Post by nomad on Dec 20, 2016 14:39:07 GMT
Green and Black Copper Oxide and Specimens.
I have often seen it mentioned that if a specimen is kept free of pests it may last forever, but this is certainly not always the case with some of the older pinned specimens.
Most entomological Continental pins are now made of stainless steel. There is at least one supplier selling English style nickel plated brass pins. Although most use Continental pins and not those small English sorts, if they are selling brass pins, it stands to reason someone is buying them still, at least here and perhaps elsewhere.
Brass when it comes into the contact with insect body fats can cause a chemical reaction that ones started will ultimately destroy the specimen, it may however, take a very long time, perhaps a hundred years or longer or can happen much sooner.
I suspect with the amount of historical English specimens set with brass pins, the chemical reaction does not always happen but when it does it can implode a specimen.
You can tell the specimen has had a chemical reaction, that is caused by body fats coming into contact with brass, because the result is noticeable Green Copper Oxide. In some cases where a certain type of nickel plated brass black pin has been used instead of Green Oxide you get the same condition but it is black. This will cause the same deterioration of the specimen. Specimens that were freshly killed that have a large amount of body fats, irrespective of the specimens size, may be in more danger. In a drawer Green/Black Copper Oxide can spread from one specimen to others and as the specimen is in danger of fragmentation, repining by relaxing is not an option. The Green Copper Oxide usually oozes from the thorax, then down the abdomen, often staining the wings. Sometimes it spiralls upwards like green cotton wool.
A specimen of Frosted Orange, Gortyna flavago set with a brass pin showing Green Copper Oxide. Not yet an especially bad case.
I have often seen it mentioned that if a specimen is kept free of pests it may last forever, but this is certainly not always the case with some of the older pinned specimens.
Most entomological Continental pins are now made of stainless steel. There is at least one supplier selling English style nickel plated brass pins. Although most use Continental pins and not those small English sorts, if they are selling brass pins, it stands to reason someone is buying them still, at least here and perhaps elsewhere.
Brass when it comes into the contact with insect body fats can cause a chemical reaction that ones started will ultimately destroy the specimen, it may however, take a very long time, perhaps a hundred years or longer or can happen much sooner.
I suspect with the amount of historical English specimens set with brass pins, the chemical reaction does not always happen but when it does it can implode a specimen.
You can tell the specimen has had a chemical reaction, that is caused by body fats coming into contact with brass, because the result is noticeable Green Copper Oxide. In some cases where a certain type of nickel plated brass black pin has been used instead of Green Oxide you get the same condition but it is black. This will cause the same deterioration of the specimen. Specimens that were freshly killed that have a large amount of body fats, irrespective of the specimens size, may be in more danger. In a drawer Green/Black Copper Oxide can spread from one specimen to others and as the specimen is in danger of fragmentation, repining by relaxing is not an option. The Green Copper Oxide usually oozes from the thorax, then down the abdomen, often staining the wings. Sometimes it spiralls upwards like green cotton wool.
A specimen of Frosted Orange, Gortyna flavago set with a brass pin showing Green Copper Oxide. Not yet an especially bad case.
