Preserving Flak-Bait: Reversing a 1970s Restoration

Posted on Tue, April 28, 2020
favorite

The Martin B-26B Marauder Flak-Bait is an iconic artifact of World War II. This medium bomber and its crews survived over 200 missions over Europe, which was more than any other American combat aircraft in World War II. The nose section went on display when we opened in 1976, but the remainder of the aircraft has been in storage since the 1940s. Thankfully, with plans for exhibition at the Udvar-Hazy Center, where there is room to display the full aircraft, the entire artifact is now together and has been undergoing preservation treatment in our Mary Baker Engen Restoration Hangar. 

Martin B-26B Marauder Flak-Bait

The nose section of Flak-Bait before the treatment to remove the overpainting was begun.

One aspect of this preservation effort is undoing a previous restoration. In the 1970s, the nose section of Flak-Bait had layers of paint applied over the original factory applied paint. This over-painting was done to the top and bottom three quarters of the nose section in an effort to cover up areas of corrosion and peeling paint and areas where the bare aluminum alloy was exposed from its operational history.

flak-bait with green highlighting

The nose section of Flak-Bait highlighted with photo-editing software to indicate areas of the nose section that were over-painted.

In the 1970s the predominate aesthetic for interpreting technological artifacts favored the look of “new” and “undamaged.” We believe this is one of the reasons why paint was applied to the battle-scarred nose section of Flak-Bait before it went on display in 1976. Our current philosophy for the interpretation of Flak-Bait is one of celebration of its battle damage and the wear and tear of use. By highlighting the damage and revealing the original paint layers, we are returning this aircraft to a more honest and authentic state of preservation.  The Museum’s conservation department has been developing techniques to reverse the 1970s overpainting to reveal the original paint layers and previously obscured markings. 

Before we could attempt to reverse the overpainting, we needed to fully understand the paint layers, their thickness, and their solubility. We first embarked on a project to carry out diagnostic imaging with with help of a Museum photographer to better understand the complex painted surface. We used ultraviolet light (UV) photography and infrared (IR) reflectography.

UV Photography

UV photography allows us to distinguish organic materials, such as oils, resins, paint binders, and pigments from one another based on how they absorb UV light and become fluorescent.

Flak-Bait is shown below photographed in UV light. Notice how the lower row of bombs is fluorescing a pale yellow while the rest are varying shades of red.  This suggests that a different type of paint was used here. Some areas of overpainting appear as a milky yellow green between the second and bottom rows of bombs.

UV light photo of Flak-Bait

The pilot’s side of Flak-Bait in UV light.

This detail photo of Flak-Bait shows the “Flak-Bait” design and 200th mission bomb on the pilot’s side in UV light. Notice how the 200th mission bomb fluoresces a different color red than the smaller bombs—again suggesting a different type of paint was used. Overpaint can be seen in UV where there are pale and hazy blue fluorescence is located on the left of the image, below the F and L.

UV photo of Flak-Bait painting

Detail image of Flak-Bait in UV light, showing the painted “Flak-Bait” and 200th mission bomb on the pilot’s side.

The co-plot’s side of the aircraft is not often seen in historical photographs of Flak-Bait, though it is equally compelling, with a large patch located just aft of the bombardiers’ station. 

In UV light, the bright yellow drips located forward of the windscreen are quite pronounced. In many other areas of the exterior, we have various oil and grease stains that relate to the operational history of the aircraft. We aim to keep these types of surface stains as part of the narrative of the aircraft’s operational history. Distinguishing historic versus post-historic damage has been an important step in determining our treatment approach. The oil drips seen below are post-historic and likely came from the aircraft hanging above Flak-Bait while it was on display at the National Mall building. Therefore, it was decided that these oil stains should be removed.  

  • UV photo of Flak-Bait painting

    Co-pilot's side in UV light.

  • flak-bait copilots side

    Co-pilot's side in normal light.

Infrared Reflectography (IR)

flak-bait

2017 Engen Conservation Fellow Lauren Gottschlich set up to capture IR images in many small sections along the bottom of the fuselage of Flak-Bait. 

