Setting up for imaging

On Friday December 16^th, I had the pleasure of assisting with the hyperspectral imaging of three paintings in the Cantor Arts Center’s collection, including Andre Derain’s Still Life With Fruit (1938),  Dirck van Delen’s Solomon Receiving the Queen of Sheba (1642), and Hieronymus Bosch’s The Last Judgment (1500s).  Joyce Farrell and Torbjorn Skauli of the Stanford Center for Image Systems Engineering led the advanced imaging procedure, which employs a high-resolution MCT (mercury cadmium telluride) detector that produces digital, high-resolution true-color renderings, performs near-infra-red scans to uncover any underdrawings, and provides information about the pigmentation and other materials in the medium.  Both the Louvre and the National Gallery have also been using this system to study and photograph their collections. (See http://www.hyspex.no/pdfs/HySpex_Art_scanner_web.pdf.)

Curators, professors, conservators, and scientists collaborating at the Cantor Arts Center

What is hyperspectral imaging?  First developed for remote sensing applications, hyprspectral imaging collects information about a scene or an object from across the electromagnetic spectrum.  It is is a type of spectroscopy that collects information as a set of images. Each image represents a range of the electromagnetic spectrum, known as a spectral band.  Hyperspectral imaging deals with taking snapshots using narrow spectral bands over a continuous spectral range to produce a visual rendering of the spectra of all pixels in the scene.   To examine art, the hyperspectral imager gleans optical information  over visible (400-700nm) and near-infrared wavelength ranges (700nm to > 1micrometer), as some oils and pigments don’t fluoresce in the visible light range.  Because certain objects and materials leave unique fingerprints across the electromagnetic spectrum, the imaging technique has been applied in a multitude of ways in the fields of geology, agriculture, resource management, and medicine – to image faces, large fields, forested areas, and even pig organs.

Lubert Stryer, Professor of Cell Biology, pays a visit to the Cantor Arts Center

To measure the spectral data of the paintings, we needed two lights to shine onto the paintings, however this caused some concern when the lights began to raise the temperature of nearby paintings in the gallery above the recommended temperature of 72 degrees Farenheit.  By altering the height of the lamps and turning them off when not in use, we managed to avoid setting off any temperature alarms.

Holding a white board over the work to calibrate the light levels of the imager

The processing of these high-resolution, spatially-resolved data sets is rather complicated.  In fact, Brian Wandell and Joyce Farrell are teaching a class next quarter (http://white.stanford.edu/~brian/psy221/syllabus.html), and they hope some students from the class will be interested in analyzing the images.

Torbjorn collecting data using a portable computer

For instance, the word totem is derived from an American Indian word that means something like “member of my family” or “relative of mine.”  Given the great lengths we go to in order to care for Western paintings and sculptures and the outrage and sense of loss that occurs when a so-called masterpiece is destroyed, perhaps “member of my family” is a more accurate definition for such objects than “work of fine art.”

The words fetish and idol can be used in similar ways.  The former is traditionally defined as a object with magical properties while the latter implies a manifest, god-like entity.  While I usually think of them as describing a foreign culture or distant time, could they also apply to Western art objects?  Take the Poussin painting above as an example (the one on the far right).  Perhaps my belief in its ability to teach us about the past makes it more of a “fetish” than a work of “fine art”?  What is “fine art” anyway?  And exactly how and why is it so good at teaching us about the past?  It is after all an inanimate object that cannot actively teach anything in the literal sense of the word.  In other words, perhaps my belief in Western painting’s ability to teach has more to do with my belief in its magical properties than in its distinguished history.

One of the primary benefits of thinking through art conservation with this triad is precisely that it approaches the art object from a non-Western perspective.  It is very easy to assume that we know what art is and  what we are supposed to do with it: we display it, look at it, enjoy it, learn from it, etc.  And our conservation decisions stem from this understanding.  However, following Mitchell, I want to suggest that these thoughts wash over a dynamism that is potentially at work within every art object.  If art history has taught us anything in the past 50 years it is that the relationship between viewing subject and object viewed is far from static.

