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FORVM`s Classical Numismatics Discussion Board  |  Numismatic and History Discussions  |  Uncleaned Ancient Coin Discussion  |  Topic: If you can't say something nice, don't say anything at all ? 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: If you can't say something nice, don't say anything at all ?  (Read 445 times)
Ken W2
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« on: July 20, 2020, 12:36:45 pm »

Well, perhaps the lack of any responses to my request for input in my last post "advice on prelim and other abrasives" reflects the old saying that is the title of this post.  Being surprised by the lack of responses I reviewed some older threads about "polishing" and see that some are very critical of it-- perhaps mostly when it is applied to bare metal. So, that leads to these questions:

1) Is using prelim to clean away some of that last kind of film of dirt considered polishing ?

2) Is using prelim to smooth out light cleaning marks in the patina (not the bare metal) considered polishing ?

3) If the overall goals of cleaning dirt caked RICs are to achieve attribution (an objective standard) and have a coin with a pleasant eye appeal (a subjective standard), how is using prelim to clean dirt and smooth out cleaning scatches objectionable ? 

After all, we are already in the realm of "cleaning" coins-- an almost universally accepted no, no in the coin collecting hobby.  If we were acting based on general coin collecting protocols we would never lay even a brush to our coins, much less a dental pic, diamond encrusted bit, or needle.  If the answer of some is, "well you must remove the dirt to identify the coin," then those persons must stop cleaning the very moment they achieve attribution.  Beyond that, additional cleaning is merely improving the appearance-- the same goal I have in using prelim.  If prelim is good enough for museum grade artifacts, is it not acceptable in our area of coin collecting ?

Ken W2               
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v-drome
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« Reply #1 on: July 20, 2020, 04:46:39 pm »

It is difficult to tell from your photos what might and might not be useful in treating your coins.  However, the problem with any kind of brushing is that you are essentially removing material from the high spots and thereby lowering the relief, which is part of what makes a coin good or bad.  Of course there are many variables and each coin is a different case, but in general it is better to do too little than too much.  There is also a big difference between coins that have a solid collector's patina, which starts on the surface of the coin and protects it inward, and complex corrosion which starts within the crystalline structure of a coin and bubbles outward, destroying the surface.  I have had coins which were so heavily corroded that mechanical cleaning simply was not possible and have had to resort to chemical means, but this is a last resort.  It is okay if the coin doesn't look "perfect", old coins aren't necessarily supposed to!  A little bit of oil (olive or mineral, light coat or short soak) might help even out the appearance of the surface without abrasion.  It is usually reversible if you don't like it, but it can also cause the surface to darken and lose that nice green color.  Like I said, every coin is an individual case.  So, less is better, you can always do more later.  In the meantime you may come to like the coins just the way they are and decide that they are "perfect" just the way they are.  I think people on this site are reluctant to tell you what to do because if it doesn't work out, and often it won't, we don't want to take the blame!  Good luck!

(edited 7:55 pm)
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Mark F
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« Reply #2 on: July 21, 2020, 08:47:36 am »

Ken,

You very nicely quoted something my (now gone) mother POUNDED into me when I was younger involving keeping my mouth shut!

In my case it is not disagreement with use of Pre-Lim, but simply not having any experience with it. I do agree, though, it is a very touchy subject. After your post and some googling I actually ordered some Pre-Lim to try for a specific situation, which I'll detail later.

1. I noticed that Pre-Lim does have some adherents within the ranks of museum conservators, but I could not find any published info from them about it's use on coins. Other metal artifacts, yes, but coins, no. The use of harsher methods is more typical (from my reading) for spear points and bracelets (at least not gold ones) because proper classification of the object, especially if it involves an on-going archaeological dig, outranks almost all other goals. Thus use of harsh chemical stripping or electrolysis to enable faster identification. This is referenced in quite a few papers and books I've read on conservation (at least those published 15 or more years ago).

2. Coins are usually (though not always) treated somewhat differently. I suspect it's because they occupy a special place between useful metal implements and works of art. The closer a person is to viewing cons as artistic artifacts, the more likely it is that ever more gentle cleaning methods are used, and that would normally preclude the use of ANY abrasive polishing agent.

3. Someone who is closer to the "coins are art" would then clean coins very gently. Furthermore, they would normally clean coins ONLY until the coin could be clearly attributed and no further. Examples are coins that are cleaned but have some deposits remaining.

