APT DC Blog
Kimberly Robinson, Museum Curator with the National Park Service, and Bryan Fisher, AIA, Historic Preservation Specialist at GWWO Architects guided two groups of APT DC and AIA DC members and guests through Arlington House, The Robert E. Lee Memorial, to provide an overview of preservation and rehabilitation efforts slated for construction beginning this spring and extending into next year. The project includes the restoration of the mansion house, dependencies, and grounds as well as the construction of a new structure to support the visitor experience.
On February 24th APT DC took over Open Works in downtown Baltimore to learn about new and different digital fabrication techniques. The following are just a few takeaways from each of the wonderful speakers:
Jordan Greco from Xometry, Inc. "3D printing Technologies and Applications"
· 3D printing can be used for both inexpensive rapid prototyping (to test ideas) and manufacturing processes (to create jigs/one-offs)
· Many museums/collections now using 3D printing to create copies of artifacts for display
· Several types of 3D printing:
o Selective Laser Sintering (SLS) - allows a high level of complexity in the object
o Fused Deposition Modeling (FDM) - most common type of 3D printing, but not good for small details
o Stereolithography (SLA) and Polyjet (PJ3D) - Good surface finish, but not durable; can print in a variety of materials
o Direct Metal Laser Sintering (DMLS) - Prints using a fine metal powder; requires more intensive safety equipment
Joe Nicoli from Direct Dimensions "Digital Restoration"
· Many types of laser scanners available to scan everything from a landscape to a building to a small object
· From the scan, can create 3D models that can be scaled to any size
· Have used SLS 3D printing before to create building elements that have been installed (like a ceiling medallion) or for reference for the artisan's use
· When scanning an element for restoration, they often use their 3D artists to "restore" the scanned model element and manipulate the 3D model to match the original design intent
Sean Wise from Repliform, Inc. "Tangible Artifacts from Electroplated 3D Printed Parts"
· 3D printed objects can be electroplated to make them durable, strong, and less flammable
· This is particularly useful when creating replicas of artifacts and/or when creating visually accessible exhibit designs
· Electroplating can also be used to add cosmetic finishes to 3D printed designs
Thank you to all of our speakers and Open Works for hosting and giving us a tour!
Audrey Tepper, a Historic Architect with the National Park Service at the National Mall and Memorial Parks, and Tim Vandewalle, Superintendent at the Christman Company, both discussed their current and ongoing preservation efforts at some of our Nation's significant monuments at the Octagon House to a sold-out audience. Both presenters discussed the innovative technologies developed to appropriately restore and repair historic materials at National Monuments that spawned an informative Q&A discussion afterwards.
Our major takeaways from the presentations are as follows:
1. Increasing annual visitation numbers to our National Monuments are putting stress on our current historic resources. Aging visitor spaces need to be upgraded and many monuments are in need of restoration.
2. The aggressive bio-film found on the Thomas Jefferson Memorial has a unique biology, even different from a similar bio-film found across the Potomac at Arlington Cemetery.
3. Laser-cleaning was determined to be the only long-lasting solution for keeping the aggressive bio-film from growing back.
4. There are 4 methods of repairing cracked cast-iron
1. Heat (1000-1500 degrees Fahrenheit and is only successful when employed at corners of cast-iron)
4. In-kind Replacement
5. Lock-n-Stitch (a mechanical technique developed by Gary Reed) was chosen for the restoration of the Capitol Dome because it preserved the most material in-place among other significant reasons including limited heating processes to the already delicate historic cast iron.
6. Lock-n-Stitch developed a unique mechanical fastener for use on the Capitol Dome, which had a special profile to provide added strength to the low thread strength of in-place historic cast-iron.
7. Selective demolition and fit-up prior to commencement of cast-iron work is critical to the success of repairs.
8. Employ "magnetic particle inspection" after repairs have been completed to ensure no new cracks or discontinuities were formed.
9. Previous mid-century repairs to the Capitol Dome included heat-based repairs, which are irreversible and cannot be reworked or reheated.
Thanks to Kara Johnston for compiling these pointers and thank you to our presenters, we truly enjoyed learning about your experiences with our National Monuments!
