Wood, Coins, & PCGS Boxes - IMPORTANT DATA
magikbilly
Posts: 6,780 ✭
Hi All, thought I would post this here as I feel it is important.
<< <i>CoinAddict - "Peter's (Nichols) response to my question was " The short and easy answer is nothing. I am in the
very fortunate position of having my work tested an examined by the
conservation departments of the leading museums in Europe. They all came
to conclusion that the natural mahogany must be completely untreated to
ensure no interaction with any coins placed in contact with them. In truth
I have renovated many early cabinets from three centuries and some have used
varnish of unknown types on the trays, but then conservation was not a great
issue in Victorian times. My advice, process and sand the tray but
leave them untreated."
In my reply thanking him I invited him to come and check out the forums..
>>
Hi,
from the Art Conservation Center at the University of Denver's Judy Greenfield, Conservator of Objects - "Building a Better Case"
"True African mahogany is reported to be one of the least corrosive woods, but it's expensive and difficult to procure, and other mahoganies sold as substitutes are corrosive" (Hatchfield). Additionally, mahogany is resistant to termite attack. There is disagreement over the benefits of seasoned wood. Kiln-drying (seasoning) wood helps break down and drive off some inherent acids, though it may depress the wood's RH-buffering ability (Miles). But Werner cites the Department of Industry's statement that "[seasoning] wood...accelerates the production of free acetic acid and formic acid. Most of the acid, however, remains in the wood."
So, even if you are lucky and your cabinet is actually made out of true African Mahogany it is still only a lesser evil. While Mahogany is much more stable than red oak, particularly dimensionally which I imagine would play a role in cabinet making, none of this this alters the fact that wood is factually not the best choice of material in which to store coins. I continue to quote from Art Conservation Center at the University of Denver, and this information is specifically in regard to display/storage cases - not so terribly removed from coin storage. And remember, display cases in museums are often temporary and yet these matters are considered. Many of the displayed items cited in the article were metal
"Although some woods are worse than others, all emit a variety of acids, aldehydes and other lignocellulosic degradation products." (Miles). Wood emits mostly acetic acid; formic acid is produced at 1/10th the amount of acetic acid(Blackshaw). Moisture hydrolyzes acetyl groups in the hemicellulose (a form of cellulose, the "building block" of wood) to produce acetic acid. Elevated temperatures appear to foster acetic acid production (Werner)." I don't know what to make of the claims about sanded mahogany - it is also agreed among conservators that all woods must have a barrier between the wood and the display case interior. "No wood can ever be completely sealed to stop emission of organic compounds, though sealants can impede emission." At least one case I saw made by Mr. Nichols appears to have the coins "exposed" to the inside finish, which IMHO should not be inside the case at all. You don't need physical contact for outgassing problems, and we know PCGS slabs are not "sealed" and plastic is gas permeable anyway. Also, the PCGS boxes are "cherry wood finish and are lined with black felt" - I don't have any idea what wood is used, what adhesives, what finish (oil /Varathane?) or what fabric. To me, once closed, the environment in a wood box is concentrated - and the wood just sits there outgassing with the adhesives and finish, waiting to absorb large qualtities of water...now if the box is in a safe.....
Someone mentioned Varathane - "Even after 18 months' drying time, oleoresinous (oil) paints corroded lead in an experiment cited by Miles. As oil products dry, they undergo oxidative degradation which yields volatile organic acids, aldehydes and carbon dioxide (Miles). Oleo-resinous products include oil-modified paints and varnishes, one-component polyurethane varnishes (e.g., Varathane), alkyd paints, epoxy ester paints, aluminum paints, silicone paints and most varnishes (Miles)."
The information just goes on and on...and on - ESPECIALLY about the harmful glues and adhesives that might be used in construction (perhaps more important than the wood and as important as the finish), the fabrics - fabric should not be used where humidity is not controlled (someone mentioned a tarnish retardant cloth - these can be bad - as can certain dyed felts etc.!)...all can be injurious, and usually are unless care is taken. All I am saying is that wood in not an ideal choice, or even second choice for long term coin storage. Yes, this data is about storage/display cases in museums, but most of the problems above seem are mainly influenced by humidity and temperature - variables found in every deposit box and safe. And those are concentrated environments, more than the cases in the above discussion.
Best,
Billy
PS - Despite recent posts to the contrary, oak is indeed the most acidic of woods and does in fact outgas. "The most acidic hardwoods include oak, beech, birch and ash. Oak is the most acidic. With a pH of 3.7 to 4.9, depending on the source (Miles, Stamm), it is capable of liberating up to five percent of its weight in acetic acid (Erhardt)." Brazillian Mahogany, as apparently used by Mr. Nichols, is apparently properly called Honduras Mahogany and IS NOT true African Mahogany and does not share the same "stability" as the African source above - "other mahoganies sold as substitutes are corrosive" (Hatchfield)". I have no idea what wood Mr. Nichols uses other than what he states on his website. As stated above about Mahogany though, regardless of seasoning or kiln drying "most of the acid, however, remains in the wood." I have no issue with Mr. Nichols fine and attractive cases, this is not an attack on his cases nor do I wish to engage in any further discussions about his work as I do not even know him.
