May I referr everybody to the chapter "Cleaning by chemical reactions" in
the book "Chemical Principals of Textile Conservation" by Agnes Timar and
Dinah Eastop (Butterworth, Oxford 1998, pp.215-236, especially pp.225-236
for bleaching).
All the chemicals mentioned in the previous postings are essentially
oxidizing bleaches, meaning that a change (of colour and chemical structure)
is achieved on the textile fibre by further oxidizing (damageing), in order
to visually obtain a unstained textile. The other bleaching option is
reducing agents (like sodium borohydrate), which transforms the brownish
areas of plant fibres into colourless form and subsequently can (and have!!)
to be rinced out, depending on the staining maybe even with additional use
of complex binders.
Bleaching is a process hardly ever used anymore in Textile Conservation. If
so, reducing agents would maybe be the better choice (of course only after
careful evaluation, and only for uncoloured textiles).
To close, I would like to cite from the above mentioned book (p. 225):
"Bleaching is a destructive process. In the past, bleaching was a quite
widely used method, but in more recent times it has been undertaken much
less frequently. Although attempts are made to "control" the bleaching
process so that minimum deterioration is caused to textile fibres, some
damage cannot be avoided." .... " In bleaching, the chromophoric systems of
discolouring materials (including aged fibre polymers) will be changed so
that their length decreases, resulting inlighter colours."

Sincerely,
Karin von Lerber

N.B. I really enjoy the tipe-o of the first posting: "The active ingredient
is sodium *perforate*", as it might really perforate your historic
textiles...
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