Recently a small group of APT DC members were led on a tour of the exterior of the Sidney Yates building by representatives from Grunley Construction Company. The tour included discussions on the restoration techniques used at the windows and masonry units, and up-close viewing of these elements from the scaffolding at the south side and west sides of the building. A few key points from the project shared by Nick Patrick of Grunley include:
· 2 year project
· 130,000 LF of pointing (largest lime putty based repointing job in GSA’s building stock)
· Over 6400 brick replacements
· Over 1000 Jahn patches
· Over 60 new granite, bluestone, and brownstone stone replacements
· 1200 LF of new gutter installed
· Over 8000 LF of new flashing installed
· 568 windows restored
Thanks go out to Grunley for sharing the project with APT DC!
Moira Nadal, one of this year's recipients of APT DC's Emerging Professionals Sponsorships, attended the 2017 APTI Conference in Ottawa, Ontario. The following is her summary of the workshop.
I was thrilled to receive the scholarship to attend the APT-National Trust of Canada joint conference in Ottawa. Since I work for the National Trust in the United States (NTHP) I was interested to see the types of programming put on by the National Trust of Canada and how it was joined with the technical presentations from APT. There seemed to be two main points of focus for the conference; indigenous heritage and sustainability.
The conference was organized along the following tracks: Documentation and Diagnostics – Understanding Historic Places; Design – Planning the Conservation of Historic Places; Delivery – Intervening in Historic Places; Policy and Practice; Canada 150 – Indigenous Heritage, Diversity, and New Directions; Integrating Old and New – Buildings, Districts, and Landscapes; and Regeneration – Community, Economics, and Equitable Places. I attended a variety of sessions, some technical and some cultural. As some of the presentations were in French, the other national language of Canada, we were provided with headphones connected to simultaneous interpreters. It was very cool and made me feel like I was at the UN.
Several session topics were helpful for potential reviews that I may have to conduct for my position with NTHP. I learned about base isolation for seismic retrofitting of historic buildings, which is immediately useful as I monitor properties in California and Oregon. There were also several presentations where I learned more about testing historic windows in situ to demonstrate their performance under specific conditions and with different modifications to make informed comparisons of retention versus replacement. After having the opportunity to walk around the historic district near the conference hotel, I also appreciated getting to know more about Parliament Hill and the ongoing work at that complex of buildings.
In addition to the presentation panels, there was a very full demonstration hall. It was so valuable to be able to ask questions of the vendors on site and helped me to understand some of the newer products and methodologies I’ve been hearing about. I especially enjoyed the hands-on demonstrations by students from the Heritage Institute of Algonquin College. We shared desserts from the reception while planing molding profiles. Overall, the conference was a great mix of detailed technical presentations, larger cultural and theoretical discussions, and networking with professionals from throughout North America and 20 represented nations.
Naomi Doddington, one of this year's recipient of APTDC's Emerging Professional Sponsorship, attended IPTN's 2017 workshop in Detroit. The following is her summary of the workshop.
The Preservation Trades Network’s annual conference, the International Preservation Trades Workshop, was held in Detroit this year. I was honored to receive the 2017 APT DC Emerging Professional Scholarship Program scholarship to attend the conference this year. IPTW consists of 2 ½ days of hands-on workshops where participants are able to interact with experts in different preservation trades.
Our host location this year was the Belle Isle Boat House, a once-magnificent club house that still serves as home base for a local rowing team…and was the site of the Olympic swim trials where Johnny Weissmuller, who would go on to play Tarzan in the 30s and 40s, qualified for the games. Upkeep on this site has suffered with the decline of private-club membership and some well-intentioned, yet ultimately destructive, maintenance decisions in the early 2000’s. This includes the use of a strong Portland cement stucco to cover the exterior, exacerbating an existing moisture problem that has caused significant rust-jacking of structural steel within the brick walls.
