Cotton gloves

Susan Stock <susans [at] rom__on__ca> writes

>Paul Green <p.r.green [at] leeds__ac__uk> writes
>
>>A colleague of mine recently visited the States and was given some
>>lint-free cotton gloves with finger grips to handle manuscript
>>material. He found these much better than ordinary lint-free cotton
>>gloves or latex rubber gloves. ...
>
>Has anyone analyzed the composition of the 'grips'? Many years ago,
>I found that 'grip marks' were left on silver, indicating the
>presence of sulphur in the grip material. ...

And David Harvey <top10denverdave [at] aol__com> writes:

>>I too have observed problems with cotton gloves with the griping "dots".
They leave significant corrosion patterns on metals (especially silver
objects) and leave readily observable residue patterns on glass, ceramics,
polished wood, and gilt objects. One manufacturer identifies the material
in the dots as a "rubber compound". <<

>I too have observed problems with cotton gloves with the griping
>"dots". They leave significant corrosion patterns on metals
>(especially silver objects) and leave readily observable residue
>patterns on glass, ceramics, polished wood, and gilt objects. One
>manufacturer identifies the material in the dots as a "rubber
>compound". ...

During a recent IR spectroscopic analysis site visit I was handling
glass microscope slides with gloves having knobby fingergrips and I
noticed the creation of a spotted pattern on the glass.  I pressed
one of these nodules against the ATR crystal of my TravelIR
spectrometer and obtained a spectrum of phthalate plasticized
poly(vinyl chloride).  When I removed the glove from the crystal a
residue was left which produced a spectrum of phthalate plasticizer.
As a result of recent notices on the Conservation DistList I decided
to repeat the analysis for confirmation.  I obtained three gloves of
this type from staff at CCI.  These three gloves look identical to
each other and had been previous used.  Unfortunately their
containers have been lost and their source is unknown.  They are
made of four separate pieces of fabric--two pieces with nodules, two
without.  The palm and palm side of four fingers are made from one
piece of knobby fabric and the palm side of the thumb from a second.
The back of the hand is made of a single piece of fabric without
nodules and the back of the thumb is made from another piece of the
same fabric.  There are three gathers about 2.5 inches long along
the top of the knuckles parallel to the fingers.  One glove has a
label bearing the inscription--"84%Cotton 16%PVC Made in China
RN#65739".

Nodules of all three were analyzed as described above and have the
same composition.  The nodules are made of phthalate plasticized
poly(vinyl chloride).  All leave a residue of dioctyl phthalate on
the ATR crystal after being pressed against it.  In some cases the
residue also seems to contain particles of plasticized poly(vinyl
chloride), presumably fragments of the nodules that have broken off
and deposited on the crystal.

Stock suggests that grip marks on silver indicate the presence of
sulfur. This may be true if the nodules are made of something that
contains sulfur, such as sulfur vulcanized rubber, perhaps the
"rubber compound" cited by Harvey.  However, in the case of the
gloves I analyzed, sulfur tarnishing is unlikely.  A much more
likely scenario is corrosion by acidic products from hydrolysis of
the phthalate ester plasticizer (perhaps catalyzed by the metal).
Yvonne Shashoua described the production of phthalic acid from
hydrolysis of phthalate plasticizers in her PhD thesis entitled
"Inhibiting the deterioration of plasticized poly(vinyl chloride)",
pp 36-37.

Whether a product is likely to transfer material to an object can be
assessed by using the technique of pressing the product against a
freshly cleaned microscope slide or polished metal surface (or any
other polished surface of interest) then observing the polished
surface by holding it so that the specular reflection from a broad
light source such as a window can be seen.  If material is
transferred it will be revealed by imperfections in the reflection.
This will show transfer by simple contact.  A different test where
the product is dragged across the polished surface will show if
material can be transferred by rubbing, which might happen with soft
materials, such as the nodules on the gloves.  Neither test shows if
material can be transferred to rough surfaces by abrasion.

R. Scott Williams
Senior Conservation Scientist (Chemist)
Conservation Processes and Materials Research
Canadian Conservation Institute
613-998-3721
Fax: 613-998-4721


                                  ***
                  Conservation DistList Instance 16:10
                 Distributed: Wednesday, July 31, 2002
                       Message Id: cdl-16-10-003
                                  ***