I have used sodium dithionite and EDTA to successfully remove rust stains
from cotton - you can read a brief description of the technique in the NATCC
Preprints from 2002.  I combined the two reagents in one solution, and
applied it locally in a methyl cellulose gel.  It was very successful, the
one drawback being that the methyl cellulose leaves a slight residue even
after local rinsing.

Deborah Bede
Stillwater Textile Conservation Studio, LLC
Bradford, NH 03221
(603) 938-2310
(603) 938-2455 fax
[log in to unmask]
www.stillwaterstudio.org