Infrared reflectography (IR) is a technique commonly employed by our colleagues in paintings conservation to see through paint layers, revealing an artist’s graphite drawings. We borrowed this technique to determine if there were signatures of the servicemen buried under the overpainting. The image below shows several IR photographs digitally stitched together. Graphite from the pencils preferentially absorbs IR light, enhancing the legibility of signatures that were otherwise obscured.

IR photography of Flak-Bait

IR photographs of the co-pilot's side digitally stitched together.

In many locations along the fuselage, a combination of overpainting and soiling obscured the handwriting, which was made legible with the IR photography, as seen in the slideshow below.

  • Two photos of Flak-Bait

    On the left, oil drips, soiling and overpainting obscured handwriting on the surface of the fuselage.
    On the right, faint signatures now seen using IR photography.

  • before and after IR photos

    On the left, van you make out anything in this area?
    On the right, IR photography reveals a tiny hard, buried under the overpaint.

Once the diagnostic imaging was complete, we had a good understanding of the overpaint and original paint characteristics. Utilizing the IR and UV images helped greatly in determining areas where the overpaint removal technique needed to be modified to not disturb the fragile graphite markings.

 

Overpaint Removal

We developed a process for safely removing the overpaint, which began with extensive solubility testing of the paint layers. In the image below, Malcolm Collum is seen carefully applying an organic solvent to the overpaint layers to determine its solubility. Once we completed extensive material analysis and solubility testing, we began removing the overpaint layers from the top surface of the nose section.

man standing next to flak-bait

Chief of Conservation Malcolm Collum carrying out solubility testing on the co-pilot’s side of Flak-Bait.

We discovered an intact layer of original olive drab paint and original zinc chromate painted scab patches underneath a lighter green overpaint. The area indicated as “original” in the image below reveals the dark colored olive drab paint layer which is the original, factory applied paint.  We also see the evidence of use and wear to the paint – particularly on raised rivet heads and along the paths where the maintenance crews walked. 

Flak-Bait paint removal

Top of aircraft during the paint removal.

Once the top of the nose section was complete, we began on the underside surfaces.  The image below shows the underside of the bombardier’s section before and after the overpaint removal had begun. On the right is the bombardiers’ section with a square of original paint revealed in the center of the image. Note the water streaking caused when Flak-Bait was left in the rain on the tarmac.

underside of bombardiers section of flak-bait

On the left, underside of the bombardiers’ section with a light blue- gray layer of overpaint.
On the right, underside of the bombardiers’ section with a square of original paint revealed in the center of the image.

Areas where signatures were covered with overpaint were handled with great care to not disrupt the markings. This example shows the signature of Alfred McBee, written between the gun blister locations on the co-pilot’s side. The areas of light blue haze that obscure most of the top and bottom of his signature is the overpaint applied in the 1970s. After the overpaint was removed, his signature has greater legibility and it’s possible to see that there are areas of loss paint. This loss is likely due to the interface of the machine gun blisters abrading the paint during firing and removal for maintenance. These losses are part of the authentic look that we want to reveal and celebrate.

signature on flak-bait

Before and after photo of a signature on the co-pilot's side of Flak-Bait. After overpaint removal the signature became more prominent.

On the pilot’s side of the aircraft, the overpaint removal did not reveal any new signatures but did bring out the original paint color. The image below shows the progress once overpaint removal began on the pilot's side, beginning from the aft. 

flak-bait closeup

Flak-Bait during overpaint removal. The interface of original and overpaint can be seen in the straight vertical line towards the aft 

Through this process we have ensured that Flak-Bait will continue to be regarded as a truly unique and incredibly authentic survivor from World War II.  This treatment 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. 


Lauren Horelick is the objects conservator for Flak-Bait.

Special thanks to Museum staff photographer Dane Penland for his assistance with both the UV and IR photography and to Lauren Gottschlich for her work capturing and processing hundreds of IR images of Flak-Bait’s surface.