Preserving Flak-Bait's Fabric Panels

Posted on Thu, August 15, 2019
  • by: Lauren Horelick and Meghann Girard
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The Museum’s Martin B-26B Marauder Flak-Bait is remarkable for not only surviving World War II but also for surviving the subsequent 75 years in an amazing state of preservation. We are currently working to ensure its state of preservation well into the future by performing a number of innovative conservation treatments. This is the second installment in a series of blogs on the treatment of Flak-BaitRead about how we preserved doped fabric in the first installment.

To the best of our knowledge, Flak-Bait is the only World War II bomber of its kind to retain the original insulating fabric panels lining the interior of the forward fuselage. This is one of the many unique details that supports this aircraft’s attribute as a true survivor. The image below shows the insulating fabric panels inside the forward fuselage’s radio navigator’s compartment, before treatment began. 

inside of bomber aircraft

The majority of the 50 fabric panels were damaged from a pest infestation followed by a heavy- handed restoration done in the 1970s before the forward fuselage went on display in the World War II Aviation gallery. In a traditional restoration approach, these severely damaged panels would be replicated using new materials. However, the main goal of the current Flak-Bait project is to save as much original material as possible. The project team decided that the rarity and historical significance of these components warranted the time and effort to preserve these original textiles. After three years and over 1,300 hours of effort, the fabric panels are now finally ready to return to their proper places inside of Flak-Bait’s forward fuselage. 

Our aim in sharing our work is two-fold.  This is a unique opportunity for the public to see interior details of the aircraft that otherwise would remain out of view, and it is also an opportunity for us to share our innovative process and discoveries.

Three different methodologies were developed to stabilize the panels and to compensate for the losses caused by insect damage:  

  • Technique 1 used laser-cut fills to create perfectly-shaped fabric inserts using replacement fabric.
  • Technique 2 utilized a method called “needle-felting,” which integrates felted dyed wool fibers into areas of small losses.
  • Technique 3 employed a lining process to support the remaining traces of original fabric where the insects caused severe damage. 

Before we undertook treatment, we needed to understand what materials the fabric panels are constructed from, as this helped in finding sympathetic (mending or repairing with materials that have smiliar physical properties to the original materials) and easily reversible repair materials. 

The majority of the fabric panels are constructed from green or brown dyed fulled wool, lined on the reverse with a thick layer of cotton batting. This fabric structure is machine-sewn around a support border of perforated aluminum strips. Cadmium-plated steel buttons are fed through these perforations, thereby securing each panel to the interior walls of the aircraft’s nose. 

No two panels are alike. They come in all different shapes and sizes with various cutouts that leave room for instrumentation and wiring. The images below illustrate the variety of shapes found in the interior nose fabric. Fading from years of light exposure, water exposure, and other condition issues have created variations in tone and color across many of the wool panels. 

three photos of brown fabric panels on a gray table

Technique 1: Laser Cut Fills

  • Two photos of the same brown fabric panel; top photo shows wear and discoloration; bottom panel is recently conserved

    Before (top) and after (bottom) example of a fabric panel from inside Flak-Bait’s cockpit.

  • two photos of the same panel, before and after conservation

    Before and after example of a fabric panel from inside the cockpit.

  • two photos of a fabric panel, one before conservation one after

    Before and after detail of an area of insect damage to a fabric panel from radio navigators section of Flak-Bait.

In order to make sympathetic repairs, we needed to find a replacement fabric with a similar texture and appearance to the original fulled wool to “patch” the loss areas. We discovered that pool table fabric had a very similar nap and weave as the original material used on the aircraft. We purchased several yards of this undyed fabric and had it commercially dyed to match the two primary colors, brown and green.All of the moth damage losses were traced on clear Mylar and this tracing was scanned into a computer to create a vector map. We used a Kern HSE Class 4 laser to cut out the precise shape of the losses according to this vector map (Figure 6). Once the fabric fills are cut out they are meticulously hand-sewn into place with dyed hair silk, as shown in the images below. This action serves to both compensate for the loss and provide much needed stability to the fragile fabric panels. 

