Categoria: Coverlet

Bleach Season at MTS

5/31/2016

We have been bleaching and wet cleaning a variety of textiles this spring at Museum Textile Services, including christening gowns, wedding gowns, coverlets, lace, and embroideries. Our favorite method employs the reductive bleaching agent sodium borohydride (NaBH4). Wetcleaning cotton and linen fibers with the addition of a sodium borohydride bath is beneficial both visually and chemically, resulting in healthier and brighter artifacts. Sodium borohydride cannot be used on protein fibers—such as silk and wool—because they are naturally acidic and the sodium borohydride solution is alkaline (approximately pH 10).

Christening gown, before bleaching.

Christening gown, after bleaching and blocking.

As cellulosic textiles age, hydroxyl groups (-OH) are converted to carbonyl groups (=O), which contribute to a dingy brown or yellow color. The chemical process known as reduction adds electrons to the cellulose fibers, stabilizing their molecular weight and returning carbonyl groups back to colorless hydroxyl groups. The combination of dissolved soils and cellulosic degradation often turn the wash bath the color of strong tea. The reaction of the sodium borohydride with water is also produces hydrogen gas bubbles, and the bath may give off a smell reminiscent of sulfur or chlorine. It is important to agitate the wash bath regularly to allow all sides of the textile to come in contact with the surface of the water where the chemical reaction is taking place.

Coverlet before bleaching (left) and after bleaching (right). Courtesy of Adams National Historical Park.

Paragon embroidery after bleaching.

Remarkably, sodium borohydride is a color safe way to bleach cellulosic textiles. Along with many white coverlets and quilts, we have bleached embroideries and samplers that have a linen or cotton ground and multi colored cotton thread. First, we test the color fastness of the colored threads. If there is dye bleed, the object is not a good candidate for full immersion wet cleaning. We have also had success bleaching a white rayon wedding dress from 1947. Rayon is a synthetically produced cellulosic fiber with a naturally high pH just like cotton, linen, and other plant fibers.

Coverlet, before bleaching. Courtesy Adams National Historical Park.

Coverlet, after bleaching. Courtesy Adams National Historical Park.

If you are a textile conservator with experience in wet cleaning and bleaching historic artifacts, you may be interested in our MTS Handout, Bleaching Textiles with Sodium Borohydride, available on the MTS website.

Morgan Carbone has a BA in Art History from Grinnell College. She recently finished her Master of Arts degree in Fashion and Textile Studies at the Fashion Institute of Technology.

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Hail to the Chief

10/24/2014

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The votes are tallied and our readers' favorite textile from 2014 is the Presidential coverlet! There is no mistaking its symbolism, importance or date. What we discovered as we began our research, however, was just how unusual this textile is in many ways.

The blue-dominant, or "right" side of the presidential seal coverlet.

The coverlet bears the seal of the President of the United States and the date 1831. The eagle seal was used as early as April 1789, and the date of 1831 is probably the date the coverlet was woven. It is a double weave, meaning that there are two sets of warps and two sets of wefts. In this case, there is a blue wool and a white cotton of each element. When the white warp is on the front, the blue warp is on the back, and likewise with the weft, creating a mirrored image.

Upon arrival, the coverlet was dirty and discolored with several areas of damage, including a large swath of missing blue yarns along the bottom edge. One possible explanation for this is insect damage--the blue is wool and attractive to moths and carpet beetles. The large loss may also have been caused by abrasion or wear; we'll never know for sure.

After this project had been signed under contract, a new book was added to the MTS library entitled Weaving a Legacy: The Don and Jean Stuck Coverlet Collection. The catalog was written by Clarita S. Anderson for a 1995 exhibit at the Columbus Museum of Art. We were excited to find that Plate 7 of this book is a nearly identical Presidential coverlet. The most notable difference between the two is that the illustrated coverlet has a fringe on the sides and bottom and does not have the same pattern of damage. Like our client's coverlet, this one is yellowed from cellulosic degradation. We easily solved the problem by wetcleaning our client's coverlet and drying it beneath a cotton wicking sheet. Although the water had run clear when we had finished washing the coverlet, when it was dry the wicking cloth showed a great deal of additional discoloration and soil that was trapped in the plush yarns.