4. I used to be more in that camp, but have recently (in past year, or so) moved further in the opposite direction. I am now more interested in trying to get a coin to look the best it can be, considering its specific state, which can vary from very poor to pretty nice. NOTE that this does NOT mean getting a coin completely clean because many coins look better AND are more legible if a bit of stuff is left surrounding or within specific areas of the coin (great examples are desert patinas and other coins that have a bit of dusty stuff remaining).

5. So I didn't reply because of lack of experience with Pre-Lim. I also am personally VERY selective anymore regarding applying ANY liquid to a coin. I have absolutely ruined some coins with nothing but distilled water. If any surface or patina is showing, I clean a coin almost exclusively mechanically. if completely dirt covered, I'll use gentle water-based chemical solutions (another topic) to loosen things up.

6. The situation I'm interested in where Pre-Lim might be useful is this one: late Roman coin, dirt covered exclusively. Once I begin cleaning it with my tools, the only liquid that normally touches the coin is saliva (don't ask). So I scrape and scrape and poke and poke, and scrape some more (under binocular microscope). Eventually I get to a place where ALMOST everything is clean, but sometimes there's a bit of stuff clinging to the surface that I just can't seem to get off.

7. I've been trying various methods - some of them involving liquids - and some using abrasive tools such as fiberglass pens used for cleaning smutz off electrical connections. I noticed that Pre-Lim is basically a slurry that includes silica abrasives, which is sand of some very small size, so it is not conceptually different from me using fiberglass pens. I worry about the control I'd have with Pre-Lim, but that's why we experiment on culls, so I'll see when it gets here. My concern about abrasives is that they could "round off the edges" of design elements on the coin and damage its appearance and potentially leave visible marks (my goal is always to leave no marks visible under my microscope, though after 18 years cleaning coins I don't always succeed).

8. Yeah, most people would consider removing marks within a patina with an abrasive substance to be polishing. My goal is always leave no marks, but as I say that, it's a GOAL, and not always achieved. If you are going to clean coins, you will almost always damage something you would rather not, which is why we start gentle and only pull out the steel punch and hammer for certain problems (yes, have actually used that, but a topic for another day).

Last topic for now and addresses your last paragraph. Dude, just tell the modern-coin-collector-no-cleaning-bullcrud to pound sand. They have their world and we have ours. we mostly don't even speak the same language. Theirs is the world of lovely coins viewable only through sealed plastic cases, where a fingerprint can cause a coin to loose half its value. Our coins are objects we TOUCH, and treasure.

Thanks for your post, Ken. I haven't posted much here in the past 15 years and was completely focused on other things for most  of that time though I was active on the boards before that. Now thankfully retired. Your post got the old blood pumping so maybe I'll post some of the stuff I'm working on lately. I'm just too darned wordy...

Mark
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Ken W2
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« Reply #3 on: July 21, 2020, 11:48:46 am »

V-drome and Mark:  Thanks for your replies.  I do like these coins in their present state, but I think a little more work will improve them (famous last words).  I'm mostly concerned about the silvering on the two captives coin.  Sorry about the poor pics.  I just have not reached the point of spending the money on a DSLR camera to produce good photos (I'm using an Iphone 6 with a not so great camera).     

Mark, the situation you describe in paragraph 6 is where I am with the silvered two captives.  Mechanical cleaning is complete, but there is a patchy, kind of film of dirt, or dirt imbedded in/adhered to the very surface of the silvering or patina.  I know the prelim will remove some of it, and maybe most of it, I'm just not sure the silvering is stable enough to take any dremel brushing.  V-drome, I'm not worried about causing wear to the relief-- prelim is a very, very, very mild abrasive, and I'm making only a few passes using a soft bristle brush in a mini dremel (not more than 10 seconds total on each side), but again I am concerned I might knock some of the silvering off.   

The bronze Follis has a solid patina and so I'm less worried about it.  But, it is why I was asking about something more agressive than prelim, but still a mild abrasive. Something a little more agressive may do a better job of removing the "film" of dirt and smoothing out cleaning marks.   

