Removing water or rust stains from paper

[paul-f]

Does anyone know how paper conservators remove stains from paper products or have any good techniques to recommend?

It would be useful for restoring telephony documentation or cleaning up phone-related items like number or instruction cards.

A quick search found references to the topic, but not much in the way of guidelines.  Here's one:

Light Bleaching: Scientific Investigation of Various Effects on Different Properties of Several Old Papers
Marion Verborg, Paper Conservation Fellow, Conservation Center for Art and Historic Art and Artifacts
 

   
• Light bleaching used for textiles for many centuries; sunlight on damp grass or in various alkaline baths
• Used less during the 19thC because of new chemical bleaching agents
• 1980 saw a revival of the method, artificial light started to be used
• Advantages of artificial light: can be used anytime of day/year, spectral distribution can be controlled, distance from light source can be adjusted
• 2001 introduction of the metal halide lamps (used in greenhouses); light used at PMA is 1000 watts)
• Goals are to improve aesthetic qualities; increase visibility of dark or illegible areas; remove by rinsing or stabilize by alkaline bath
• applications: yellowing, window mat burn, tide lines, darkening due to contact with acidic materials; not efficient on mold stains or metallic stains or lignin-containing paper
• Experimented with a variety of papers, rag, wood pulp and lignin-containing. Best results with rag.

A Comparison of the Use of Sodium Metabisulfite and Sodium Dithionite for Removing Rust Stains from Paper
Seth Irwin, Alaska Paper Conservation
 

   
• The Devil's Thumb Climbing Log: manuscript on paper with multiple severe rust stains
• Iron (III) is not soluble in water so a reducing agent is needed (sodium dithionite/sodiumhydrosulfite); use a chelating agent to allow solubilized iron to be reduced
• Sodium dithionite is a spontaneously combustable substance, requires hazmat shipping, sulfuric fumes, absolutely requires the use of fume hood, expensive
• Sodiumhydrosulfite Na2So2O4; adding one oxygen yields Na2S2O5 (sodium metabisulfite) which is also a reducing agent used in photography, does not require hazmat shipping, less expensive, far less toxic, dos not require the use of fume hood, not as expensive
• Results sodium dithionite: removed all corrosion in all samples; sodium metabisulfite removed minor stains but not heavy stains
• When to use sodium dithionite: when cost is not a concern; when treatment time is a concern; on very heavy rust deposits; if you have VERY good ventilation; if you are in a location that can receive hazmat shipments
• When to use sodium metabisulfite: when cost is a concern; when treatment time is not a concern; on most light to medium rust stains; if good ventilation is a concern; if you are in a location that cannot receive hazmat shipments easily; with oversize artifacts that are too big for a fume hood and you don't have a good above-sink extraction system
• Precautions: both reducing agents react specifically with iron compounds, must test before starting treatment; extended washing times needed; if all iron (II) is not cleared the solution will re-oxidize somewhere else on the paper; sodium dithionite is VERY hazardous and should be used in a fume hood w/ appropriate safety attire
• Extreme caution and warning of further needs for experimentation!

https://prescan.wordpress.com/2011/06/03/aic-2011-day-three-notes/

and another...

http://cool.conservation-us.org/coolaic/sg/bpg/annual/v30/bp30-05.pdf

[unbeldi]

I was going to comment on Doug's finding of the stained number card.

I do think these rust stains can be reduced.  I have looked into this a couple of times, but still not acted.

Postal stamp collectors also use a variety of techniques to remove stains, but the techniques are usually considered almost like forgery.

With paper one really would like a slightly alkaline pH so not to add anymore acid into the paper which is the main cause of yellowing and breakdown.

Rust stains result actually not only from contact with solid iron like the ends of the dial shaft, but simply also from deposits from air.

[tallguy58]

I heard that naphtha is used to clean documents. I've always wanted to try it on some old comic books.