The white-dominant side of the coverlet.

Plate 7 of Weaving a Legacy by Clarita S. Anderson is a nearly identical coverlet. Columbis Museum of Art, Harry N. Abrams, 1995.

We also learned from Anderson that, at the time of her exhibition, only four quilts were known bearing the Great Eagle Seal, ranging in date from 1810 to 1830. She appears to have not known any additional matching coverlets.

Intern Kate Herron dyeing wool yarns for the restoration.

Intern Kate Herron restoring the presidential coverlet.

Anderson's essay attributes the illustrated coverlet to New York based primarily on the fact that it has quite an early date (1831) and is a full 76 wide with no center seam. She explains that such early dated coverlets have only been found in New York and New Jersey. Of the 1,824 New York coverlets known, only 29 are dated 1831 or earlier and are seamless; of the 253 New Jersey coverlets known there is only one full-loom width example dated to 1831 or earlier. The coverlet treated at MTS was purchased on auction in upstate New York by a collector who lives in the region, which seems to corroborate the New York origin.

Area of damage before restoration.

Area of damage after restoration.

The owner of the coverlet treated by MTS opted to have us restore the pattern in the damaged area of his coverlet. MTS intern Kate Herron was given the daunting task of dyeing wool yarns to match the original. She used natural-colored Appleton two-ply yarn and dyed them with Jacquard acid dyes to a bright navy color. Kate then drafted the woven pattern onto paper as a guide. She first floated new vertical wool warp and then wove in the blue weft. All of the white cotton yarns were in place--Kate only had to pass the new yarn over and under itself on both sides of the coverlet. It was no easy task but the results are excellent and would fool the eye of all but a trained textile specialist.

Camille Myers Breeze founded Museum Textile services in 1999. She is a prolific author, and educator of museum personnel and emerging conservation professionals in the US and abroad.

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Conservation Bleaching with NaBH4

6/27/2013

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By Jen Nason and Camille Myers Breeze

One of the procedures regularly practiced at Museum Textile Services is the science of wetcleaning. We use the term “science” because it truly is just that.

Knit bedspread before sodium borohydride treatment.

Many textile conservation labs like Museum Textile Services use a deionized water system. Although water alone is a strong cleaning agent, we may also employ a mild surfactant (similar to soap) to encourage additional soil removal. Occasionally we will also use bleach to improve the appearance of discolored textiles.

Knit bedspread after sodium borohydride treatment.

The favorite method of bleaching at MTS employs the reductive bleaching agent sodium borohydride (NaBH4). Other methods, such as chlorine bleaching, are oxidative processes. Sodium borohydride can only be used on cellulosic fibers, such as cotton and linen, because it is very alkaline and can damage naturally acidic fibers like wool and silk.

Christening dress before sodium borodydride treatment.

As cellulose ages, hydroxyl groups (-OH) are converted to carbonyl groups (=O), which contribute to a dingy brown or yellow color. Reduction adds electrons to the cellulose, which stabilizes its molecular weight and returns carbonyl groups back to colorless hydroxyl groups. Stains are not generally removed with the addition of sodium borohydride but the overall results are better than wetcleaning with surfactant alone. Remarkably, sodium borohydride is color safe when used at its proper strength, and MTS has safely bleached many embroideries, patchwork quilts, and other colored cellulose textiles

Christening dress after sodium borohydride treatment.

Whether or not you appreciate the science behind conservation, the results of our recent sodium borohydride treatments are quite impressive. The textiles seen here are noticeably brighter without looking over-cleaned. Most importantly, their preservation levels have been improved with a minimum of risk.

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Bleach Season at MTS

Hail to the Chief

Conservation Bleaching with NaBH4

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