Such thought exercises are useful to art conservation because they help us elaborate our reasons and make us more aware of our actions.  Our museum setting rose out of a Western tradition and continues to be dominated by Western objects and ideas.  And if art conservation is to be a truly world wide practice we have to think through these exercises and honestly come to terms with them.  By doing so future conservators might readily ask: Does the object want to be conserved or do we want to conserve it?

One of the main obstacles conservators face is the mystery behind these techniques.  For the foundry, such secrets keep them in business; for the conservator, the fact that these details are kept a secret makes work difficult.  Even though you might be able to guess what was used to create a certain patina – Ferric Nitrate, Cupric Nitrate and Sulfurated Potash are all commonly used – the variables that contribute to the final appearance are endless.  For instance, the concentration of the solutions, the duration of application and the surface temperature of the bronze can all change the end result.  Conservators often solicit artists directly about their patination process so as to to anticipate potential future conservation needs.  While this has its advantages and has proven invaluable here at Stanford, its drawbacks are that opinions on patina often change and that people sometimes forget how a certain effect was produced or what the original parameters of production were.

"Large Torso: Arch" in the early 1970s

The lack of definite information about the exact chemicals used and the details of the patination process leaves conservators without a direct path to follow.  If they want to maintain the artist’s original intention throughout the years, they have to protect the mystery patina that is already there.  If it’s not protected the bronze will quickly corrode and the surface will begin to look more like it’s been covered in teal spray-paint than layer upon layer of subtle, chemically patinated color.  A common misunderstanding about bronzes is that the bright green corrosion that can develop over time is the patina.  In fact, the secret patinas of most foundries are almost always composed of layers of translucent color on top of each other: brown, green, black, and sometimes even blue, red and orange.  The combination of layers of colors like these builds up a surface that reacts to changing light conditions and highlights different areas of the surface.

Of course, the artist could express that they want the patina to corrode.  In fact, Henry Moore is known to have expressed this exact sentiment for certain sculptures.  However, it’s also known that he sometimes insisted on complete repatination because of a corrosion.  Moore’s fascination with and insistence upon the relationship between his sculptures and their environment supports this modifiable aesthetic.  He didn’t have a monolithic approach to maintaining his sculptures because he didn’t see them as isolated entities that could stand on their own, but rather as object that were deeply enmeshed in their environment.  In other words, the record seems to indicate that Moore’s opinion on patina depended upon the sculpture’s context.

"Large Torso: Arch" in 1998 before conservation

So the million dollar question is: what did Moore think of this particular cast in this particular location?  Unfortunately we do not have a definite answer.  However we do know that he liked the site and that he liked the appearance of the patina when it was originally installed.  So all we can do is try to preserve that appearance as best as we can.  This is why we apply a wax coating to the surface.  Otherwise, the patina would corrode entirely away.  This is also why we don’t apply a thicker, more protective and more opaque coating.  Because we know he like the sculpture as it looked when it was first installed.

"Large Torso: Arch" in 2003 after conservation

A portrait of Winckelmann by Raphael Mengs after 1755

Winckelmann was and continues to be a celebrated figure in the history of art because of his historicist method—most fully developed in “History of Ancient Art” of 1764.  In this work, Wincklemann not only provided the first comprehensive account of Greek sculpture but also argued that historical factors such as the climate and political freedom of ancient Greece were fundamental in producing its sculptures.  Simply put, this was the first text to argue that works of art were in some way produced by historical circumstances.  Given this widely held fact, it is unsurprising that Winckelmann is generally regarded as the father of art history.

However, Winckelmann’s legacy is complicated by the tradition out of which it emerged.  Mid-18th century Germany also gave rise to rationalist aesthetics; a philosophical school often exemplified by Alexander Baumgarten’s attempted formulation of a “science of the beautiful.”  Winckelmann attended Baumgarten’s lectures on aesthetics and at the very least was inculcated in his system of thought.  Thus, even though Winckelmann’s contextualist, historicist writing was in many ways directly at odds with Baumgarten’s universalizing, idealistic notions about beauty, he did not completely escape the dominant intellectual mode of his time.