As part of its conference, some IPTW presenters utilize their skills to provide free work on the host site while they teach attendees about their work. In this photo, presenter Blair Bates discusses the process of repairing the stucco on the exterior of the building. The stucco applied in the 2000’s, with a high concentration of Portland cement, has already started to fail in certain places. Blair had been on site for a few days and had removed the unsound stucco from above a window near the entrance. He explained how he was using type “K” mortar mix for the new stucco. This mix is 1 part white Portland cement, 3 parts lime and 10 parts mason’s sand. This is a very soft, low-compression mix useful in this type of application. Horsehair not being as readily available as it once was, Blair has been using nylon fibers in the mix in its place. There are two main things I learned from Blair’s presentation. When using a float to smooth the surface of the stucco, Blair recommends holding it in your non-dominant hand and pull the float towards your body. In this manner, you are less likely to put too much pressure on the stucco in any given place. The second is a fun bit of trivia that could be useful sometime. The different mortar mixes are assigned every other letter of the phrase, “MASON WORK”. Additionally, you can tell the proportion of cement to lime in the mix based on its position within the word. “M” mix is 3 parts cement to 1 part lime. “S” is 2 parts cement to 1 part lime. “N” is 1 to 1. “O” is 1 part cement to 2 parts lime. Finally, “K” is the 1:3 mix as described above.
You may know that producing shellac involves beetles, but did you know how? I had always assumed we were pulverizing the little bugs and mixing it with a solvent to create the shiny topcoat (you know, like red food dye). In fact, the bugs are not sacrificed at all! The lac beetle sucks the sap out of a tree, then excretes the digested results in tunnels on the exterior of the tree. This sap/poo is scraped off the trees, processed, dried, and crumbled up. When mixed with denatured alcohol (or moonshine), it creates the high-gloss finish we associate with shellac. The color of the shellac is actually dependent on the type of tree that the beetles were extracting sap from. Mary Webb, of the National Parks Service Western Archaeological and Conservation Center gave a great presentation on environmentally friendly(er) finishes for wood as well as the best pro-environment ways to remove old finishes. As you can imagine, my fellow preservationists, older techniques are generally less toxic than the 20th century paints and stains that we have to so often protect ourselves from when we work in our treasured buildings. Long live linseed oil!
There were several presentations on windows. Andrea Sevonty and her employees had dismantled the one stained glass window in the club and were re-making the piece. She greatly lamented that poor solder work (especially previous amateur repair efforts) had required re-making the window as the cames themselves had been in good shape. The crew had traced the window while still intact and was using this as a guide to the reassembly, with each piece of carefully labeled glass corresponding to a number on the cartoon. Andrea explained the easy test to tell if the cames (those are the metal pieces between each piece of glass) are lead or zinc. Using your fingernail, try to scratch the came. If you are successful, then you know the came is lead. If not, it is the harder zinc. You may think that with a design comprised of mainly clear glass, replacing broken pieces would be a breeze. Andrea actually explained it can be rather tricky as “clear” glass can skew pink, purple, or even yellow depending on the makeup of the glass! Kevin Doenir and his crew from the Window Preservation Alliance spent their time repairing a pair of round clerestory windows from the Boat House’s beautiful double-height main hall. I’ve done a fair bit of window work in my day, but I did learn a neat trick. This works well when working on a window you’ve removed from its opening. After glazing with a linseed oil based putty, sprinkle a little bit of whiting in the center of the glass pane. Using a dry brush, swirl the whiting all around the pane, working from the center out to the edges. This removes any last vestiges of oil from the center of the glass, resulting in sparkling window panes ready for paint and reinstallation!
Is Bob insane? This is real knob and tube lighting…and he has his finger in the socket (after licking it first no less)! Not according to Peter Janko. Although Peter explained that knob and tube is not inherently dangerous, it runs so counter to what we all understand of electricity. It does generate a fair bit of heat, which is meant to dissipate into the air around the wires (thus why it is held at a remove from the surface). Only when we insisted on insulating with cellulose did we create a problem. By surrounding the wire with cellulose, we forced the heat to dissipate into a highly flammable material. Even so, Peter has discovered a way to use existing knob and tube, or even install a new system, and still meet code. The secret lies in LED technology. If you come across a system that is still wired, you can disconnect any wire that runs to a plug (they do overheat badly and won’t pass code), connect the system to a low voltage source (four E batteries for the example where our volunteer stuck his wet finger in the socket…and you can see how bright the bulb next to it is lit) and special low-voltage LED bulbs. He has had success using this system in new construction by calling it “Decorative Low-Voltage LED Lighting”. You can even buy a 12v battery (often used as backup power for a computer) to run your system. Simply buy a battery maintainer (like for a snowmobile) to recharge your battery periodically and you’ll have a power-outage proof system.
