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TSLAC Conservation is moving to a new digital home!  Please reset your bookmarks to https://www.tsl.texas.gov/conservation/  E-mail subscriptions will continue as always, with no updates needed.  Come visit us at our new address for upcoming posts on a POW Journal; fragile, tracing-paper maps from Texas Supreme Court case files; our upcoming exhibit, “Setting the Texas Table”; and more.  See you soon!

Pressler Map Texas

Now, where do we find “https” on this map?

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TSLAC Conservation frequently works on 19th-century federal and state volumes bound in sheepskin leather.  These volumes often develop similar condition issues: detached or damaged spine coverings and detached boards.  Aged sheepskin leather is uniquely prone to discolor when exposed to adhesives, even those that might normally be safe for use with other types of leather.

Conservators typically try to limit intervention as possible, but for these volumes, a fuller intervention offers many advantages.  Here, a fuller intervention involves removing and stabilizing the spine covering and boards, and rebuilding the underlying structure with archival paper and tissue.  This procedure solves a variety of common condition problems and allows losses to be discreetly filled beneath the leather with toned tissue.  Leather discoloration issues are minimized because adhesive need not be applied over the top of most of the leather.

This volume (during treatment) receives a fuller intervention, in which toned tissue can be applied underneath the sensitive leather.

This volume (during treatment) receives a fuller intervention, in which toned tissue can be applied underneath the sensitive leather.

Smaller repairs actually present a larger challenge.  For example, damage at the head or tail of the spine covering doesn’t warrant a fuller intervention, but it does pose many risks for leather discoloration.  TSLAC Conservation has in recent years used a 40-gram weight toned tissue pre-prepared in-house with Lascaux adhesive and applied with heat in order to work over the top of the sensitive sheepskin leather.  Heat application minimizes the leather discoloration that would likely appear with brush application, even though Lascaux is typically safer for leather.  The need for this level of caution demonstrates just how delicate sheepskin leather can become over time.

This volume (during treatment) undergoes fills and repairs over the top of the spine covering.

This volume (during treatment) undergoes fills and repairs over the top of the spine covering.

Exhibits create a conservation workflow beyond traditional treatment.  Exhibit work can include item preparation and installation, as well as broader preservation issues, such as management of light exposure, temperature, and relative humidity.  A recent exhibit extension required TSLAC Conservation to reevaluate total light exposure for the items on display.  Because light exposure is cumulative and irreversible, light is carefully monitored during exhibition to balance public access with preservation issues.

Photographs are especially sensitive to light damage, and different types of photo materials can tolerate different amounts of light.  We typically reference a standard set of guidelines from the National Park Service to evaluate acceptable gallery limits.  During our recent exhibit extension, we found that several photographs in our brightest display cases would be endangered by excessive light exposure.  We replaced these photographs with high quality reproductions for the remainder of the display period in order to preserve the originals.

A TSLAC archivist installs a photo reproduction to limit light exposure for the original photo.

A TSLAC archivist installs a photo reproduction to limit light exposure for the original photo.

In September, TSLAC Conservation worked on the Map Showing the Beaumont – Sour Lake – Saratoga Oil Fields of Texas (nd) from the Sam Houston Regional Library and Research Center in Liberty, TX.  This 60 cm x 45.5 cm map features printer’s ink on machine-made, wove paper.  Adhesive staining, tears, and losses presented challenges for its upcoming exhibit.

Map before treatment

Map before treatment

Map after treatment

Map after treatment

A sticker-style label attached to the back of the map had caused pronounced staining on the front, upper right corner.  Solvent testing revealed that a mixture of acetone, toluene, and xylene was most effective on the stain, likely indicating an acrylic-based adhesive.  Successive poultices of the solvent mixture with Fuller’s earth provided some stain reduction, but better results were achieved by rolling with a solvent-dampened swab.  Care was taken in applying the solvent mixture over a ball-point pen annotation that was revealed beneath the removed label.  This ink proved surprisingly stable in the solvent mixture.

Adhesive staining and ball-point pen ink were revealed beneath the removed label.

Adhesive staining and ball-point pen ink were revealed beneath the removed label.

The map was washed and deacidified on wet blotter to reduce overall staining and localized tidelines.  Fills were constructed of handmade, Ruscombe Mill paper toned with water-thinned acrylic paint.  Fills were cut to shape, pared along their edges for a smooth seam, and adhered with wheat starch paste.  Extensive edge tears were then mended with NARA heat-set tissue.

Toned, shaped fills await final trimming.

Toned, shaped fills await final trimming.

Recently TSLAC Conservation has been diversifying our paper mending capabilities with heat-set and remoistenable tissues.  These tissues can offer several advantages, including decreased working time and lessened exposure to water.  Such advantages are key as we prepare many items for the Sam Houston Regional Library and Research Center’s redesigned exhibit space, opening later this year.