Thus, as Ivy pointed out, Winckelmann still held idealist notions about art.  While he contextualized to some extent, he also famously argued that the “noble simplicity and quiet grandeur” of Greek sculpture made it great; this is perhaps why he preferred marble sculpture to be white.  Indeed, a white sculpture is certainly more “simple” and “quiet” than the polychrome ones we know about today.  Thus, the great irony of his legacy—and the one that  “True Colors” best exemplifies—is that while he is remembered today as the father of art history, the idealist components of his writings also led to the whitewashing and destruction of much of that history.  In other words, his writing had two contradictory effects.  He simultaneously inspired an historicist approach to art objects—one that eventually led to the professionalization of art history and subsequently the professionalization of art conservation—and he inspired an idealistic myth that the whiteness of Greek marble made it great—which led to the whitewashing and the removal of historical evidence about Greek sculpture.

The paradox of Winkelmann’s legacy is a fascinating instance of how the ideals of art and the facts of art come into conflict.  While we all  like to think that we are on the side of fact—especially when it comes to art restoration—the slope between fact and ideal is slippery at best.  (See my previous post on keeping art looking “good”)  But don’t just take my word for it . . . visit “True Colors” and see the facts for yourself.

In front of the Conservation Lab we have three signs with the following words and their definitions:

Conservation: Conservation is the deliberate alteration of the chemical and/or physical aspects of cultural property, primarily to stabilize it and to prolong its existence.

Preservation: Preservation is the protection of cultural property against deterioration and damage by providing preventative care:

• regulating environmental conditions
• practicing sound handling and maintenance procedures for storage, exhibition, packing and transport
• controlling pests
• preparing for emergencies

Restoration: Restoration involves treatment procedures that are intended to return cultural property to a known or assumed state—for example, near to its original appearance—often through the addition of non-original material. In current restoration practice, all additions are fully removable.

The collection and stewardship of art involves a complex interplay between these three different goals. While the distinction between these three areas seems subtle, different combinations of these goals will ultimately determine how the object is treated to maintain it for future generations.

This interplay between conservation, preservation, and restoration has varied—sometimes dramatically—over time. One infamous case in the area of Greco-Roman marble sculpture—the Vatican collections—represents this evolution well.

The Vatican’s story was briefly alluded to in the “True Colors” exhibition. Long a major collector of fine art, its collections were headed in the 18^th century by Johann Joaquim Winckelmann, who published the influential “Thoughts on the Imitation of Greek Works in Painting and Sculpture” in 1755. In this book, Winckelmann stated that the best marble sculpture should be white, which led to a systematic scrubbing of many pieces in the collection and set the standard for others to follow.

Since much of this work rests on how “good” the object is made to look, the practice of caring for these objects is also inextricably tied to changing tastes. One great example of how differing tastes guide the hand of those who care for art objects is the case of the Hope Hygieia, which is now at the Getty Museum. When the sculpture was uncovered in 1797, it was popular practice to restore such broken ancient sculptures by reconstructing missing parts in marble and attaching those pieces to the original sculpture. In the 1970s, however, the prevailing museum aesthetic was to display these pieces as they were found—any modern restoration was considered a falsification of the truth. As such, many restorations—including the Hope Hygieia’s—were removed.

Thirty years later, conservators and curators are beginning to appreciate these reconstruction attempts as intrinsic to the object’s history and worked to restore the reconstructed pieces of the sculpture, which had been saved when they were removed. A more detailed history of the sculpture can be found at the Getty’s website (http://www.getty.edu/art/exhibitions/hope_hygieia/).

These restorations of the reconstruction were done using easily identifiable and reversible methods, which reflects the current trend in museum practice. And although the balance between restoration, conservation, and preservation remain in flux, that balance also means that you will not be seeing original sculptures repainted anytime soon.

Join in on the conversation: should we attempt to restore works of art to their original state, or are the changes throughout history just as important?  What do you think about performing a restoration as opposed to leaving or improving an old one?  What other ways museums might illustrate or perform these changes based on new technologies?