The more I think about this, from the minute we start cleaning a coin using abrasives is what we do.  If we have no problem using diamond encrusted pins or other tools, we shouldn't be concerned about using prelim or similar substances to very, very finely smooth our own cleaning marks from the surface of the patina and perhaps remove a little more dirt.  Mark, I clean under 10X with a stereo scope too. I've used prelim a lot.  It is effective at smoothing the "fuzyness" in the surface of the patina and cleaning marks, as long as they are not too deep. You will not be able to see brush marks from using prelim at 10X and probably 20X.   My educated guess is you will need much, much more magnification to see any brush marks from using prelim.

Please do post some pics of your work and let me know how you like the prelim.  It can be a pain to clean it out of crevices before waxing, but to me that is its only drawback.  I'll post photos of how the two catives coin turns out.  Thanks again.

Ken   
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Mark F
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« Reply #4 on: July 21, 2020, 01:52:52 pm »

Ken,

Have you  tried Pre-Lim with something milder than the soft (brass?) brush? I have used some old dental brushes for years at slow speed to coins after I apply wax. Those brushes are some kind of natural fiber - I think "boar" or similar. Likewise, have you ever tried a soft cloth "polishing" pad instead of the brush? Just curious what alternatives you played with to end up with the brass brush (I know they are "soft" but still don't like using them much on this end, though I own several). Perhaps a softer attachment may offer a bit more control to avoid damaging the silvering in your final cleaning steps. Just a thought.

I don't use a dremel often as just too fast. Instead I use an old dental desktop power tool that at this point is at least 60 years old. Grabbed it out of my father's dental lab when he died. Still cranking along and belts are available for it. It can go very slowly or quite fast as needed. Easy control via foot pedal.

Good luck,

Mark
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Ken W2
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« Reply #5 on: July 21, 2020, 03:58:21 pm »

Mark:  Oh gosh, my bad.  When I say "SBB" I mean a soft bristle brush-- natural fiber (or synthetic fiber but soft like natural fiber). V-drome must have thought I meant brass too given his concern about wearing down relief.  I tried using brass under running water but could never get the hang of it and almost always removed too much patina without removing the desired amount of dirt.  I don't use brass brushes anymore except on iron Civil War artifacts, and even then sparingly.

You did just make me think of this:  If folks accept the use of brass brushes as a proper cleaning technique-- which surely must leave marks visible under magnification-- I don't see how they could logically object to the much less aggressive use of prelim applied with a SNFBB (soft natural fiber bristle brush).

On my RICs, after mechanical cleaning, I use a medium bristle brush-- the ones with black plastic fibers-- in a mini dremel on low (8,000 rpm I think) in a really soapy water solution, then move to prelim with the SBB. But I think I will skip the medium bristle brushing on the silvered coin and go straight to prelim.  That dental rotary tool sounds nice.

Ken     
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PMah
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« Reply #6 on: July 21, 2020, 08:35:54 pm »

Not to jump in on a long thread without good reason, but I have an observation.
    I absolutely love Dremel tools, I have 2 corded and 1 rechargeable, plus the extensions, drill press and a zillion tips.  I'd never go near a coin with one.
  The lowest speed is about 5000 rpm, perhaps slightly less than that if the rechargeable battery is low.  The circumference of a brush tool is about the length of a toothbrush head, very roughly 1 inch.  So, that's a minimum of 80 strokes per second with a soft toothbrush by hand.  That's what, 10 or 20 times faster than "vigorously" hand brushing?
      So, ok, there's quite a bit of a difference in the dynamics, but, for me, you can only accidentally go one stroke "too many" with a hand tool, but you can go many, many more with a power tool.  And practice improves any technique, but what do you "practice" on?   I'd suggest trying to clean a grimy old US copper cent and being a bit inattentive for a full second with a power tool ... and seeing if you like the outcome!
     I have practiced a dremel on many modern surfaces,  but none seem like an ancient coin.  I think one time I demo'd cutting open a slab using a dremel,  but that's as close as I'd get to a coin.
     The coins took centuries to build up the material some collectors want to remove, but is it really worth the irremedial risk to get the job done in 5 minutes or even 5 days?
  Be well, everyone. 
 
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Mark F
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« Reply #7 on: July 21, 2020, 10:56:32 pm »

Hi Paul  and the more the merrier!

I understand the hesitation regarding approaching a coin with a power tool, though I'd like to offer some of my thoughts.

