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Where were they produced, under what conditions, and at what cost?
Three weeks ago, on Friday, May 15th, Holly Hummel and I (Arden Kirkland) had a wonderful visit to Vassar's Chemistry Department. We met with Stuart Belli and Edie Stout, who were very generous with their time and introduced us to two different instruments, which in turn introduced us to a whole new world of fiber analysis.
First they introduced us to the Fourier transform infrared (FTIR) spectrometer, which measures how infrared light is absorbed by a substance. This is a non-invasive technique. We started by placing small fragments of fabric in the spectrometer (one at a time) to analyze them, but later in our session Edie was able to test the sleeve of her shirt while she was wearing it! This has great potential for analyzing fibers of textiles without needing to remove a sample. The most common method for fiber analysis in a costume shop (vs. a lab) is to do a burn test, which requires that you remove a sample from the textile and essentially destroy it. Standard microscopy is also possible, but even for that I believe you would usually want to cut a small sample to place on a slide. A non-invasive technique is greatly appreciated.
By comparing our results with those from a known sample, we were able to easily recognize patterns and determine composition. Our samples included the silks from the dress discussed in this project, and a few other samples. They had samples of silk, wool, and cotton that we could compare. We also discovered that Holly was wearing a linen shirt, so we analyzed her shirt (again, while she was wearing it) to have a linen to compare, as well.
We were pretty sure that the samples from this dress were silk, and the spectrometer easily confirmed that. Here's the result from our analysis of the skirt lining, which shows a typical pattern for silk:
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| From Chemical Analysis |
On the simplest level, this makes it very easy to determine if something is silk or wool or cotton or linen, etc., and in a non-invasive way. On a more complex level, we see a potential to look for subtle differences in a larger sample to determine more specific variations, for example identifying regional differences in textiles, or dating textiles by identifying other compositional factors involved in the manufacturing of different time periods.
Next, we went upstairs to experiment with the XRF (X-ray fluorescence) spectrometer. We inserted the same samples. In this case, the instrument was able to analyze the presence of certain specific elements. This was particularly interesting for our silk samples, which we believed had been weighted with metallic salts, as was common in the late 19th and early 20th century. This weighting unfortunately leads to an increased rate of deterioration. We were hoping to prove that they were weighted, and to find out what they were weighted with.
Indeed, all our silks were found to be weighted at least with zinc. Our worst offender, the silk gauze (badly deteriorated) that formed the sleeves, was found to have not only zinc, but also iron, copper, potassium, and lead. Here's the analysis of that gauze:
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| From Chemical Analysis |
We're very excited about the potential to analyze more of the textiles in our collection. There's a lot more to be figured out here, but this is a great beginning. Next comes the "So What?" Why add zinc or copper or lead to silk? How were they added? We've started by looking at similarities, but over time it may be more interesting to look at differences. We're hoping to find some students who are interested in both science and design who might want to take this on as a project. Design meets Science! Costume History meets Chemistry! This is a great example of what a liberal arts education is all about.
3 comments:
That is exciting! Usually in museum labs, we identify these (natural) fibers with the microscope. Their basic structures are easily recognizeable with your standard bench microscope using a tiny sample. We might use a spectrometer to identify synthetic fibers, stains, or degradation products.
That is exciting! Usually in museum labs, we identify these (natural) fibers with the microscope. Their basic structures are easily recognizeable with your standard bench microscope using a tiny sample. We might use a spectrometer to identify synthetic fibers, stains, or degradation products.
Those are some fabulous results on the weighting agents! I'm all tickled about that.
Here's some more interesting tidbits about silk fibers: Mr. Silkworm makes them as twin-filaments! The two strands (fibroin) are held together with gunk (sericin). When silk is turned into silk thread and then silk fabric, it has to first be degummed, which washes away the sericin and seperates the two filaments into two shiny strands (tah dah! silk!). As to the 'why' of adding all those nasty metals to silk fibers, _Chemical Principles of Textile Conservation_ explains 'Weighting (known also as loading) of silk has been carried out for centuries to rectify the wieght loss caused by degumming and to achieve a stiffer and crisper handle' (2005 p. 104). So there you go.
On top of being a wonderful example of awesome liberal arts are, this is also a great example of what CONSERVATION is all about! Send us your poor, your tired, your huddled masses, yearning to analyze fibers!
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