Wednesday, November 10, 2010

Button, Button

From the desk of Colleen Wilson,
Conservator at the Royal BC Museum

Sometimes artifacts are difficult to exhibit because their appearance is incomplete. A typewriter without a ribbon? A telephone without a dial? It’s important that our displays are accurate.

Brown silk bodice.

As part of a coming exhibition, we’re preparing a bodice and skirt from c.1889. It’s simple but dressy, made of “shot” silk; the vertical warps are chestnut brown and the horizontal wefts, dark brown, giving a shimmery, if somewhat sombre, effect. Unfortunately, at some point all the buttons were removed and as there were sixteen of them down the centre front, their appearance is critical.

Emily Carr, wearing a similar bodice, pictured with her brother Dick c.1889.
BC Archives #I-60892

We have cards of buttons from the same period that look appropriate, but we wanted to ensure that the button material would not harm the fabric of the bodice. The earliest plastics were developed in the late 19th Century; the inventors were not always concerned about long term stability.

A card of buttons.

Fortunately Dr. JoAnn Peters is spending her sabbatical from the Chemistry Department of the University of Central Washington with us, researching methods for identifying plastics in the RBCM collections. The buttons appear to be compression moulded from a plastic material; in the late 1800s this could have been cellulose nitrate (celluloid), gutta percha, shellac, or vulcanized rubber.

Dr JoAnn Peters at the microscope.

Dr. Peters took samples by rubbing the edge of one of the buttons on the frosted end of a microscope slide, leaving a very slight residue on the slide and no visible evidence on the button. She tested for cellulose nitrate (diphenylamine test) and sulfhydryl groups (azide test). The results eliminated cellulose nitrate (which breaks down releasing nitric acid) and vulcanized rubber (which can exude sulphur); the negative azide test also ruled out horn, a common (though stable) button material.

The matte appearance of the buttons makes gutta percha more likely than shellac, though neither presents a hazard to the bodice fabric. A natural latex produced from the sap of the tropical tree Palaquium gutta, gutta percha is a very stable material; it hardens as it ages, but does not release any harmful materials. In the nineteenth century, its insulating properties were employed in the earliest undersea telegraph cables. It was also used to make highly ornate moulded furniture, "mourning" jewellery (because of its dark colour and ability to be moulded) and pistol hand grips (hard and durable). Golf balls with a solid gutta-percha core revolutionized the game. And gutta percha is still in use. Because it does not readily react within the human body, if you have had a root canal, it was probably used to fill the empty space inside the tooth.

So the buttons will be attached to the bodice. They will be backed with a strip of cotton twill tape inside the front opening to take the strain of the stitches, and to make it less risky to remove the stitches from the silk, should that be required in the future. The work will be well documented, so that it will be clear to researchers in the future that the addition of the buttons was done by conservators in 2010.

1 comment:

  1. Robert Waller22 November, 2010

    What a great capsule description of what (and why, and how) you are doing!

    Thanks Colleen.


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