| 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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