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CURRENT COLUMN

Why Paper Discolours (Part 2)
Why Paper Discolours (Part 2)

Why Paper Discolours (Part 1)
Why Paper Discolours (Part 1)

Mending a Tear in an Aboriginal Drum
Mending a Tear in an Aboriginal Drum

Distortions and Dimensional Changes
in Paper (Part 3)
Distortions and Dimensional Changes
in Paper (Part 3)


Distortions and Dimensional Changes
in Paper (Part 2)


Distortions and Dimensional Changes
in Paper (Part 1)

After treatment
Oscar Cahén: Innovative Conservation
for an Innovative Artist

Structural
Rigid Water Gels: New Treatment Options for Paper Conservators

Structural
Structural Remedies for Canvas Paintings

Digital
Organizing and Preserving Collections - Part 4: Digital-based Material

Photos
Organizing and Preserving Collections - Part 3: Photo-based Material

Organizing and Preserving Collections - Part 2: Paper-based Material

First Steps
Organizing and Preserving Collections - Part 1: The First Steps

Natural Dyes
The Use of Natural Dyes in Textile Conservation

Butterfly
A Relocation Project

Challenges of Preserving Contemporary Artwork

Preserve Your Investment through Art Conservation

A Project Completed: Heritage Preserved

Old and New Methods for Cleaning Paintings

I Can See Clearly Now – Or Can I? Part 2

I Can See Clearly Now – Or Can I?

The E.J. Hughes Mural: An Expanded Project

Is She or Is She Not an Emily

Treating Art with Sensitive Media

Malaspina Mural: An Update

For the Artist: Testing Your Materials

Conservator as Art Historian

Alum Sizing and the Art of W.J. Phillips

Treatment of an Elizabeth Keith Wood Block Print

Structural Treatment of an Emily Carr

The Treatment of a Monumental Wall Hanging

Changing Images

Preserving a Rare Record

Gold Leaf: Imitation and Genuine

The Case Against Canvas Backings

Heritage Colours: Research Discovers Original Colours

Lighting Your Art: Balancing Seeing and Protecting

The Double-Sided Emily Carr Painting

Choosing a Period Picture Frame

How to Identify a Picture Frame

Stretching Canvas and Restretching Artwork

Mounting Textiles

Aging Paintings:
Some Causes and Effects

Chine Collé Prints

What's Your Favourite Color?

Backing Removals

Rips, Holes and Tears

Filling in the Gaps

DIY – Preventative Care of Paintings

Frame it Right

Fire, Water and Smoke-Damaged Paintings

Inherent Vice

Saturated Problems:
A Water-Damaged Painting

Moldy Paper

Conserving Time

Conserving Paper: Dos and Don'ts

Repair of Textiles

Conserving Wood

Rescuing Endangered Murals

Repairing Acid-Matte Burn

Art Services & Materials
Exhibition Openings & Events


Conservation Corner Back

Some of the chemicals used to remove or inactivate iron in paper

Some of the chemicals used to remove or inactivate iron in paper

Iron in Paper: Problems and Current Solutions - Part 2

by Rebecca Pavitt
www.fineartconserve.com

Most of the conservation research regarding treatment options for Fe(II) catalyzed oxidative damage, sometimes displayed as discoloration and foxing in paper is focused on stabilizing iron gall inks in archival collections. As a conservator, my aim is to apply the findings of this research to address problems posed by iron contaminants that may be scattered throughout the paper sheet and develop an effective cleaning and stain reduction system whether the paper contains iron or not.

Treatment steps in such systems might include the following. Some modification may be necessary to protect sensitive media or paper surfaces, and in some cases treatment is not possible. (Keep in mind that Fe(II) ions are catalytic and water soluble; Fe(III) ions are insoluble.)

Water treatment: Uses solutions where the conductivity is tailored to optimize soil removal. This treatment removes soluble discoloration and some catalytic Fe(II) ions as Fe(II) is water soluble. (See Wolbers’ World: a Workshop Review in the September 2012 issue).

Reduction: Reducing agents or bleaches like sodium dithionite and sodium borohydride reduce overall discoloration and stains and convert some insoluble Fe(III) to water soluble Fe(II).

Chelation: Chelators are weak organic acids that can sequester metal ions and remove intractable soils that surfactants and water alone can’t budge. Citric acid and EDTA are two chelators sometimes used in paper conservation that reduce overall discoloration and stains and sequester some amount of Fe(II) and Fe(III).

Citric acid has less binding power than EDTA, which can be an advantage when treating items with vulnerable colours. The stronger binding powers of EDTA are useful, but can be hazardous to the media. Rinsing well after chelation is essential as any residual EDTA allows it to join catalytic Fe(II) and hydrogen peroxide in the same molecule a combination likely to trigger the dreaded Fenton Reaction: in a few weeks or months, the previously cleaned paper can become heavily spotted and discoloured.

Phytic acid may provide a better option than EDTA as phytic acid does not bind with hydrogen peroxide; any phytate-Fe residues that might be left in the paper after treatment are so efficiently bound that they remain chemically inactive. Because phytic acid is only slightly weaker than EDTA, media vulnerability is a consideration.

Oxidative bleaches: The above treatments may eliminate or minimize the need for oxidative bleaches. Gentle light bleaching may be sufficient and chemical bleaches can be applied in rigid gels for very targeted treatments.

Alkaline reserve: Raising the pH of the treated paper to the 8-8.5 range binds a proportion of any residual Fe(II) into insoluble hydroxides preventing further catalytic activity. Alkaline reserves also protect against future acid hydrolysis, which causes yellowing.

Antioxidants: More research is required, but antioxidants will likely be used in the future to prevent metal-catalyzed oxidative damage.

Resizing with gelatin: Creates a protective barrier between the paper and the outside environment to slow down the absorption of airborne pollutants like peroxides and buffer changes in Relative Humidity (RH).

Environmental controls: High humidity promotes chemical reactions, including iron catalyzed oxidation. RH-conditioned sealed framing and storage systems are protective. Moderate temperatures also reduce chemical reactions.

This summary of treatment options for paper conservation is intended for the general public. Chemical concentrations, modifications and pH ranges for their safe use have not been included.

Previously: Iron in Paper: Problems and Current Solutions - Part 1
Next issue: Disney Artist’s Legacy Lives On

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 Thu, Apr 4, 2013