<< <i>CoinAddict - "Peter's (Nichols) response to my question was " The short and easy answer is nothing. I am in the
very fortunate position of having my work tested an examined by the
conservation departments of the leading museums in Europe. They all came
to conclusion that the natural mahogany must be completely untreated to
ensure no interaction with any coins placed in contact with them. In truth
I have renovated many early cabinets from three centuries and some have used
varnish of unknown types on the trays, but then conservation was not a great
issue in Victorian times. My advice, process and sand the tray but
leave them untreated."
In my reply thanking him I invited him to come and check out the forums..
>>Hi,
from the Art Conservation Center at the University of Denver's Judy Greenfield, Conservator of Objects - "Building a Better Case"
"True African mahogany is reported to be one of the least corrosive woods, but it's expensive and difficult to procure, and other mahoganies sold as substitutes are corrosive" (Hatchfield). Additionally, mahogany is resistant to termite attack. There is disagreement over the benefits of seasoned wood. Kiln-drying (seasoning) wood helps break down and drive off some inherent acids, though it may depress the wood's RH-buffering ability (Miles). But Werner cites the Department of Industry's statement that "[seasoning] wood...accelerates the production of free acetic acid and formic acid. Most of the acid, however, remains in the wood."
So, even if you are lucky and your cabinet is actually made out of true African Mahogany it is still only a lesser evil. While Mahogany is much more stable than red oak, particularly dimensionally which I imagine would play a role in cabinet making, none of this this alters the fact that wood is factually not the best choice of material in which to store coins. I continue to quote from Art Conservation Center at the University of Denver, and this information is specifically in regard to display/storage cases - not so terribly removed from coin storage. And remember, display cases in museums are often temporary and yet these matters are considered. Many of the displayed items cited in the article were metal
"Although some woods are worse than others, all emit a variety of acids, aldehydes and other lignocellulosic degradation products." (Miles). Wood emits mostly acetic acid; formic acid is produced at 1/10th the amount of acetic acid(Blackshaw). Moisture hydrolyzes acetyl groups in the hemicellulose (a form of cellulose, the "building block" of wood) to produce acetic acid. Elevated temperatures appear to foster acetic acid production (Werner)." I don't know what to make of the claims about sanded mahogany - it is also agreed among conservators that all woods must have a barrier between the wood and the display case interior. "No wood can ever be completely sealed to stop emission of organic compounds, though sealants can impede emission." At least one case I saw made by Mr. Nichols appears to have the coins "exposed" to the inside finish, which IMHO should not be inside the case at all. You don't need physical contact for outgassing problems, and we know PCGS slabs are not "sealed" and plastic is gas permeable anyway. Also, the PCGS boxes are "cherry wood finish and are lined with black felt" - I don't have any idea what wood is used, what adhesives, what finish (oil /Varathane?) or what fabric. To me, once closed, the environment in a wood box is concentrated - and the wood just sits there outgassing with the adhesives and finish, waiting to absorb large qualtities of water...now if the box is in a safe.....
Someone mentioned Varathane - "Even after 18 months' drying time, oleoresinous (oil) paints corroded lead in an experiment cited by Miles. As oil products dry, they undergo oxidative degradation which yields volatile organic acids, aldehydes and carbon dioxide (Miles). Oleo-resinous products include oil-modified paints and varnishes, one-component polyurethane varnishes (e.g., Varathane), alkyd paints, epoxy ester paints, aluminum paints, silicone paints and most varnishes (Miles)."
The information just goes on and on...and on - ESPECIALLY about the harmful glues and adhesives that might be used in construction (perhaps more important than the wood and as important as the finish), the fabrics - fabric should not be used where humidity is not controlled (someone mentioned a tarnish retardant cloth - these can be bad - as can certain dyed felts etc.!)...all can be injurious, and usually are unless care is taken. All I am saying is that wood in not an ideal choice, or even second choice for long term coin storage. Yes, this data is about storage/display cases in museums, but most of the problems above seem are mainly influenced by humidity and temperature - variables found in every deposit box and safe. And those are concentrated environments, more than the cases in the above discussion.
Best,
Billy
PS - Despite recent posts to the contrary, oak is indeed the most acidic of woods and does in fact outgas. "The most acidic hardwoods include oak, beech, birch and ash. Oak is the most acidic. With a pH of 3.7 to 4.9, depending on the source (Miles, Stamm), it is capable of liberating up to five percent of its weight in acetic acid (Erhardt)." Brazillian Mahogany, as apparently used by Mr. Nichols, is apparently properly called Honduras Mahogany and IS NOT true African Mahogany and does not share the same "stability" as the African source above - "other mahoganies sold as substitutes are corrosive" (Hatchfield)". I have no idea what wood Mr. Nichols uses other than what he states on his website. As stated above about Mahogany though, regardless of seasoning or kiln drying "most of the acid, however, remains in the wood." I have no issue with Mr. Nichols fine and attractive cases, this is not an attack on his cases nor do I wish to engage in any further discussions about his work as I do not even know him.
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<< <i>Wow! A lot to digest here. I will do this when I am ready to really analyze this. A lot of juicy information here. Thanks for the post!
This is what makes this site so great! >>
Hi,
and thanks for your nice comments!
Best,
Billy