squirrel Posted May 26, 2007 Report Share Posted May 26, 2007 picked this one up a while back. obviously had issues during striking. anybody think i can get this slabbed? The "patina" is also quite odd. it resembles rust in color and texture. very even, not like corrossion or verdigris. Link to comment Share on other sites More sharing options...
gxseries Posted May 26, 2007 Report Share Posted May 26, 2007 I think that is the very reason why overstrikings in 1797 didn't use previous year dies except 1793 - dies must have been rusty or kept inproperly Link to comment Share on other sites More sharing options...
rittenhouse Posted June 4, 2007 Report Share Posted June 4, 2007 picked this one up a while back. obviously had issues during striking. The "patina" is also quite odd. it resembles rust in color and texture. very even, not like corrossion or verdigris. The "patina" is cuprous oxide, aka "copper rust" or "red plague" (see wiki). It is considered corrosion. Forms by galvanic corrosion, humidity, ammonia, etc. Nasty strike w/ obvious poorly made planchet. The deep indent in the center looks like a strike-thru (but could be post-strike damage). Very cool. I like it. Link to comment Share on other sites More sharing options...
squirrel Posted June 4, 2007 Author Report Share Posted June 4, 2007 The "patina" is cuprous oxide, aka "copper rust" or "red plague" (see wiki). It is considered corrosion. Forms by galvanic corrosion, humidity, ammonia, etc. Nasty strike w/ obvious poorly made planchet. The deep indent in the center looks like a strike-thru (but could be post-strike damage). Very cool. I like it. thanks for the info! ive never heard of copper rust! did you see the image of the edge before i deleted it? ill re-upload if you didnt. the edge is a sharp bevel, and the whole coin looks like a flying saucer from edge on Link to comment Share on other sites More sharing options...
rittenhouse Posted June 4, 2007 Report Share Posted June 4, 2007 thanks for the info! ive never heard of copper rust! did you see the image of the edge before i deleted it?ill re-upload if you didnt. the edge is a sharp bevel, and the whole coin looks like a flying saucer from edge on Didn't see the edge photo but I can see the bevel from the current photos. Really poorly formed planchet w/ a poor strike. Link to comment Share on other sites More sharing options...
RW Julian Posted June 4, 2007 Report Share Posted June 4, 2007 picked this one up a while back. obviously had issues during striking. anybody think i can get this slabbed? The "patina" is also quite odd. it resembles rust in color and texture. very even, not like corrossion or verdigris. About 12 years ago I went through an accumulation of 5 kopeck pieces (several thousand pieces) mostly of the 1770s through 1790s. These had been kept together more or less sealed up for several decades and most were covered with a fine copper oxide. The oxide was so heavy in some case that a cloth had to be used to see details of the coin. RWJ Link to comment Share on other sites More sharing options...
squirrel Posted June 4, 2007 Author Report Share Posted June 4, 2007 About 12 years ago I went through an accumulation of 5 kopeck pieces (several thousand pieces) mostly of the 1770s through 1790s. These had been kept together more or less sealed up for several decades and most were covered with a fine copper oxide. The oxide was so heavy in some case that a cloth had to be used to see details of the coin. RWJ wow! that must have been fun! so, like a pirates treasure chest full of copper!? any keepers? (or photos?) ill bet there was a good story there! Link to comment Share on other sites More sharing options...
RW Julian Posted June 4, 2007 Report Share Posted June 4, 2007 wow! that must have been fun! so, like a pirates treasure chest full of copper!? any keepers? (or photos?) ill bet there was a good story there! You are right, it was a pleasant experience. Most of the pieces laid aside were interesting varieties, such as overdates. I did, however, find a Brekke 238, the scarce 1779 piatak using the earlier eagle. Also purchased from this hoard were several EM pieces from the early 1780s in which the mint was experimenting with planchet size. RWJ Link to comment Share on other sites More sharing options...
gxseries Posted June 5, 2007 Report Share Posted June 5, 2007 Would there happened to be any of those scarce TM coins in those lots? Link to comment Share on other sites More sharing options...
grivna1726 Posted June 5, 2007 Report Share Posted June 5, 2007 The "patina" is cuprous oxide, aka "copper rust" or "red plague" (see wiki). It is considered corrosion. Forms by galvanic corrosion, humidity, ammonia, etc. I also was unfamiliar with the term "red plague". http://en.wikipedia.org/wiki/Red_plague_%28corrosion%29 says: Red plague is an accelerated corrosion of copper when plated with silver. After storage or use in high-humidity environment, cuprous oxide forms on the surface of the parts. The corrosion is identifiable by presence of patches of brown-red powder deposit on the exposed copper. Red plague is caused by normally occurring electrochemical potential between the copper and silver, leading to galvanic corrosion occurring in pits or breaks in the silver plating. It develops in the presence of moisture and oxygen when the porosity of the silver layer allows them to come in contact with the copper-silver interface. It is an electrochemical corrosion - a copper-silver galvanic cell forms and the copper acts as sacrificial anode. In suitable conditions, the corrosion can proceed rather quickly and lead to total circuit failure. There appear to be visible traces of silver plating around the eagle, possibly from use as jewelry. Does the coin show marks suggestive of having been looped or mounted in a bezel? (Although something so heavy seems impractical for wearing as a pendant or a brooch.) Link to comment Share on other sites More sharing options...
rittenhouse Posted June 5, 2007 Report Share Posted June 5, 2007 I also was unfamiliar with the term "red plague". http://en.wikipedia.org/wiki/Red_plague_%28corrosion%29 says: Red plague is an accelerated corrosion of copper when plated with silver. After storage or use in high-humidity environment, cuprous oxide forms on the surface of the parts. The corrosion is identifiable by presence of patches of brown-red powder deposit on the exposed copper. Red plague is caused by normally occurring electrochemical potential between the copper and silver, leading to galvanic corrosion occurring in pits or breaks in the silver plating. It develops in the presence of moisture and oxygen when the porosity of the silver layer allows them to come in contact with the copper-silver interface. It is an electrochemical corrosion - a copper-silver galvanic cell forms and the copper acts as sacrificial anode. In suitable conditions, the corrosion can proceed rather quickly and lead to total circuit failure. There appear to be visible traces of silver plating around the eagle, possibly from use as jewelry. Does the coin show marks suggestive of having been looped or mounted in a bezel? (Although something so heavy seems impractical for wearing as a pendant or a brooch.) That is merely ONE means by which copper rust forms. Do not mistake that it is the only one. Link to comment Share on other sites More sharing options...
RW Julian Posted June 5, 2007 Report Share Posted June 5, 2007 Would there happened to be any of those scarce TM coins in those lots? Unfortunately, no. RWJ Link to comment Share on other sites More sharing options...
grivna1726 Posted June 5, 2007 Report Share Posted June 5, 2007 That is merely ONE means by which copper rust forms. Do not mistake that it is the only one. Okay, thank you. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.