins are as well, to a degree). Otherwise I see no sense in it. If you come across any information that the British Museum waxes its coins, that's an old legend going around and not true.
Andreas Reich

 

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