Casey, Christopher (October 30, 2008). “”Grecian Grandeurs and the Rude Wasting of Old Time”: Britain, the Elgin Marbles, and Post-Revolutionary Hellenism”.Foundations. Volume III, Number 1. http://ww2.jhu.edu/foundations/?p=8.

This being my first blog post, I find it appropriate to introduce myself.  I joined the Outdoor Sculpture Crew in November 2010 and I’m currently completing a graduate degree in Museum Studies at John F. Kennedy University.  After graduating from William and Mary, I moved to Palo Alto a couple of years ago.  Besides working with Oliver, I also volunteer at the Cantor Arts Center, helping to update the museum’s exhibition records.  I hope you find this post informative, thanks for reading!

Over the past few weeks, Oliver and I have been performing routine maintenance on the Rodin Sculpture Garden.  Last Thursday we tackled the largest piece in the Garden, The Gates of Hell.  While working on The Gates, several visitors approached us to ask what we were doing to the sculpture; this post explains how we maintain most of the bronze sculptures in the Outdoor Sculpture Collection.

Buffing the wax with nylon bristle brushes

By regularly cleaning, inspecting, and waxing the outdoor sculptures, we hope to prevent the need for more invasive conservation work in the future.  To clean the bronze, we initially spray it from the top down with water to soften and remove the top layer of dust, grime and bird droppings.  Then we look to see whether or not the water beads on the sculpture’s surface.  In areas where water does not bead, the previous wax treatment has worn off.  Next the sculpture is washed with a mild soap using soft sponges and brushes and then rinsed clean.  Following that, we use absorbent towels to dry the sculpture thoroughly.  It is important that the sculpture be completely dry and warm before applying wax to ease application.  Once we are sure that the sculpture is dry and the sun has gently heated its surface, we apply a hard, high melting point microcrystalline wax called Be Square 175—the number 175 refers to the melting point of the wax in degrees Fahrenheit.  Mineral spirits—a mild solvent often used as a paint thinner—is added to the wax in order to produce a thin fluid which can be readily applied to the sculpture.  When the wax has dried, we buff it twice, first with large nylon brushes, and then with a piece of fine nylon stocking.  Buffing compresses the wax into a thin, hard film, providing lasting protection, a shine to the sculpture’s surface, and a richness to the color.

The sculptures in the Rodin Sculpture Garden are cleaned every other month with wax treatments applied as needed, generally twice a year.

Detail of mineral deposits built up on the surface of a steel sculpture

So what’s the solution to this continuing need?  We can’t turn off the sprinklers or remove all the fertilizers because the landscaping – the artwork’s visual context – depends on them.  While we can prevent future mineral deposits by adjusting the irrigation, removing previous ones can be done with chelation.

The etymology of chelation is Greek χηλή, chelè, meaning claw. The term relates to chemical binding processes where multiple extending parts of a molecule surround to enclose an ion.  In the illustration below you can see how the shape of a chelator is similar to the claws of a crab.

Chelators come in many different shapes and sizes and chemical companies develop them for specific purposes. The above illustrated EDTA (ethylene diamine tetraacetic acid) is one of the most common chelation agents; it can be found in many consumer products from face wash to food. At Stanford we use EDTA and another chelation chemical DTPA (diethylene triamine pentaacetic acid) for various specialized cleaning needs – including removing the above mentioned mineral deposits. By adjusting the pH of the different chelation solutions we can further refine and optimize their effectiveness. We start by referring to published research on the different chelators. Then we mix and test several solutions on the sculptures. The solution that produces the best results gets the job. At Stanford, the continuing needs of the outdoor art collection make the competition between chelating agents as fierce as the admissions process.

Detail of the same area after a single chelation treatment

John Ruskin, "Self Portrait," 1847

This post is the second in an ongoing series on influential figures in the history of art conservation.  Whereas in my first post in this series – on Cesare Brandi – I talked about one of the first major proponents of modern conservation, here I want to look at a figure who helped define exactly what conservation meant as a practice.