A particularly useful heat-set tissue recipe comes from the National Archives and Records Administration (NARA.)  The recipe, presented at the 2015 meeting of the American Institute for Conservation, features an adhesive blend of acrylic Avanse and Plextol products mixed with water.  The adhesive can be cast on various weights of tissue, dried, and quickly applied with a tacking iron.  The tissue is reversible in ethanol and requires no water for use.  It is ideal for manuscripts with iron gall ink that are not otherwise undergoing aqueous treatment.  For these documents, minimizing water exposure minimizes the risk that damaging iron ions will migrate through the paper, thus requiring more intensive intervention.

Applying heat-set tissue with a tacking iron to a manuscript with iron gall ink.

Applying heat-set tissue with a tacking iron to a manuscript with iron gall ink.

Though mending with wheat starch paste is still the preferred standard, we have found the NARA heat-set tissue to be a useful alternative for specific applications.  NARA artificial aging tests indicated that optical brighteners in Avanse do not migrate into mended documents.  However, we will remain alert for future testing on this issue, as well as others relevant to the long-term behavior of acrylic-based adhesives in paper mending.

TSLAC Conservation recently attended the 45th annual meeting of the American Institute for Conservation (AIC.)  The meeting’s theme, “Treatment 2017: Innovation in Conservation and Collection Care,” was embodied in several sub-themes, including a focus on conservation documentation.  Though documentation may not be the exciting part of treatment, it is an ethical necessity to record how physical intervention may change the nature of a historical artifact to prolong its life.

In her talk, “That Poor Cousin of Treatment: Documentation and Possibilities for Simple Innovation,” Cybele Tom of the Art Institute of Chicago presented a case study in thorough documentation as multiple conservators treated one object over many years.  She found that documentation of past treatment greatly influences current treatment decisions, and she considered detailed documentation as a “love letter to a future conservator.”  For highest accuracy, documentation might include both quantitative, objective measurements and qualitative, journal-style musings on decision making. However, these idealized practices require judicious application.  In a higher-volume, collections-based workflow like TSLAC’s, a different approach is needed.

More representative of TSLAC’s workflow was the talk “Medium Rare: An Innovative Treatment Approach to the Space between Special and General Collections.”  Quinn Ferris of the University of Illinois at Urbana Champaign discussed issues familiar to many conservators who work with materials that fall somewhere between general collections and special collections.  Documentation presents a special challenge for these materials: it should be careful and methodical, while still promoting quick turnaround.

TSLAC’s solution is to create written documentation for all items using a check-box-based database, which provides a searchable, controlled vocabulary.  Additional descriptive fields allow customization and qualitative musings like those advocated by Ms. Tom.  We pursue photographic documentation only for treatments that are especially invasive or that involve items that are especially unique.  As seen at the AIC meeting, balanced solutions like ours are pursued in other, similar collections.

May is Preservation Month, and here at TSLAC we’re celebrating by launching several new environmental monitors throughout our building.  Providing a stable environment is one of the best steps you can take toward safeguarding collections.  By controlling temperature and relative humidity, you can slow the clock on natural aging processes and often avoid conservation treatment altogether.

How does environment matter from a conservation perspective?  Simply put, it impacts materials’ mechanical and chemical stability.  Mechanical damage may occur when fluctuations in temperature and relative humidity cause materials to expand or contract.  Rapid cycling of temperature and moisture is especially problematic.  This can lead to cracks, tears, and breaks.  One household example of mechanical damage can occur when pouring very hot water into a cold glass causes the glass to break.  This dramatic damage can also occur gradually over time if archival materials are improperly stored.

Mechanical damage: transcription disc.

Mechanical damage is one factor at work in the pictured transcription discs. The discs’ outer coating (cellulose acetate plastic) and inner core (glass) have reacted to their storage environment differently, causing severe cracks and losses. (Photo by Steve Kantner.)

Chemical damage occurs when materials change or weaken at the molecular level.  Chemical damage, in its many forms, generally speeds up in warmer, wetter conditions.  Without sufficient heat or moisture, some deterioration processes may never start.  Familiar examples of chemical damage driven by environmental conditions include yellow, brittle paper and silver mirroring in black and white photographs.  In archives, a particular concern is iron gall corrosion, the process by which historical ink can eat through paper.

Chemical damage: iron gall ink

Chemical degradation has caused the iron gall ink in this document to weaken its paper support. As a result, brown halos appear around heavily-inked areas, and losses are visible in the large letter “G”.

Archival environmental standards for paper-based materials are 45 – 55% RH, 65 – 72 degrees Fahrenheit.  While it’s OK for these levels to drift gradually across seasons, short-term fluctuations should be minimized.  Remember these environmental impacts as you safeguard your treasures.