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Controlling humidity & tarnishing in showcases


#1

In my never-ending efforts to combat silver tarnish, I’m wondering
if reducing the amount of moisture in the showcases would also reduce
the rate that the jewelry tarnishes while on display?

A company called ULINE (phone # 800-295-5510) sells various sized
bags of desiccant, calcium chloride, and silica gel (page 249 of
their catalog) at seemingly very reasonable prices. However, I don’t
know which product would be best (desiccant, calcium chloride, or
silica gel?) and I don’t know if any of these products gives off any
other gases that would be even more harmful & negatively affect the
silver.

Doug


#2

G’day

sells various sized bags of desiccant, calcium chloride, and silica
gel (page 249 of their catalog) at seemingly very reasonable
prices. However, I don't know which product would be best
(desiccant, calcium chloride, o silica gel?) and I don't know if
any of these products gives off any other gases that would be even
more harmful 

First lets clear things up a bit; A dessicant is any substance which
absorbs water to provide a dry atmosphere.

Anhydrous calcium chloride is an excellent dessicant, but it is also
deliquescent which means not only does it absorb water from the
atmosphere, but to the extent that it will actually dissolve in what
it absorbs, leaving a rather sticky and corrosive mess. The best for
you would be silica gel which is non toxic, gives of no gases, and is
a good dessicant. Buy only the silica gel which contains a moisture
indicator. When it is blue it is dry and ready to use; when pink it
is damp and needs to be heated to drive out the moisture to return it
to blue and be ready to use again. It can be recycled many times in a
microwave oven. Spread it on a plate and microwave on a low setting
until it attains a deep blue colour again. For the curious, the gel
contains cobalt chloride as the moisture indicator.

I have used silica gel many times in a Mason jar to dry watches
which have had a bit of a bath; with no ill effects.

Cheers for now,
John Burgess;
@John_Burgess2 of Mapua, Nelson NZ


#3

Doug,

I save every bag of Silica Gel I get in any item I buy, like shoes
and bags to name a few, which generally have one or two little
pouches inside. They are tiny and I could swear it helps. I use the
tiny bags in the boxes where I keep my Sterling wire. I really think
it helps.

You can also get the silica in 5 gal buckets from Lowe’s or Home
Depot. They had it last Summer, I’m not sure about now. We were
considering buying some of those for our moist basement but opted for
a machine instead.

Hope this helps!

Vera
Vera Battemarco


#4

Silica gel is used in the museum field due to it ability to be "set"
at a particular humidity by putting it in a fixed environment. Or, if
you just want it “dry” you can dry (and redry when necessary) by
placing it in a baking pan in an oven at a low temp. It is also
considered inert so it will not offgass any damaging chemicals…


#5
In my never-ending efforts to combat silver tarnish, I'm wondering
if reducing the amount of moisture in the showcases would also
reduce the rate that the jewelry tarnishes while on display? 

In my store, we discovered that the formaldehyde and perhaps other
chemicals used as glues in the showcases and displays, pads, etc.,
actually break down under the showcase lights and release small
amounts of sulfur dioxide…which blackens silver quickly. Just
like keeping your silver in a broen paper bag. Many of the products
used in manufacturing will darken silver.

Yipes.

Wayne


#6

Hello people,

I’m no expert on any of this stuff (he said modestly) but I’m
shameless when it comes to kvelling about children and grandchildren.

My daughter is an objects conservator for an east coast art museum in
the US and has worked hither and thither in that field, tending to
specialize in metals and stone. Her museum mounted a major exhibition
of early American silver in a museum in Nagoya, Japan a few years
ago. The showcases were designed with all the cutting edge technology
you can possibly imagine; atmosphere carefully controlled, gadgets to
monitor, modify, and record moisture, temperature etc. Megabucks were
spent on avoiding tarnish problems and yet in a very short time the
teapots and platters in the cases were turning black. She flew back
to Japan to discover that all instructions and specs had been
followed by the host museum who built the cases, but they chose the
paint for inside the cases. Right colour, wrong formulation. That
paint apparently outgassed some fumes which damaged the silver. Maybe
many of you know about this sort of thing but I didn’t. If anyone is
interested in pursuing that bit of knowledge further - I could
probably find out from her what sort of paint or what chemical in it
caused the damage. Imagine what a disaster if one of you retailers
happened to paint your whole store with that paint!

Write me offline if there is any interest and I’ll see if I can get
her report on that adventure.

Marty Hykin in Victoria @Olwyn


#7

Hello All,

I had some responses to my recent post regarding this problem and so
gathered some more detail from my daughter.

The story - My daughter, an objects conservator, had sent a large
exhibit of priceless early American silver to a museum in Japan
where the display cases which were provided for the objects were
made by the museum there and did not follow the required specs and
guidelines. The result was that the entire collection was turned
black in less than three months - Great consternation and beaucoup
de work to get it restored.

My memory of her description was close, but not bang on the money.
Following my comments is my daughter’s recollection of the situation
which, as you will see, mentions a number of possible causes as well
as the paint. When I last had spoken with her about this event, she
and her staff were right in the middle of the unfolding catastrophe
and thought the problem was the paint on, or in, the cases. At that
point they perhaps had not seen all the other screw-ups that may
have been, individually or in combination, the cause of the
blackened silver.

Also, following, you will see the guidelines for silver display used
at the Boston Museum of Fine Arts for silver display. These may not
be practically applicable to retail jewelry shops where objects must
be more readily accessible than in museums where security is a
higher concern and where there is very little need to handle the
objects on exhibit.

With regard to the “PVC paint” she mentions in her description -
there are several possibillities and I’m not clear which applies.

First - there is vinyl paint, paint containg PVC’s as we know them,
polyvinlylchlorides.

Second - there is paint designed to paint onto PVC plastics - This
paint contains lots of very volatile solvents and outgasses like
crazy, a likely candidate.

Third _ “PVC” is abbreviation for “Pigment Volume Concentration” in
the paint industry and depending on that value in a given paint, may
require addition of extra binders etc which in themselves might
cause problems.

In any case, the museum display case guidleines below will give you
a good idea of what to watch for - Basically stay away from paints
and all smelly organics if you can.

I hope this is helpful or satisfies your curiousity.

Marty Hykin, Victoria BC.


#8

Hi Gang,

In the March issue of AJM there’s a description of a new product
from Rio Grande called ‘Silver-Guard’.

It’s purpose in life is to reduce or eliminate silver tarnish in
display cases. The description lists it as a 2" W x 1" D x 3/8" H
block. Each block is designed to protect a case of 10 cubic ft. for 3

  • 6 months.

If you’re going to the MJSA Expo in NYC in Mar., you’ll be able to
see it at the Rio Grande booth.

Usual disclaimers, just a very satisfied Rio Grande customer.

Dave