John Ruskin (1819 – 1900) was and continues to be one of the most celebrated art writers of the 19th century.  In The Seven Lamps of Architecture he famously and passionately equates restoration to destruction and thereby helped set in motion a debate about the care of our cultural heritage.  ”Neither by the public, nor by those who have the care of public monuments, is the true meaning of the word restoration understood.  It means the total destruction which a building can suffer: a destruction out of which no remnant can be gathered: a destruction accompanied by a false description of the thing destroyed.”¹  Here Ruskin argues for the frailty of cultural objects and seeks to promote an absolutely noninvasive approach to their care.  For Ruskin one should never attempt to recreate the art object as is was originally created but rather one should leave it as it exists and preserve that existence.  This hands-off approach to cultural heritage was and continues to be highly influential, informing the difference between the terms restoration and conservation.

However, Ruskin’s famous comment can be easily taken out of context and understanding the historical situation that it was enmeshed within sheds light on what he meant when he vilified restoration.  Ruskin’s statement was published in the wake of the 1848 revolutions that swept across Europe, a time when political unrest and civic discontent was at a peak.   As Chris Brooks and other architectural historians have argued, during this moment Ruskin saw within the Gothic style a potential beacon through that political turmoil; the Gothic became a symbol of freedom.²  In this context, the Gothic was opposed to the Classical, where the latter was seen as representing the aristocracy and the old power structure, the former was seen as a manifestation of the creative powers of the guild system and thus of the people’s power to create.  Ruskin romanticized the guild system because of how it created its cultural objects; rather than reproducing a style of that was imposed upon it—i.e. Neo-classical style—it created its own style—i.e. the Gothic style—by organizing the creative power of its members.   However, because the guild system no longer existed at the time when Ruskin was writing, in his eyes, there was no way to restore the art it had created without simultaneously erasing how that art was created.  In other words, Ruskin was arguing that when you restore a work of art you are changing how it was made and thus the very nature of the work itself.  For Ruskin this was especially dangerous at the time because the authenticity of the Gothic style was one of the few symbols of hope in an especially trying time.

I think Ruskin’s championing of how art was made reverberates with many contemporary feelings of uncertainty about restoration.   We want our art to be meaningful today and part of that meaning undoubtedly comes from how the art object was produced.  Interestingly, Ruskin’s writing was the beginning of a debate which eventually led Parliament to audit all previous church restoration projects.³  What they learned from this survey was that of all the churches in England, scarcely a single one was preserved as it was originally built.  Did this mean that since how the churches of England were built was lost, scarcely a church was still meaningful?  Not a chance!  Rather I think it suggests that part of the meaning of every cultural object invariably comes not only from how it was made but also from how it is used.  While it is impossible to deny the legitimacy of the impulse to find an ultimately authentic work of art – indeed I sympathize with the survey that Parliament funded – I think that impulse washes over the contribution that using a work of art has to its meaning.  Clearly those churches were maintained because people wanted to use them; they knew that without a new roof or new windows soon they would be left with more of a ruin than a serviceable church.  Thus, what is highlighted by this paradox is that the function of the art object has to be balanced with the meaning we attribute to it.  And it is the charge of art conservation to strike this difficult balance, for how an art object was made and how it is used often come into direct conflict.  Being a conservator in the wake of this Ruskinian debate means navigating the nuances of this balance and knowing the difference between the meaning and practice of restoration and conservation.

¹Ruskin, John. The Seven Lamps of Architecture. 1849: pp.258-259

²Brooks, Chris.  The Gothic Revival. Phaidon: London, 1999, pp.303-305

³Miele, Chris. “The Gothic Revival and Gothic Architecture,” p.543.  Parlimentary Accounts and Papers, “Survey of Church Building and Restoration, 1840-1875,” v. 58 1876.

A painted replica of a c. 490 B.C.E. archer. For more information, and the source of this image, see the Smithsonian Magazine: http://www.smithsonianmag.com/arts-culture/true-colors.html

True Colors is an exhibition about polychromy in ancient Greek sculpture. Although we commonly think of stark white marble sculptures of Greek gods and goddesses as a signature of ancient Greek culture, these color-free statues were not the artists’ original intent. Before thousands of years of weathering and “cleaning,” these sculptures were brightly painted, almost garishly so. Scholars like archaeologist Dr. Vinzenz Brinkmann have been actively trying to correct the public’s misperception of ancient Greek sculpture. He has put together exhibitions at several museums in Europe and the U. S. that juxtapose original Greek statuary with painted replicas. The paint on the replicas is based on chemical analysis of trace amounts of paint discovered on the originals. When it came time to propose an exhibition for class that would creatively blend concepts in art and chemistry, the polychromy of ancient Greek sculpture was a great topic to choose.