Sharpening tools is vital to many trades. Rudy Christian presented his preferred method for sharpening tools. He began with a humble chisel. Starting with a water bath wet-stone grinder with a 250 grit wheel, Rudy laid the primary bevel (the big angle you picture when you think of a chisel) against the spinning wheel, allowing it to remove just a sliver of the metal. With a 250 grit waterstone (kept in his cooler full of water), Randy then manually smoothed the high spots left by the machine. He moved on to an 800 grit waterstone next, making sure that the primary bevel was flat against each stone on every pull. Then he did something I never knew to do. He pulled out a 3,000 grit diamond waterstone (it looks a bit like a waffle iron griddle) and laid the chisel’s primary bevel against the surface. Before pulling the chisel towards his body he lifted the chisel up just 5%. In this way, he put a micro-bevel on the very tip of his chisel. This micro-bevel helps to move the wood away from the main bevel, allowing for faster and neater work.
I’ve saved the best for last! I’ve done a fair bit of decorative finishing in my day. Wood graining, marbling, Venetian plaster, I was intrigued to learn there was a technique I had never even heard of. This is the Italian technique called Scagliola. Mixing gypsum plaster, powdered pigment, and water with glue (to slow the plaster setting), scagliola replicates the look of marble in a time-consuming, but less expensive, manner. You are also limited only by your imagination as to the color and color-combinations that you want to use. I actually attended two sessions on this technique. The first was a hands-on presentation where I got to work with other attendees to mix balls of this plaster, cutting and mixing them with others to create a gradation of colors from blue to teal. We cut these balls into smaller pieces, then laid them randomly on a greased form (we were making a bowl) then pushed and smoothed the colors together to form a consistent thickness over the mold. Using a putty knife, David Hayles, our fearless instructor, cut veins into the plaster. We filled these with a yellow-ochre batch of the same plaster mix then smoothed the veins closed. Finally, David cut another set of veins and we filled them with a deep brown plaster mix. With lots and lots and lots and lots of sanding, our bowl will look somewhat like the one in the photograph. The second scagliola session I attended was David showcasing how a similar technique is used to decorate a column. This involves raw silk thread, very liquid plaster, Pollock-inspired application, and a joie de vivre that is infectious.
Seeing the end-results of some of the presentations was a lot of fun as well. I got to see stone carvings that were amazingly intricate and plaster pieces that were massive! I also visited blacksmith Owen C Creteau, Jr. and encountered a few pieces he has forged that puzzled me. The first were some amazing puzzles he has forged out of nails and other small metal pieces. The second was larger piece he had arranged on a table with the candlesticks, fire pokers, and other more readily-identified pieces. I puzzled over it for a few minutes before finally breaking down and asking him. It turns out, this is a toaster. One puts pieces of bread in the middle, then uses the handle to place the whole apparatus on the hearth close to the fire. Once one side is toasted, the piece is lifted by the handle and turned so that the other side is close to the fire. Ingenious!
The International Preservation Trades Workshop was a great deal of fun and a source of inspiration to me as a preservationist. I was able to close my weekend by giving back. The National Trust happened to be holding a work day at nearby Fort Wayne. Like many formerly active military installations around the country, Fort Wayne has facilities that span more than a century of construction techniques and had been badly neglected before being turned over to the city as a park. Throughout the day Sunday, more than 300 volunteers scraped and painted wood porches, built protective coverings for vulnerable building fabric, and re-glazed (in place) dozens of windows on former officer’s quarters. I participated in the latter and, I hope, we bought these historic materials a few more years as further funds are raised to do more.
At the 2017 APT DC Symposium this May, over 90 preservation professionals from a variety of backgrounds gathered to hear from experts working to increase energy efficiency in historic structures. The day’s presentations covered energy codes, energy models, increasing the efficiency of historic materials, and regional case studies. The day opened with a presentation from Historic Environment Scotland, demonstrating that the desire for efficiency in our historic resources is global!
