Extracting natural dyes from wool--an evaluation of extraction methods

Area of Science:

• Textile Chemistry
• Analytical Chemistry
• Art Conservation Science

Background:

• Natural dyes were historically significant for textile coloration.
• Traditional methods for dye extraction from textiles can be inefficient.
• Understanding historical dyeing practices requires effective analytical techniques.

Purpose of the Study:

• To evaluate and compare eight different natural dye extraction procedures from wool.
• To identify natural dyes present in an 18th-century Arraiolos carpet.
• To validate a novel extraction method for historical textile analysis.

Main Methods:

• Extraction of natural dyes from contemporary wool samples using eight different methods.
• Analysis of extracted dyes using Liquid Chromatography-Diode Array Detection (LC-DAD).
• Identification of dyes in historical wool samples using LC-DAD-Mass Spectrometry (LC-DAD-MS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Main Results:

• The Na(2)EDTA in water/DMF (1:1, v/v) extraction method demonstrated superior efficiency for a wide range of natural dyes.
• This method enabled the identification of multiple weld (flavone derivatives) components in a historical Arraiolos carpet sample.
• Brazilwood and indigo were confirmed in the carpet, with Brazilwood's use being historically documented but now analytically verified for the first time. Alum was the primary mordant, with iron detected in darker hues.

Conclusions:

• The Na(2)EDTA/DMF extraction method is highly effective for analyzing natural dyes in wool, including historical samples.
• This technique facilitates the identification of specific natural dyes and their components, aiding in the authentication of historical textiles.
• The study confirms the use of specific natural dyes and mordants in 18th-century Arraiolos carpet production.