I think it very much matters what type of tool is used in the power tool that actually touches the coin. My understanding from Ken is that he uses two tools in his Dremel, both varieties of brushes, one being a head with nylon bristles that are somewhat stiff and one with natural bristles that are quite soft. I've tried to clean (years ago) dirt from coins with similar brushes, but it is slow and very unsatisfying. And it is very easy to cause unintended harm, as you mentioned. Most genuinely uncleaned coins have surfaces so dirt packed that most of the time the soft bristles that ken uses wouldn't even scratch the surface. They are not as aggressive as you might expect.

I use a power tool (or rather several of them as I am a bit tool-rich at the present) for very limited purposes around coin cleaning. I use a soft, natural bristle brush (from boar's hair) in my dental lab tool to do a final clean up of a coin around all its devices, getting into crevices, etc., before I apply Renwax. Once the wax has dried, I then use a different tip which is a small, tightly bound bundle of cotton flannel that I then use to polish the wax. Both of these tasks happen at very slow speed (my tools have manageable control, speed wise, from 0 to 18K RPM). Having used these these tools this way for about 15 years with no harm I'm very confident in the safety of this method.

All that said, I do know coin cleaners who are much better than me who use powered tools in many more ways and many times their results are satisfying. It is not so much the results that I reject but the process; I like to go slower and calmer, listen to some music and glue myself to a microscope. That is how I want to experience cleaning. I've seen some people go at a coin so vigorously it makes me cringe, but it's a very personal decision, and it's a pretty big room as long as everyone respects the coins.

Paul - how do you clean your coins? How do you decide when you done? How do you decide when to clean a coin and when not to? What's your method or process? I bet you know something many of us would want to know, so throw something out, though it might be better to start a new topic so your input doesn't get lost in a long thread.

Thanks again,

Mark
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Ken W2
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« Reply #8 on: July 22, 2020, 10:27:00 am »

Hey Paul and Mark:  Absolutely, the more the merrier.  To clarify, I only use the battery powered mini dremel and soft-medium bristle brushes at the final cleaning stages just before Ren wax.  I use DW soaks and brushing with a toothbrush as the first steps (removing the loose and easy dirt), and then proceed to mechanical cleaning with diamond coated pins in a pin vise at 10X under a microscope.  When I reach the point I'm satisfied with the coin (generally, as shown in the pics in my post about prelim and other abrasives), I then use the dremel and medium brush in soapy water and then apply prelim with the soft brush.  I'm not getting much dirt off with these latter steps, but I do get some dirt off and smooth the surface of the patina to eliminate most cleaning marks.  After drying through a combination of solvent dehydration (soaking in 91% to 100% alcohol) and low heat in the oven, I then apply Ren wax also using a soft bristle brush in the mini dremel.  However, I'm considering moving away from waxing.  I do think waxing brings out color and detail, and protects the coin from moisture, but it does give an un-natural "shiny" appearance.

I am thinking about trying a brass brush in the mini dremel again, though.  As you know, there are some coins that just won't be cleaned by less agressive measures, at least not in our lifetimes.  Now, those coins go in the discard pile to be chemically stripped when I can get to them. That is a last resort.  While many of those coins will then be easily attributable, very few have much eye appeal.  I've tried Jax and liver of sulfer to darken stripped coins, but again with limited success.  So, I may try the dremel and brass brush again on this type of coin.  If I could master that technique to remove the dirt and remove only some of the patina and mostly on the high points, thereby creating some contrast between the devices and fields, I might find that more appealing than stripping them.
   
Thanks for sharing your views and techniques.

Ken   
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agord
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« Reply #9 on: July 22, 2020, 05:49:22 pm »

Where you use PreLim I go to a 1" felt wheel in my dremel. This seems to remove the last cleaning marks in the patina.

Gord
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« Reply #10 on: July 23, 2020, 08:29:47 am »

I didn't reply earlier because one can tend to get caught up in semantic and philosophical differences.

Removing lines in the dirt is clearly cleaning. 

Removing lines in the metal is clearly smoothing

But what about the patina?

Patina is treated as sacred, in theory - part of the metal.  But in reality it is not entirely sacred.  A great many coins in great and famous collections were stripped of their patina when originally cleaned.  It is now recognized that this should be avoided if at all possible, but even now there are times when it is not possible and the best choice is a decent coin without patina instead of an unrecognizable blob with.  In addition many coins have a patina that is horrible.

I have used almost all the mechanical techniques discussed (though not pre-lim). 