One of the authors of the winning proposal, Ivy, is spending her summer preparing for the exhibition. Ivy just finished her freshman year at Stanford and is pursuing a degree in chemical engineering. Her chemistry background will come in handy as she attempts to analyze a Greek sculpture from the Cantor Arts Center’s collection for traces of pigments. She plans to conduct this analysis on campus with the help and expertise found in various scientific departments. After she has identified some of the original colors of the sculpture, she will use a 3D scanner to create a 3D CAD file of the sculpture. This will allow her to use rapid prototyping to create two replicas. The first replica she will paint with the pigments she identified on the original. Because the pigments she finds will likely be insufficient to provide enough pigment data to paint the whole sculpture, a second replica will be painted based on an educated guess of what the original work looked like. Ivy has an exciting summer ahead of her and will be making some of her own posts about her progress.

A portrait of Roman emperor Caligula and a color reconstruction by Brinkmann.

By Dave Evans

Stanford University is chock full of resources and enterprising individuals, making it an ideal place to solve unique problems.  So when Cantor Arts Center wanted to find a better way to cover up the exposed ends of a totem pole, they were right in believing that someone on campus could help.

In order to accomplish this, the museum contacted the University’s Product Realization Lab (PRL)—part of the Mechanical Engineering Department.   The Associate Director of the PRL, Craig, first discussed the project with museum staff and then proposed it to me and my fellow graduate students.  It piqued my interest as well as my friend John’s and just like that the project had a design and fabrication team. Because of our passion for woodworking and the outdoors, when presented with the opportunity to assist in the repair of Northwest Coast totem pole, we both happily volunteered to lend a hand.

We were tasked with finding a way to keep water out of the wood and prevent both rotting and splitting in high-risk areas. This meant finding a way to protect the wing tenons and exposed endgrain on the tops of the uppermost portions. Each area had its own issues to address.

Problem Area 1: The Wing Tenons

The wings are attached to the body of the totem with mortise-and-tenon joints.  Unfortunately the angle at which the wings are attached causes them to act like rain gutters, funneling water down the wing and directly into the mortises. In the below picture you can see the sediment left over from the pooling water at the edge of the mortise-tenon joint. That’s not good for the wood at all!  This problem is now doubly important as the totem has an epoxy-lined, watertight mortise joint that will retain water even more effectively.

Problem Area 2: Exposed End Grain

The heads of the thunderbird (the top most carving) and raven (the figure directly below it) have large areas of exposed cedar end grain. Water easily enters the wood here, resulting in expansion and contraction and leading to splits and checks. The exposed end grain is also more vulnerable to fungal growth and decomposition than the closed sides of the totem pole.

Museum staff had already consulted totem pole restoration experts to give us a head start. They had ascertained that the generally accepted solution to these common problems is to shield the water afflicted areas with with sheetmetal, occasionally supplementing their application with a non-permanent sealant.

After discussing various other options with Cantor Arts Center staff (covering a totem pole in epoxy is unacceptable), we climbed the scaffolding surrounding Boo-Qwilla to assess the situation and consider exactly how to proceed.  While larger more protective coverings were discussed, the smallest design that remained effective was chosen.  The Center wanted to keep the totem as safe as possible without adding any visual distractions. Soon a design direction had been established and it was time to get physical.

Getting sheetmetal to fit the hand-carved curves of Boo-Qwilla is no easy task, particularly because the fit needed to be excellent to keep water out of vulnerable spots. (To further emphasize the point, the top of the pole had been covered since the beginning with an ill-fitting piece of galvanized steel, to little obvious effect.)

