U.S. Department of Justice

Federal Bureau of Investigation

April 1999   Volume 1   Number 1

Chapter 4 of Forensic Fiber Examination Guidelines

Appendix C:
Choice of Extractants

Dye classification indicates the best extraction solution for a particular fiber. Useful published information is summarized in the following table.

Dye Class	Fiber Type/ Reference	Extraction Solution
Acidª	Polypropylene/11	Pyridine/Water (4:3)
Acid	Nylon/7
Acid	Wool/17
Acid	Cotton/14	Glacial Acetic Acid (1:1)
Basic	Polyester/7	Pyridine/Water (4:3)
Direct	Cotton/12
Disperse	Polyester/7
Disperse	Polypropylene/11
Disperse	Acetate-Triacetate/9
Metalized	Wool/17	2% Aqueous Oxalic Acid then Pyridine/Water (4:3)
Metalized	Polypropylene/11
Basic	Acrylic/13	Formic Acid/Water (1:1)
Reactive, Sulfur, Vat, Diazo, Ingrain and pigmented dyes do not extract

ª Dyes rarely extract from polypropylene, but if they do, they are most likely to be acidic.

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FORENSIC SCIENCE COMMUNICATIONS   APRIL 1999   VOLUME 1    NUMBER 1