Our top ten takeaways from the Symposium are:
1. International standards like the IgCC set a minimum baseline for energy codes, but codes can vary widely by local jurisdiction. Using an integrated design process and working with local code officials will ensure you are following the right directives for your structure and locality.
2. Energy standards like LEED, ENERGY STAR, and others provide guidance in achieving a high level of energy efficiency for your structure.
3. Achieving energy savings with historic preservation projects is well within reach, even though improvements to the envelope often aren’t feasible. Using energy models will help you determine improvements that provide the biggest savings for the lowest impact.
4. There are many types of energy models available on the market. Using the right model at the right time will help you predict or assess energy savings before, during, and after a project.
5. Think carefully about which components in your building are most appropriate for upgrades or modifications:
6. Energy modeling can show the order-of-magnitude effect of different upgrades to a Modernist curtain wall-clad building’s systems to help owners decide in which upgrades they would like to invest in (mechanical, lighting, enclosure, etc.).
7. Mass masonry walls are prone to deterioration if insulated improperly. It’s important to use tools like hygrothermal analysis to determine the brick’s properties and select the right type of insulating material.
8. New technologies like interior window retrofits will allow for greater insulation of historic sites without compromising original glazing materials or character.
9. Before inserting new materials into an existing system, make sure to investigate how your building and its materials are designed to perform, and consider how modifying an existing system will affect the structure. Investigate the real cause of problems first - maintenance issues, leaks, improper flashing, failure of finishes, etc.
10. There are many reasons to pursue energy efficiency in a historic preservation project: cost savings, occupant comfort, material preservation, and of course, environmental impact. Local programs like Sustainable DC recognize that historic resources are often most at risk for the effects of climate change. We all have a part to play in ensuring the worst consequences don’t come to reality!
We’re so thankful to all our presenters for sharing their work with our audience! If you are interested in learning more, PDFs of their presentations have been made available on the APT DC Symposium web page. Thanks also to the sponsors who made the event possible: Encore Sustainable Design; The Weidt Group; Conservation Solutions, Inc; Quinn Evans Architects; EHT Traceries; Consigli Construction; and our host, the Fred W. Smith Library for the Study of George Washington at Mount Vernon.
Welcome to Preservation Pointers, APT DC’s new blog series! Here, we will post about events, tours, and lectures hosted by APT DC. The blog will summarize the important points from those events which we feel are the most useful to preservation professionals.
Preservation Pointers #1: Takeaways from APT DC’s April Tour of Cathedral Stone
Cathedral Stone, Inc., manufacturer of specialty cleaning products, paint strippers, and repair mortars for masonry, hosted a tour and hands-on learning experience for APT DC on Saturday, April 22, 2017 at their manufacturing facility. The following topics were discussed.
There are several different categories of cleaning products available to preservation professionals for use on masonry. It is important to understand the proper uses and application for each, and to always test cleaners prior to full application. Some of the most common types of cleaners on the market are:
As the preservation industry moves away from solvent-based paint strippers due to health and environmental concerns, more water-based products are becoming available. Water-based paint strippers have the following advantages:
Failures in masonry restoration often result from patching materials that are stronger than the stone substrate. It is critical that patching materials have a lower compressive strength the substrate itself. Porous stone substrates also need to be able to breathe. Patching materials that have low water vapor permeability entrap moisture within the stone, leading to failure. Polymers, which are often used as an adhesive agent to form a strong bond with the substrate, can eventually lead to failure by trapping water and salts. They also tend to discolor over time because they are not UV stable.
When selecting a patching mortar, it is critical to select a material that is colored with UV stable pigments that will not fade out. It is also important to recognize the effect of the amount of mixing water on the color of the cured mortar. When evaluating mortar samples for color, they should always be applied on a proper substrate. The practice of creating mortar samples in coffee cups, common among some masonry contractors, doesn’t give a true representation of color because water is not allowed to evaporate through the Styrofoam or plastic. Instead, samples should be placed on a porous substrate, ideally the same substrate where mortar will be applied.
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