The Design School at Stanford encourages using rapidly build prototypes and mockups to speed along the process of finding a solution.  The designs started off as simple mockups in Photoshop to explore possibilities. Once a general direction was established, we climbed the scaffolding with large sheets of cardstock, scissors, and tape. Paper folds and shapes surprisingly like sheetmetal does, but it adds the benefits of being cheap, simple to work with, and easy to modify quickly. Perhaps most importantly, paper won’t damage the soft red cedar when test pieces are still ill-fitting.

Eventually, after numerous trips up the scaffolding with ever-refining paper templates in hand, the fit was perfected and was approved by the museum’s staff.   The paper templates were then duplicated in sheet lead. Since the amount of lead we needed was negligible and it was to be installed far out of public reach, Stanford’s Environmental Health & Safety department gave us the go ahead.  When rainwater runs off the new flashing it will carry a miniscule amount of the metal with it, covering the totem with a small amount of lead and creating an inhospitable habitat for fungi and pests.

Lead is a marvelous material, though much maligned. It shapes even more easily than paper, is soft enough to be worked by hand, and develops a nice dull patina that will minimize visual obtrusiveness. Because the metal is also dense and heavy, it is less vulnerable to high winds or squirrel theft. Lead is relatively safe to work with too, as long as it’s not sanded into dust it can safely be worked by gloved hands.

Solution1: Shielding the Tenons and Rerouting the Runoff

Preventing rainwater from entering the mortise requires the paths of ingress to be covered while the rainwater is channeled off the wing to prevent pooling. To keep the solution as minimalist as possible, triangular caps were sealed in place to suit both tasks.

First, the caps are large enough to cover the entire area above and around the mortises. Second, the edge of the cap that runs along the tenon needed to be angled in a way that pushed the water off the edge of the wing, rather than pooling at thunderbird’s shoulders. After a bit of analysis, an oblique angle was found that would result in a net-downhill path off the tenon. With the cap sealed along this line water rolls harmlessly off the back of the wing’s tenon.

Solution 2: Capping the End Grain

Lead caps were fit for the two largest end grain surfaces on Boo-Qwilla: the heads of thunderbird and raven. Covering thunderbird is relatively easy since the cap has little curvature and a simple outline. Covering raven is considerably more difficult because, well, thunderbird is standing on its head. The cap must be fit around thunderbird’s feet in two relatively complex pieces. Here it’s especially important that the tricky, iterative refinement of the cap forms is done in paper to avoid dinging or scratching the soft cedar.

All of the lead caps are cut so that the water will run off the endgrain surfaces at steep angles where possible. If pieces must overlap they are designed to be “shingled”, ensuring that water running off one piece will continue running off the other.

Beads of non-permanent, non-skinning butyl caulk were laid down about one inch in from the edges that would benefit from additional sealing. (i.e. those that are most exposed to the elements) As in any restoration project, reversibility is a much coveted characteristic and the long tack-life of this product could become important if the flashing needs to be removed some time in the future.  Once each piece was fit, they were screwed down to prevent shifting. Due to the possibility of galvanic corrosion between the steel screw and the lead sheet, nylon washers were used to separate the two.  Moreover, Western Red Cedar (Thuja plicata) is highly acidic and would corrode galvanized steel screws at an accelerated rate.  Because of this stainless steel fasteners were used and their heads were painted to match the matte gray of the lead.

Each piece of lead had its edges left slightly oversized so a final trim could be done in place, thus ensuring a perfect fit. Then, the custom lead covers were filed smooth before their edges were gently rolled with a leather mallet. Rolling the edges of the lead ensures that the vulnerable ends are completely protected from water and insect ingress. Rolled edges also increase the strength, rigidity, and filtering of the sheetmetal pieces for structural purposes.

Ultimately seven separate pieces of metal were cut, formed, sealed, and screwed to Boo-Qwilla: a hat and a pair of two-piece shoulder pads for thunderbird, and a two piece hat for raven. It took weeks and weeks of paper test fits, discussions, material planning sessions, and sheetmetal forming to get the parts just right. Hopefully, all the planning and effort will result in no one ever noticing the change. All in all, for a pair of guys who consider themselves engineers, designers, and craftsmen, that’s a job well done.