Equipment choices for Visible Induced Infrared Luminescence

by Tessa de Alarcon

Since we have posted often about visible induced infrared luminescence (VIL) and the equipment we use at the Penn Museum, we on occasion get emails from other conservators and museum professionals asking about what equipment to buy and the costs associated with this photographic technique. This technique is often used for imaging Egyptian blue, but it can also be used for Han blue and Han purple. Much of the same equipment is also used for infrared reflectance.

E1827A-E multimodal data set including a visible image (left) and infrared reflectance image (center) and a visible induced infrared luminescence image (right).

Making specific equipment recommendations though are tough because there are a lot of options and a lot depends on your budget. Basically though, what you need are the right lights, a camera (and lens), and a long pass filter for the camera to capture in the infrared. I thought I’d do some testing to show how some these different elements impact the results in the hopes that it might help others figure out budgets, and to show that it’s also possible to build this equipment up piece meal, starting with equipment you might already have or is very low cost. Some elements though are pricey and things can add up.

All of the VIL images in this blog post also have a Spectralon standard in them (99% infrared reflectance standard). This is not low cost, and not required for the technique. It is often required for publication, and is useful for trouble shooting or developing new techniques. I’m mentioning this because it is useful to evaluate the data presented here, but it isn’t something that is strictly required. We did not have one for a long time, but were able to do this type of imaging. We waited as it was a big investment for us (approx. $500). These standards also range in price depending on the size and calibration.

An infrared (IR) filter is a requirement for this technique. I only tested one IR filter (though we have two). They range in cost depending on where you get it and the quality of the filer and the size of the filter. Ours is a B+W and is an 830nm IR long pass filter and is 62mm ($130). There are cheaper ones available as well as more expensive ones too. We got ours to fit our macro lens, and have adaptor rings (all our rings are generic brand low cost ones that were each under $10) to fit it onto other lenses that we have.

The right lights are a critical factor for this technique, but not necessarily one that has be high cost. You need a bright light with no infrared radiation, red lights are commonly used and LED bulbs are preferred as they produce no infrared radiation. I tested out three different lights for visible induced infrared luminesce. These include at the high end of the budget a Mega 64 Profile Plus RGB + UV Par light at maximum intensity with the red LEDs on only. This is a roughly $200 light. The other lights I tested are both low cost options. I tested one FEIT electric one red LED light bulb I put in one of our extra reflectors and photo light stands. I bought this bulb for $6 from my local hardware store, and a two daylight LED bulbs (UL certified) that I got from our facilities department to replace burnt out bulbs on our copy stand. I used both bulbs in the regular copy stand set up for imaging. I don’t know what the bulbs I got from facilities cost, but there are no brand name stamps on them so I’m guessing they weren’t expensive, that UL logo on it just means that it is a UL certified bulb.

The Mega 64 profile plus (left), a daylight LED bulb (center), and a red LED bulb (right)

I tried both our full spectrum modified camera, and our regular digital SLR (unmodified). Neither of these is an inexpensive camera, but should show generally the difference between using what ever digital camera you already have, and getting a similar cost one as a modified camera. Neither is new, we use our cameras until they can’t be repaired. The unmodified camera is a Nikon DSLR D5100 and the modified camera is a Nikon DSLR D5200. We bought our modified camera new, and sent it to Life Pixel to remove the internal filter, but they now sell used cameras that they will modify for you (there are options). Ours was modified to be a full spectrum camera. At the time of writing this post, the most economical option I saw on life pixel for a used camera with this modification package cost a total of $449. So even used not cheap. But lets get to the testing and start looking at results.

Lets get to the results from the modified camera. I have a visible reference image in the set, and the VIL images using each of the different lights. All the lights worked, but the brighter MEGA par 64 gave the best results, especially at exciting traces of Egyptian blue. Though the daylight no-name brand LED bulbs were not bad. These have a range of camera settings, and the benefit of the modified camera is that I could see the results in live view, focus the image and adjust the settings with minimal bracketing. The spectralon should not be visible, and if it is usually means that the image capture settings are not quiet right.

Modified Camera results: visible reference image (top left), VIL image with the MEGA 64 LED lights (top right), VIL image with the no-name daylight LED bulbs (bottom left), and VIL image with the RED LED bulb (bottom right).

Next up, the unmodified camera. The images are arranged in order of the lights used the same way as for the modified camera for easy comparison. So I did get results with all of the lights. The down side is that the live view shows nothing so the focus can’t be corrected. These images are all slightly out of focus because the focus in IR is different from the focus when capturing in the visible range and I focused the image before putting on the IR filter. All of them had to be taken at the longest possible exposure of 30 seconds. This made data collection easy since I had no choice in settings. And for the low costs bulbs it looked like they were just black with no data until I got them in adobe camera raw and converted them to grey scale by adjusting the saturation to -100. Then I could see something, but I did also adjust the exposure for the images you see here. You can see the spectralon and the background in all of the images and interpretation might be harder with these than the images taken with the modified camera. I will say I think this could be used for detecting Egyptian blue, but it’s important to note that the unmodified camera only got the thick areas of Egyptian blue, and didn’t have the sensitivity to pick up the traces visible in the images taken by the modified camera.

