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Author Topic: Fake patina on this Diadumenian or this Gordian?  (Read 4230 times)

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Offline areich

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Fake patina on this Diadumenian or this Gordian?
« on: April 25, 2009, 02:41:47 pm »
Hi all, I'm not sure about this coin's patina.
In hand it looks convincing but I have little experience with fake patinas
It doesn't smell or taste strange and paint thinner has no noticeable effect.
Maybe I am just suspicious because this lot contained a badly tooled coin and
because I have a similar coin where I'm not sure whether the patina's fake or whether it's just
inexpert smoothing. I'll post it in a reply to this post.

I've left the pictures unedited except for resizing them. Larger pictures are available.

Thanks

Andreas


Andreas Reich

Offline areich

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #1 on: April 25, 2009, 02:44:42 pm »
Here's the Gordian.

Andreas Reich

Offline maridvnvm

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #2 on: April 25, 2009, 02:54:50 pm »
The patina looks as though it was painted on. If I was presented with these images alone I would think the patina to be false.
Regards,
Martin

Offline areich

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #3 on: April 25, 2009, 03:02:22 pm »
That's what I thought (or feared), I used methylated spirit (Brennspiritus)
and nothing happened. Is there something stronger that would remove a fake but not harm a real patina?

When I said 'In hand it looks convincing' I meant the painted on look is not as noticeable but still there.
I wasn't sure if it may have been smothing that caused this look.
Andreas Reich

Offline slokind

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #4 on: April 25, 2009, 05:37:04 pm »
See my specimen, not to brag about but not painted over, on my web page:
https://www.forumancientcoins.com/ayiyoryitika/PontAgrAssets/R22-pros%20DSCN3345.jpg
My reverse R22, double die match to yours.
I always suspect that this kind of over-painting (which looks as if applied from a little bottle, with a fingernail-polish brush, but maybe they just dip it) is applied by sellers (or by the inexpert and uncaring persons who do "conservation" for them) not ONLY to "make it more attractive to buyers" (an insult to the buyers) but also, the coin having been stripped, to cover up anything that might develop bronze disease.  Like red spots; like pitting.
When the latter is the case, it is much harder to arrest BD should it be present.
I never have succeeded in getting this stuff off, either.  Even true patina is not proof against too much sodium sesquicarbonate, but it doesn't touch this black stuff.  Following good professional advice, I have tried acetone.  Old-fashioned paints and varnishes are dissolved by it, but this stuff isn't.
I have a number of such coins, for study, but they make me very unhappy.
Pat L.

Offline bruce61813

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #5 on: April 26, 2009, 10:58:07 pm »
A couple comments,

Pat - sodium sesquicarbonate would not remove varnish or lacquer, it is water soluable, varnish etc is not. You might disolve the copper oxide layer and then the varnish would come off. Some dealers have used a colotin wax, tha tis removed by sodium sesquicarbonate, or even dish washing liquid.

Copper oxide appears in many colors, green, blue, brown and black. Try scanning the coin. Scanners will show black copper oxide as green, apparently it is a 'light' thing and we see it as black, but scanners see it as it's real color.

Lacquer thinner, mineral spirits, turpentine and alcohol will not bother patina, so a little of each on a q-tip would not hurt the coin.

Bruce

PS - it could be painted, but until you try different thinners, you will not know.
too many coins - too little time!!

gavignano

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #6 on: April 27, 2009, 08:19:28 pm »
Boy, it looks painted. Perhaps with black or near black automotive touch up paint.

Offline slokind

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #7 on: April 27, 2009, 11:12:22 pm »
I've been wondering how to express the difference.  I do have coins with real black patina, and, yes, my old HP 6100C scanner lamp did pull out all the green in the black, and besides it's black almost like onyx black.  Not quite.  But the black cover-up, which I suspect on the coins above, is black like lamp-black suspended in something or, as you suggest, like black touch-up paint.  There is no green or any other magical metallic color hiding in it, no matter what kind of a lamp you scan it with.  I very much like the black when it's patina, though it's hard to photograph.  In hand, my best Serdca is practically black, but I have to illuminate and balance it so that it will be legible when posted or printed, and then also the green shows up more.
Here's my newest photo.

• 21 11 06 Æ31 16.92g  axis 6h  SerdicaCaracalla, laureate, head to r.  AVT K M AVRÊ SEVÊ    ANTÔNEINOS.  Rev. Zeus std. l., scepter in his l., holding Victory on orb proffering wreath, to r., facing him.  OVL  PIAS    SERDIKÊS, the epithet interrupted by the Victory.
From Baltimore Show Nov. 2006, bpm; ex Lanz 117, 928,
Still not Varbanov.

I got it at the Baltimore show and stopped to see Doug Smith on my way home (I love to drive).  He photographed it, too.  That's with the greatest professional skill and with his Canon, etc.  His is even greener than mine, yet the coin in hand in ordinary light is almost black.
CLICK FOR 900 PIXELS ACROSS


Offline JRoME

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #8 on: April 28, 2009, 01:15:26 am »
I know you are having a hard time removing it but will that fake patina smear to the touch or is it hard?  I ask because my coin ,in hand, looks very much like areich's Gordian.
I tried throwing some crusties in boiling water for about 10 minutes like I had read on this forum and one of the coins came out looking like a perfect specimen.  It had perfect detail and the nicest patina I had ever seen but when I held it the patina started smearing like clay.  I wish I had a before picture because it was perfect.  Here is what it looks like after I rubbed it with my fingers.

I can't remove it with a brush or pick even though it is pliable.

Offline areich

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #9 on: April 28, 2009, 01:30:08 am »
No, it is hard and smooth. It does not feel, smell or taste supicious
and not looking at it too closely you probably wouldn't notice.
Once you know, it's visible without magnification though.
Andreas Reich

Offline areich

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #10 on: April 28, 2009, 02:47:11 am »
I've had coins like yours among my uncleaneds, when I still bought them.
It may be that the patina itself is so crumbly that it is dissolving and the nice detail with it.
Usually these are coins with a bluish patina but not always.
This is my suggestion anyway from the picture.
Andreas Reich

Offline bruce61813

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #11 on: April 28, 2009, 08:32:09 am »
There are many cases of black clay mixed with green copper carbonte. this forma a hard blck coating that will polish and form a coating that is not easily removed. sometimes soaking or boiling will break up the clay porition and give a duller surface, but if wanted, that can be buffed up, as the copper carbonate will polish. Blue is also a form of copper carbonate generally called Azurite, vs. the green Malachite.

bruce
too many coins - too little time!!

Offline moonmoth

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Re: Fake patina on this Diadumenian or this Gordian?
« Reply #12 on: May 02, 2009, 01:17:41 am »
To remove wax, and occasionally, coats of actual paint, I soak coins for a day in white spirit (Stoddard spirit in the USA) which is sold as a paint-brush cleaner for oil-based paints.  Then, soap and water and a nylon brush to clean them up.  Some painted coins might need more than one soak.

It still amazes me that anyone would just paint a coin .. I have seen silver and brown paints .. but there it is.  As far as I know, white spirit does not affect any genuine patina, because patinas are not oil- or hydrocarbon-based.

Bill
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