THE INFLUENCE OF MORDANT ON THE LIGHTFASTNESS OF YELLOW NATURAL DYES
Patricia Cox Crews
THE USE OF NATURAL DYES to color textiles declined rapidly after the discovery of synthetic dyes in 1856, until they were virtually unused by 1900. Consequently, the lightfastness of only a limited number of natural dyes has been evaluated by the more sophisticated fading apparatus and quantitative techniques which have been developed over the past 50 years. Yet most textiles and costumes in museum collections were colored with dyes obtained from natural sources. The lightfastness of these natural dyes must be known so that museum personnel can make proper decisions regarding the display of an artifact.
Some researchers noted this need for modern evaluation of natural dyes.1,2 However, their studies have several limitations. First, they only evaluated the lightfastness of natural dyes that were widely used industrially in European textiles. Many more dyes, particularly in the yellow range, were widely used by settlers on this continent in the eighteenth and nineteenth centuries, and by American Indians producing their various ethnic textiles.3,4 Since these American textiles are of growing importance to museums, more lightfastness data are clearly needed.
Another limitation of previous studies was that they did not collect data on all five commonly used mordants—alum, chrome, copper, iron, and tin. Duff, Sinclair, and Stirling evaluated nine dyes with tin mordants primarily.5 Padfield and Landi did not evaluate chrome mordants at all; they they considered the use of chrome a modern technique because it was not in use until the early 1800s.6,7 But, as discussed earlier, nineteenth-century artifacts are important to American collectors. Because previous research has these limitations, lightfastness data on natural dyes are still rather scanty.
The objectives of this study were to evaluate the lightfastness of selected yellow dyes and to evaluate the effects of commonly used mordants on the lightfastness of the dyes. I selected plants which are widely available across the United States and likely to have been used by the home dyer in Colonial America, by the American Indians, and by the contemporary fiber artist.8,9 By knowing the relative lightfastness of the yellow dyes, museum personnel could make display decisions and recommendations based on the least lightfast dye in the textile. This is usually the yellow dye.
I evaluated the effects of all commonly used mordants on color because all have been in use since the mid-1800s and most have been in use for centuries.10 I also assessed all mordants because contemporary fiber artists premordant with all five mordants so that they can get five shades from a single dyebath. By assessing the mordants used today as well as in the past, I hoped that results of this study would be useful in conservation and display decisions for contemporary textiles, as well as for historical textiles.