My own philosophy is to not worry when removing dirt - though like others have said there is often no need to remove it all.  I try to totally avoid affecting the metal in any way.  If I scratch it I leave it.  As for the patina, that is where I try to be very careful.  Often it is hard to tell if you scratched only into a thick layer of patina or if you scratched through the patina and into the underlying metal.  If i have scratched the patina I will often try to gently smooth it out but am always ready to abandon the effort and leave the scratches if it looks like I am affecting the original metal.

SC
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SC
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Mark F
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« Reply #11 on: July 23, 2020, 07:57:55 pm »

Where you use PreLim I go to a 1" felt wheel in my dremel. This seems to remove the last cleaning marks in the patina.

Gord


Gord,

Do you use the felt wheel dry or with some liquid or other substance? Very curious as haven't encountered that before, though I use a very similar device after I wax certain coins.

Mark
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Mark F
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« Reply #12 on: July 23, 2020, 08:10:55 pm »

Shawn,

You make a good distinction RE patina vs. coin. I've seen coins for sale that noted that surfaces - that are completely covered by a nice patina - are noted as being smoothed. I know what they mean by that, but I've never let it dissuade me if it's a coin I wanted.

I do start every cleaning attempt with a goal of doing no harm, but sometimes it's hard.

Mark
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« Reply #13 on: July 24, 2020, 03:56:01 pm »

I use a felt wheel to buff up waxed coins. 

Never found that the wheel was particularly useful for anything else.

SC
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(Shawn Caza, Ottawa)
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« Reply #14 on: July 24, 2020, 06:30:03 pm »

I use the felt wheel dry, mostly to smooth small marks in the patina. Works best on coins with a relatively thick green patina.

Gord
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« Reply #15 on: July 25, 2020, 05:23:00 pm »

Ave!

Concerning all of the above, you all need to take a step back, okay?

PreLim is fine but not the best way to begin, just saying.
 
For cleaning any individual silvered issues, always begin with the very least invasive process; IE., a simple paste of Backing Soda. Make a thick past of the same and then apply it to a thin cotton towel, press down hard and apply the to each surfaces, rinse, wash and repeat as seen in the next coin below.

PriLim paste - The grit is so low you can use it on your car's paint to restore it to as original, you know?

I use a felt wheel to buff up waxed coins.  Never found that the wheel was particularly useful for anything else.
SC

Shawn, perhaps you have never used the felt wheel added to the 1600 grit diamond dust?

Best regards to all,

Kevin


* Kens coin copy.jpg (58.72 KB, 752x454 - viewed 11 times.)

* AR Gra .jpg (112.69 KB, 1000x614 - viewed 7 times.)

* Fent and powder .jpg (36.73 KB, 900x497 - viewed 6 times.)
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Ken W2
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« Reply #16 on: July 30, 2020, 12:52:25 pm »

Thanks to all for your input.  I used prelim on the silvered Connie.  It smoothed some of the fuzziness and slightly darkened the color.  I'm happy with it.  I also used prelim on a few recently cleaned bronzes and am dissappointed.  It did remove a little dirt, most of the fuzziness, and some cleaning marks in the patina, but not all of them. You cannot see the remaining marks under low magnification, but they are obvious at 10X.  So, I'm back to my original problem. 

Gord and Kevin--can those felt pads get into tight spaces like between letters ?  Also, there is a youtube video by Peter Kennet showing final cleaning in which he says (I think) he soaks in sodium sesquecarbonate (maybe a 2% solution?) before he cleans to slightly soften the patina.  I'm thinking that might make the prelim or other techniques more effective at removing cleaning marks.  Anyone try that ?

Am I obsessing too much about cleaning marks ?  Are they just something that must be accepted in our area of the hobby, or perhaps I just wasn't careful enough.  These are not marks into the metal; they are scratches in the patina, but under magnification they do detract from the appeal of the coins.

Thanks again.

Ken         
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Mark F
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« Reply #17 on: August 01, 2020, 07:50:25 am »

Ken,

I use sodium sesquicarbonate in a 5% solution with distilled water frequently but not to soften patina but to soak coins at higher risk of bronze disease, per the document below from Texas A&M University Dept of Nautical Archaeology. I've never heard of anyone wanting to make patina softer before cleaning as that would seem to increase the likelihood of damaging the patina during the cleaning process.

Mark

https://nautarch.tamu.edu/CRL/conservationmanual/File12.htm
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