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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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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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Out of the Blue

4/28/2013

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by Camille Myers Breeze

In January, 2011, Mary O'Dwyer brought us her grandfather's 1875 christening gown, to see if we could do anything to help her. We could not believe our eyes when she arrived with a pair of lovely cotton garments the color of robin's eggs. The blue was streaky and could not mask a pattern of brown stains, most noticeable on the front.

Mary O'Dwyer's family christening gown and underslip before treatment to reduce bluing.

Although most of us had heard the term "bluing" we had never seen a dramatic example in person of what could go wrong with the treatment. The principal behind bluing is that the yellowing that occurs with aging in both natural and synthetic fabrics can be neutralized with the addition of a light application of blue dye. This same principal is used by some older women on their hair, with infamous results. The active ingredient in bluing is a fine iron powder containing the pigment Prussian blue (ferric hexacyanoferrate). Several brands of laundry bluing were popular from the late 1800s, including Mrs. Stewart's, which is still sold today.

Mrs. Stewart's Liquid Bluing was founded by Al Stewart, and was first sold in Minneapolis in 1883. The image on the bottle is his mother-in-law, Mrs Stewart.

While Mary O'Dwyer was still in our studio, we pulled an old book from our library shelves and read up on laundry bluing. Laundering and Dry Cleaning, published in 1925 by the Women's Institute of Domestic Arts & Sciences, Scranton, PA, gave the following advice for bluing in section 81:

    If you are one of the housewives who use powdered or lump blue, then be sure to take great care to add a small amount of water to the powdered blue before use and to tie ball, or lump blue, in a small cloth bag, which may be dipped and squeezed in the water before using. Otherwise the bluing is likely to be unevenly distributed and cause spots to form on the clothes. In spite of these precautions, there will be this tendency unless a very few clothes are put in at one time and these kept in motion.

    If you use the liquid Prussian blue, remember that it contains salts of iron that turn to iron-rust in the presence of the alkali from soap, particularly when heat is applied, as in ironing, for example. Consequently, to avoid iron-rust stains on the material, take every care to have the clothes thoroughly rinsed so that all traces of soap are removed before bluing.

Closeup of the intricate details on this christening gown, as well as the brown stains and streaky blue tinge.

This same book states that, "If it does happen that the clothes become overblued, they may be whitened by placing them in cold water and heating them to the boiling point, repeating the process if necessary until all excess bluing is removed." However, similar attempts had already been made without success. An online source gave additional advice to "use a solution of 1 C. household ammonia to 1 qt. of cold water and soak, covered tightly for 48-72 hours. You may need to perform this procedure 2-3 times, washing with detergent following each process."

Mary O'Dwyer decided to try the treatment herself, with some trepidation. Imagine our delight the following summer when out of the blue she emailed us these photos of her family christening gown, clean and white! She reported that her granddaughter had been baptized the previous Sunday and that the dress looked beautiful. The simple ammonia soak was successful in reversing the bluing and did not leave the cotton dry or brittle.

Although we still have no first-hand experience treating blued textiles, we're delighted at the success of this old-school recipe.

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Bleach Season at MTS

Conservation Bleaching with NaBH4

Out of the Blue

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