Unmodified Camera results: visible reference image (top left), VIL image with the MEGA 64 LED lights (top right), VIL image with the no-name daylight LED bulbs (bottom left), and VIL image with the RED LED bulb (bottom right).

For fun, I also tried putting the IR filter over my cell phone and using the MEGA par lights took a photo. This is just to show that even a small sensor like what is in a cell phone camera can work. It is out of focus though and like with the unmodified Nikon DSLR you aren’t getting traces of Egyptian blue. But it did show something, and I could see the results in the live view. This is also an avenue that I know others are working on: producing low cost modified cell phone cameras with built in filter wheels. Sean Billups has presented at AIC on this topic.

Cellphone VIL image: unprocessed and shown as shot with an 830nm IR long pass filter over a an unmodified cellphone camera

To wrap things up, I think it is possible to build this equipment up overtime. You can start with the camera you already have for documentation, and then get better lights and a camera as you can afford them. The IR filter can also be used for IR reflectance, this is also possible with any digital camera with a long exposure and using any light that produces infrared radiation. There is much less difference in data quality between a modified full spectrum camera and an unmodified camera for this method, though again there is no live view and sharp focus is hard to do with an unmodified camera. We use incandescent photo floods (real bright and toasty) but any light that gets warm probably produces infrared radiation and could be used. Daylight for example works real well too (and is free).

Infrared reflectance images (left) and infrared reflectance false color images (right). The modified full spectrum camera was used for the images on the top and the unmodified camera was used for the images on the bottom.

Caring For Culture: Introducing Teens to Museum Conservation

By Lu Denegre

All photos by Emily Hirshorn

On June 4th, 2022, with the help of funding from the Museum Council of Greater Philadelphia, the Conservation and Learning Programs departments hosted “Caring for Culture”, a hands-on introduction to conservation for teens. We had a great time and got some good feedback, and look forward to welcoming another group of teens this year on June 3rd 2023!

(If you’re a teen in the Philly area, you can register here for this year’s workshop)

Last year, 24 students arrived at the museum for a day of activities. The workshop began with introductions and a presentation by Senior Project Conservator Molly Gleeson about the basics of museum conservation. What kind of work does it involve? Why do we do it and what can damage cultural heritage collections?  

Molly Gleeson addresses Caring For Culture Participants in Widener Auditorium, and a diagram of the Agents of Deterioration (from A Guide to Risk Management of Cultural Heritage (p. 27), ICCROM, 2016).

Next, participants were led in smaller groups on a tour of the Museum’s conservation lab spaces by Head Conservator Lynn Grant. They got to see the X-Ray room, the photo studio, prep room, and main lab. Lynn and Graduate Intern Nylah Byrd spoke about the different treatments a large wall painting, a cartonnage mask, and a stone sculpture have undergone. These objects will be included in the upcoming reinstallation of the Ancient Egypt and Nubia Galleries and have collectively required different types of imaging, storage mounts, cleaning, and structural and aesthetic fills. 

Lynn Grant leads a tour of the conservation lab
Nylah Byrd talks about the treatment of a cartonnage mask

For rest of the morning, the groups were led into the galleries by a member of the conservation department to do some documentation of their own. Each participant chose an object in the galleries to condition report and diagram. Condition reporting is one of the first things you learn as a conservator and is the first important step in assessing an object’s needs before starting treatment. This activity offered opportunities to look for real life examples of condition issues, agents of deterioration, preventative conservation steps, and mountmaking.

Participants observing a strategy for a large fill on an object in the Middle East Gallery
Completing condition report worksheets for an object chosen in the galleries

After a sunny lunch in the Warden Garden, participants came back in for some hands-on activities. Groups rotated between three stations: cleaning, close looking, and ceramic reassembly. These stations introduced some of the beginning skills needed by a conservator in training. 

At the cleaning station, teens learned to roll their own cotton swabs to gently remove grime from the surface of a dirty tile. They also applied warm agar gel to learn how we loosen up and remove grime without using too much water on more sensitive objects or more stubborn dirt. 

A participant swab cleans a dirty tile

At the close looking station, teens used a Dino-lite digital microscope to get up close and personal with some study objects. A UV light setup showed that the way materials fluoresce differently under Ultra-Violet light can help identify unknown substances. 

Conservator Julia Commander guides participants through using a Dino-lite microscope

At the ceramic reassembly station, teams worked to puzzle out the correct location of sherds and reconstruct a ceramic object. Small sandboxes, blue tape, and clamps to hold everything in place are essential tools for gluing a ceramic back together. 