  • close-up view of fabric being cut with laser cutting

    Detail view of the precise fabric fills in the process of laser cutting. 

  • man and woman look at a larger laser cutter

    Conservation fellow Meghann Girard and exhibits specialist Adam Bradshaw watch the laser cut the fills from the dyed pool table fabric.

  • A woman with brace on hand sews gray fabric

    Meghann Girard hand-sews the laser-cut fabric fills in place.

  • gray fabric panel

    Overall view of a fabric panel with the laser-cut fabric fills in place (before color-compensation).

Due to the varied coloration of the original fabric, the color of the commercially-dyed pool table fabric did not exactly match that of every panel. Archival-quality colored pencils were used to tone the fills in-situ (in their original place or location) to allow the stabilizing laser cut-fills to visually integrate into the surrounding original fabric. This prevents the contemporary treatment materials from distracting away from the original WWII fabric, which results in a more unified appearance. 

Overall view of a fabric panel from Flak-Bait after the laser-cut fills had been toned with colored pencils to match the surrounding fabric.

Technique 2: Needle-Felted Fills

Before and after detail of a needle-felted fill.

Our second process adapted an established textile conservation treatment developed by our colleagues at the National Museum of the American Indian referred to as the “Hole-istic Compensation” technique. Using this process, dyed wool fibers are needle-felted into areas of loss onto a support fabric. Many of Flak-Bait’s fabric panels had small losses dispersed between the larger losses, as seen above, and these areas were too small to fill with the laser-cut fabric technique.

In order to match the original color of the fulled wool, we dyed hair silk and wool fibers with a brand of acid-based dyes specifically used for silk and wool, called Lanaset®. 

The dyed wool fibers are then carded together to achieve a color match. A small amount of wool fibers are then needle-felted onto a piece of Reemay (spunbound polyester). This was done either in-situ or separate from the panel. The Reemay with the attached felted fill is then stitched onto the reverse of the panel using dyed hair silk. 

  • Beakers with dye and wool fibers on a scale

    Wool fibers undergoing the dye process in the Emil Buehler Conservation Lab.

  • 13 wool fiber samples of various colors

    A selection of Lanaset wool fibers and hair silk dyed by Museum conservators.

  • Close-up of hands needle-felting

    Needle-felting in progress.

Technique 3: Lining

Before and after treatment example of a fabric-lined panel.

We used a third technique to stabilize and reintegrate moth damage where the original fabric was too fragile to employ either of the two processes just described. The majority of the panels where this treatment was required are from the cockpit where light and water damage has discolored the fabric to a purple shade as seen in the image above. 

Cotton muslin was first toned with washes of acrylic paint to match the varied coloration of the original wool. This fabric was then inserted between the wool and cotton batting layers and stitched into place with hair silk. This lining provided overall stabilization to the panels and helped diminish the disfiguring areas of damage. 

View into the cockpit of Flak-Bait after the treated fabric panels were re-installed July 2019.

The Flak-Bait preservation project illustrates the benefits of taking an interdisciplinary approach to develop unique preservation techniques where collaboration and creativity can inspire new methods of preserving our treasured collection. Original material was preserved by integrating new materials to restore physical integrity while returning the panels to their original appearance.

Through this process, we have ensured that Flak-Bait will continue to be regarded as a truly unique and incredibly authentic survivor from WWII. This groundbreaking and pioneering process is much more involved than we can discuss in this short blog, but it represents the level of commitment that Museum staff have towards ensuring the preservation of our nation’s aerospace heritage.

We would like to thank the many people at the Museum who contributed ideas, time, and effort to completing this project. Special thanks to past Engen Conservation Fellow Arianna Johnson and intern Abigail Rodriguez for their work, and to our colleague Susan Heald of NMAI for her consultations. A special thanks to Gretchen Reamy for volunteering hundreds of hours of meticulous hand-stitching. 


Lauren Horelick is the objects conservator for Flak-Bait.

Meghann Girard is an Engen Conservation Fellow who helped develop and execute the treatment techniques described here.

All images courtesy of Meghann Girard and Lauren Horelick unless otherwise specified.