Hi,
In response to the original query - gold in the most noble of metals
and essentially pure gold will not oxidize nor corrode. But very few
objects are made from pure gold. The gold is usually alloyed with a
small percentage of copper, silver and there can be other alloys
invovled as well. There are numerous methods of gilding metal surfaces
beyond the use of water, oil, or amalgam. Particularly in
pre-columbian artefacts made from the tumbaga alloy a technique known
as depeltion gilding was employed in which the object was subjected to
a bath of uric acid that depleted the surface and left a thin
monolayer of gold behind.
So there are consituents in the composition of most gold objects that
given enough moisture, pollutants, and acids, will react (especially
the copper in the alloy).
I agree with Marc that it is probably a good idea at this point to
forego the use of wood if you are replacing the storage units. My
preference would be for anodized aluminum. It is lightweight yet
strong, and inert. When I was at Colonial Williamsburg we put all of
the new metals and objects storage into compact shelving units made
from anodized aluminum - custom made by Crystallizations. I think that
both the conservators and the curators are still delighted with that
choice.
Cheers!
Dave
David Harvey
Conservator
Los Angeles, California
On 6/22/07, Marc A Williams <[log in to unmask]> wrote:
>
>
> In the US, many wooden storage structures are made of clear poplar sealed
> with a waterborn sealer. Poplar is a stable wood and not acidic. Exhibit
> cases
> are often sealed with a product called Marvl Seal or are faced with Formica
> (tm), also a stable product.
>
> A couple of comments on this post. In the US, poplar is an ambiguous term.
> Cottonwood (common name) is of the species Populus. However, the common
> name poplar usually refers to yellow poplar (correct common name, also
> sometimes called tulip poplar), which is the species liriodendron
> tulipifera. Cottonwood and yellow poplar are not the same or related woods,
> so clarification would be helpful.
>
> Second, most woods are acidic, but it is not just the acidity that causes
> corrosion or other degradative processes to objects inside wooden
> enclosures. The following research excerpt specifically found that pH
> (acidity) was NOT correlated with corrosion. [MEASURING THE RATE OF
> ATMOSPHERIC CORROSION IN MICROCLIMATES, by HARALD BERNDT: JAIC, 1990, Volume
> 29, No. 2, pp. 207-220] "Corrosiveness of atmospheres in the vicinity of
> wood products varies significantly with the type of wood product but is not
> correlated with the pH of the wood product. In the worst case, corrosion was
> accelerated by a factor of 46, compared to the average corrosiveness of the
> laboratory air under test conditions. The least offensive material
> accelerated corrosion by a factor of 11. Corrosiveness seems to increase
> slightly with the time between sample preparation (milling) and the
> corrosion test. Treatment and storage effects on corrosiveness need further
> systematic investigation." While this study was done specifically with
> museums in mind, it did not test all possible types of wood products.
>
> I have not been following the wood-as-storage-material debate (other than
> generally advising against it for sensitive materials), so I don't know if
> additional research has been done. But it seems to me that wood is not a
> good idea for a new purchase, particularly with the easy availability of
> powder-coated metal enclosures, or if the budget is adequate, even stainless
> steel. The enclosures do not have to be made specifically for museums, as
> most manufacturers (at least in the US) have moved away from solvent-based
> paints to powder coat paints for environmental reasons. I'd love to hear
> other opinions out there!
>
> Marc
>
> American Conservation Consortium, Ltd.
> 4 Rockville Road
> Broad Brook, CT 06016
> www.conservator.com
> 860-386-6058
>
> *Collections Preservation Consultation
> *Conservation Assessments & Surveys
> *Low-Tech Environmental Control
> *Moisture Management Solutions
> *Collections in Historic Structures
> *Collections Care Grant Preparation
> *Conservation Treatment of:
> Furniture
> Painted Wood
> Horse-Drawn Vehicles
> Architectural Interiors
>
> Marc A. Williams, President
> MS in Art Conservation, Winterthur Museum Program
> Former Chief Wooden Object Conservator, Smithsonian Institution
> Fellow, American Institute for Conservation (AIC)
>
>
> ----- Original Message -----
> From: "Diane Gutenkauf" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, June 22, 2007 9:59 AM
> Subject: Re: [MUSEUM-L] Replace plywood
>
> Any materials considered safe for use in exhibit cases is also appropriate
> for
> storage environments. Start with the National Park Serivce (USA) web site:
>
> The Exhibit Conservation cd-rom
> http://www.nps.gov/hfc/products/cons/ex-con-guidelines.htm
>
> In the US, many wooden storage structures are made of clear poplar sealed
> with a waterborn sealer. Poplar is a stable wood and not acidic. Exhibit
> cases
> are often sealed with a product called Marvl Seal or are faced with Formica
> (tm), also a stable product.
>
> Best of luck
>
> Diane Gutenkauf
> Director
> Robert R. McCormick Museum
> [log in to unmask]
>
> On Thu, 21 Jun 2007 17:20:12 -0700, Oscar Gaona <[log in to unmask]>
> wrote:
>
> >I'm forwarding this message from two colleagues:
> > ------------
> > Receive a cordial greeting from the conservation team of the Gold Museum
> of Colombia, South America.
> >
> >In this moment our museum remodels its installations, inside the current
> process of transformation, the Museum is interested in renovating the wooden
> drawers (made of plywood) that during more than 20 years have been used to
> storage the gold work collection.
> >
> >To carry out this change, we have begun investigating on conservation
> materials. Until the moment we have not resolved the problem of which
> material should be used to replace the plywood but we are making trays with
> sheets of expanded polyethylene (Jumbolon or Ethafoam), with the form in
> negative of each object that help to organize and protect theme inside this
> boxes. Each box can contain up to three of these trays.
> >
> >In spite of the fact that the plywoods are not advisable for the
> conservation, until now, our gold work objects have not suffered any type of
> chemical or biological deterioration. The wooden drawers have been extremely
> resistant but, in the face of their potential chemical instability, we want
> to
> study other possibilities. For such a reason we are interested in knowing
> your
> experiences, suggestions, recommendations or new contacts.
> >
> >We thank your collaboration,
> >PABLO OBANDO and ANGELA OVALLE
> >Restorers of Cultural Heritage
> >Conservation Team
> >Gold Museum of Colombia
> >
> >------------
> >
> > Regards,
> > Oscar
> >
>
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