Polysulphide toning of microfilm

I would like to know the latest developments on polysulphide toning of
microfilm as a means of preventing redox blemishes.  Is this still a
good precaution to take? Thank you,

Shelagh Linklater
The Provincial Archives of Manitoba
Winnipeg, Manitoba, Canada

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                  Conservation DistList Instance 8:82
                   Distributed: Sunday, April 9, 1995
                        Message Id: cdl-8-82-007
                                  ***