[4] Deprived of water, the reaction cannot continue. Posted at Dec 14/2007 10:10PM:
H��S�n�0����Y�L�G�D��XT%U7l���1������I�!�#;��=�k��S
2�A��`O˹� by Evie. [2][4], "Archaeologies of the Greek Past: Bronze disease", Journal of the American Institute for Conservation, "The Critical RH for the Appearance of “Bronze Disease” in Chloride Contaminated Copper and Copper Alloy Artefacts", "Bronze Disease: A Review of Some Chemical Problems and the Role of Relative Humidity", https://en.wikipedia.org/w/index.php?title=Bronze_disease&oldid=980733656, Conservation and restoration of cultural heritage, Creative Commons Attribution-ShareAlike License, This page was last edited on 28 September 2020, at 04:00. (5) Cu+ + Cl− → CuCl, The reaction then repeats from equation (3). d��;�����R����sG�1$�7�1҈"����C7��a���~�Gge%��)!7\ WG_1����n�Y����rze���f�}@:;xL���U���Z�UYpӥi��Y��)�q-�����qp�د-�=�])aא�����+,7��s��?&��)~?>�
endstream
endobj
9 0 obj
436
endobj
4 0 obj
<<
/CropBox [ 36 36 756 576 ]
/Type /Page
/Parent 5 0 R
/Resources <<
/Font <<
/F0 6 0 R
>>
/ProcSet 2 0 R
>>
/Contents 8 0 R
>>
endobj
17 0 obj
<<
/Length 18 0 R
/Filter /FlateDecode
>>
stream
Well, no man-made artifacts can last forever... thanks for new info!. It is the presence of two different white and green salts that lead to the fuzzy green appearance. Kuy Yeon Lee: I always get confused about the fact that the buildings and sculptures that look green today were actually...bronze color. It manifests itself as either a powdery green substance on the surface of the metal or as a warty or waxy film over the surface of an artifact. ��Κ��9����H6퉸��ƞ�����o=q�[Y���B�zy���
H� If not treated, complete destructio… The oxide may coat the artefact with unsightly but harmless black spots or generally, darken the metal.
'�ס�~zl������CW�0���ۮY��K�4�]��ؾzT��qOӅ�����s�U,����g{u#!��!�yվ Ŧ�iBa����.J����!x|v#��n�%�M���9 It leaves the surface with patches of pale green, powdery material. ♦Bronze “disease” is a condition in which the coin produces acid (normally hydrochloric or hydrosulfuric acid) internally, and begins to disintegrate ♦The exterior usually exhibits green or brown “growths” that cover the pitting that acids will create Once treated, the specimen should be held in a dry environment and periodically inspected for recurrence of bronze disease as no long-term treatment has been confirmed.[2][3]. [2][3], Soaking in sodium carbonate—which does not form a complex ion with copper and is unlikely to affect the patina but is slower than the sesquicarbonate—or benzotriazole (highly carcinogenic) aqueous solutions may also be used. Harry Anastopulos: Somehow I figured you'd pick this one, Evie. Fax: (401) 863-9423
Providence, RI 02912
Instead of rinses, electrolysis may be used, often with sodium carbonate as the electrolyte and mild or stainless steel as the anode.
Wipe surfaces gently, and do not spray or immerse your hardware in the disinfectant. It is not a bacterialinfection, but the result of a chemical reaction with the chlorides that usually occurs due to contamination of the bronze object by saltwater or from burial in specific types of soil where chloride salts are present. It can occur as both a dark green coating, or as a much lighter whitish fuzzy or furry green coating. This is what can happen in just a few weeks! �f���ų��9�Q ;�F���/r٬��iQ{)p�C,t����\���ƛ?�v��S�SN���W��s �d�C�r(�{�\�k?���/�������·nH8�x�
endstream
endobj
18 0 obj
455
endobj
10 0 obj
<<
/CropBox [ 36 36 756 576 ]
/Type /Page
/Parent 5 0 R
/Resources <<
/Font <<
/F0 6 0 R
/F1 11 0 R
/F2 13 0 R
/F3 15 0 R
>>
/ProcSet 2 0 R
>>
/Contents 17 0 R
>>
endobj
20 0 obj
<<
/Length 21 0 R
/Filter /FlateDecode
>>
stream
[2][3], Use of tap water for initial carbonate rinses is fine as any chloride content in the water is low compared to the content found when the chlorides from the contaminated artefact have dissolved into the water. The sesquicarbonate may remove copper from the artefact as it forms a complex ion with copper. Posted at Dec 11/2007 08:49PM:
This certainly highlights how easily artifacts of the past can disappear and also how important what remains we do find are! However, re-exposure of the object to even atmospheric water can restart the process. This is visible as a blackening or darkening of the copper surface. One of the most effective ways to turn a character's hair completely white would be the stress of prolonged illness.There may be some Truth in Television to this, but typically it's taken to extremes.