Author Topic: One of the severe cases  (Read 374 times)

0 Members and 1 Guest are viewing this topic.

Offline Pellinore

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 801
    • Some numismatic books for sale on our website
One of the severe cases
« on: August 27, 2017, 02:39:30 AM »
I'm busy cleaning some coins. I'm putting the coins in the soda solution in glass or plastic bottles and put them on the highest window sill, where they can get quite warm in the afternoon. I'm changing the liquid when it gets blue, usually applying a light scrub.

This follis of the emperor Phokas was even dark when I bought it three years ago, but last year it flamed out blue-green. It was in the solution for over a year, and although it's still covered in green bumps, I feel it might be stable now: nothing has changed in a long time. Can I take it out and preserve it in isolation safely? How do you keep your formerly afflicted coins?

-- Paul
 

Offline bruce61813

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 662
    • Gringgotts Coins
Re: One of the severe cases
« Reply #1 on: August 27, 2017, 03:53:54 AM »
Give this a brushing under running water, then put back into a soda soak. There is hope yet. Under extreme cases, use a sewing needle and magnifier to pick away some of the really bad areas, to open the deep areas to the solution. Heating the coin in the soda solution to the boiling point, then allow it to cool and soak also helps. Boiling forces air, trapped in small spaces, to expand and as the solution cools it will be drawn into the crevices.


Bruce

Offline Pellinore

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 801
    • Some numismatic books for sale on our website
Re: One of the severe cases
« Reply #2 on: September 02, 2017, 01:08:38 PM »
Thanks for giving me new courage. I'll keep you all posted.
-- Paul

Offline Pellinore

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 801
    • Some numismatic books for sale on our website
Re: One of the severe cases
« Reply #3 on: October 09, 2017, 09:05:58 AM »
I have taken it out of its batch some weeks ago. Still the hard green bumps are looking stable, nothing much has happened to the coin in the last few months. But it's not an attractive coin anymore, as it was when I bought it.
-- Paul

Offline EWC

  • Meritorious Member
  • ****
  • Posts: 601
Re: One of the severe cases
« Reply #4 on: October 09, 2017, 12:02:26 PM »
When I was young the standard text on coin cleaning etc, in the UK, was well known:

"The Conservation of Antiquities and Works of Art: Treatment, Repair and Restoration" by Harold James Plenderleith,

see for background

https://hyper-db.de/monopedia/wiki/index.php?title=Harold_Plenderleith

Has anyone here read it?  Or even heard of it?

Just curious

Rob T


Offline Figleaf

  • Administrator
  • Honorary Member
  • *****
  • Posts: 25 515
Re: One of the severe cases
« Reply #5 on: October 12, 2017, 09:16:37 AM »
Keep on trying, Pellinore! They may not be in the same condition when you are through, but they will still have their great historical interest. Besides, the experience you are gaining is worthwhile.

@EWC: In my formative years, I used Horst Winskowsky's Münzen pflegen, which had the advantage of being in German, close enough to Dutch for a youngster. I see the book is still traded on the internet. I don't think I ever saw Plenderleith's book offered.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline EWC

  • Meritorious Member
  • ****
  • Posts: 601
Re: One of the severe cases
« Reply #6 on: October 12, 2017, 10:19:26 AM »
as per Plendereith I used lab grade Sodium Sesquicarbonate for about 40 years.

But I am quite off the wavelength of what is being done here

I do not know if the mix applied here works

But, at a guess, the green now on the coin looks most probably like a stable but unsightly encrustation to me

Rob T

Offline Pellinore

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 801
    • Some numismatic books for sale on our website
Re: One of the severe cases
« Reply #7 on: October 12, 2017, 09:38:21 PM »
Well, it was a very attractive nice dark coin at first, that I bought on a reputable auction in Germany in December, 2014. In the course of 2016 it turned out to be very green with BD, then I started treating it in the sodium-sodium bicarbonate solution. The green fuzz disappeared, but a number of green encrustations stayed on. They look like they are never going away. But they were not there in 2014.
Pity, for I largely lost my taste for Byzantine coins because of this.
-- Paul

Offline EWC

  • Meritorious Member
  • ****
  • Posts: 601
Re: One of the severe cases
« Reply #8 on: October 13, 2017, 08:50:56 AM »
But they were not there in 2014.

Thanks - confirms what I guessed. 

Rob T

Offline Pellinore

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 801
    • Some numismatic books for sale on our website
Re: One of the severe cases
« Reply #9 on: October 13, 2017, 09:52:58 AM »
I used the mix on a dozen other coins, where it worked alright. The reputable auction house, by the way, was Gitbud & Naumann.
-- Paul

Offline EWC

  • Meritorious Member
  • ****
  • Posts: 601
Re: One of the severe cases
« Reply #10 on: October 13, 2017, 10:31:01 AM »
I used the mix on a dozen other coins, where it worked alright. The reputable auction house, by the way, was Gitbud & Naumann.

Coins are ornary beasts, and do not always do what they are told.  Problem will likely be that the coin was acid or alkali cleaned and then repatinated without well washing first.  An auctioneer could not know this would happen. A reputable dealer ought to refund in these circumstances if the coin went back "as is"   

Now - it seems a new and uneven patination/encrustation is building up.   

Rob T

Offline Pellinore

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 801
    • Some numismatic books for sale on our website
Re: One of the severe cases
« Reply #11 on: October 13, 2017, 03:09:23 PM »
See here for some dramatic footage of two other victims.
-- Paul

Offline bruce61813

  • Moderator
  • Meritorious Member
  • *****
  • Posts: 662
    • Gringgotts Coins
Re: One of the severe cases
« Reply #12 on: October 28, 2017, 03:52:23 PM »
If you can find this article:   JAIC 1994, Volume 33, Number 2, Article 6 (pp. 141 to 152)   
 
A PERSPECTIVE ON THE HISTORY OF THE CONSERVATION OF ARCHAEOLOGICAL COPPER ALLOYS IN THE UNITED STATES
TERRY DRAYMAN-WEISSER

It explains a lot and is worth the time to read. The soda/soda mix is a homemade version of Sodium Sesquicarbonate, but easier to deal with in small amounts. 

Bruce
 
« Last Edit: October 28, 2017, 04:07:24 PM by bruce61813 »