If students tried their hand at each table and still had time to spare, there were also individual activities on color matching and inpainting prepared for some down time. 

We were happy to see such enthusiastic attendance of this program last year and hope we get to meet some more future conservators at the workshop next month! If you or someone you know would like to participate, you can find more info and register here for this year’s workshop!

2D to 3D

By Chelsea Kim

As an intern working with the conservation department, I have received the opportunity to work on many projects and experience things I never thought I would. Recently I have been working on this software called Reality Capture using photogrammetry. Photogrammetry is a process that uses an abundance of photographs to create a 3D model without any distortion from many overlapping images stitched together to form a detailed and geometrically corrected image called an orthomosaic. This process is usually used on larger objects, and this is because it’s too big to be in frame when taking pictures and has a lower quality with distortion which is far from perfect, and Christy Ching explains more in depth about this in her previous blog post.

I want to show how to create a digital three-dimensional model using the software, Reality Capture, and I’ll demonstrate with an example of the after-treatment photos of an Egyptian coffin.

To start off with, having pictures of the object is a must. For this example, they were already taken and edited in Photoshop, to adjust the white balance using adobe bridge ahead of time. Then I begin by opening the software and then under workflow at the top left corner, I select “inputs.”

Screenshot of the software highlighting where to click “Inputs” which is above “1. Add Imagery”

Then I select all the images making sure that they were a .jpeg file and then I click on “Align Images” as highlighted above. After the images are aligned, a transparent box surrounding the coffin appears. I adjust the box by dragging the control points around to make it as small as possible without cutting off any part of the coffin. As you can see in the image below, using E883C, the box is close to the coffin but does not intercept the coffin itself.

Screenshot of the Egyptian coffin E883C after the images were aligned with the transparent box adjusted to tightly around it.

Now for the fun part to see the coffin take shape, I click next to “Calculate Model” to select “Preview Quality” as highlighted below. Then I go to the tools bar to use the lasso option to erase all the unnecessary space around the coffin. Then after being satisfied with selected area, I click on “Filter Selection,” which turns the selected areas from orange to dark blue showing that it worked.

Screenshot of the coffin after selecting “Preview Quality.”

Finally, I go back to the Workflow bar to select “Texture” which is highlighted below and then it shows all the details of the 3D model without any distortion in high detail and quality.

Screenshot of the 3D model after being textured.

Laser training for our monumental projects team

Our department has owned a Compact Phoenix Nd:YAG laser for several years now and we have successfully used it to clean objects like this trio of birds for our Middle East Galleries. While there are a lot of possible applications, we have found the laser to be especially effective for cleaning stone objects with coatings, stains, and surface grime that are not easily removed using other tried and true cleaning methods including solvents, steam, and gels.

Did somebody say “stone objects with coatings, stains, and surface grime”? Because we have tons of those (literally) in our Conservation Lab Annex (CLA) where we are working on monumental projects for the Ancient Egypt and Nubia Galleries. But the last time we held a laser training session was before we hired our CLA team. Lasers are not found in all conservation labs, so it is not unusual for experienced conservators to have little to no experience with lasers.

A small Egyptian limestone stela mid-treatment. Many cleaning tests were carried out on this piece with very little success in removing some of the grime and stains. It is a good candidate for some laser cleaning tests.

In order to ensure a safe set-up and to get everyone trained on the equipment, we brought in Philadelphia-based conservator Adam Jenkins to provide the team with a full day of training. Adam specializes in laser cleaning and also conducted our last training session at the Museum in 2017.

Adam demonstrating use of the laser

After a classroom session covering the fundamentals and science of lasers, and the necessary safety protocols and PPE, we moved to the lab to try the laser on a few objects. We had success with several, which is very promising! The team is now set up to continue laser testing and cleaning on their own. We are grateful to Adam for his expertise and support and for this professional development opportunity. We are excited to incorporate this tool into the work out at CLA!

CLA conservation technician Kyle Norris testing the laser on an Egyptian stela

The right tools for the (monumental) job

Greetings from the Penn Museum’s Conservation Lab Annex (CLA)! You may remember from our first post the scale (large!) and types of objects we are going to be working on over the next few years. We are mostly working on architectural elements like doorways, windows, and columns that were part of the palace complex of the Pharaoh Merenptah, who ruled Egypt from Memphis from 1213–1203 BC. To put things in perspective, the doorway we are currently working on is over 12 ft tall and many of its fragments weigh hundreds of pounds. That means we have had to add a few new tools that are not typically found in a museum’s conservation lab. Most recently we’ve started utilizing a lot of new tools including a forklift, a gantry, and large-scale sandboxes.  

  • Forklift – A few weeks ago, the whole Ancient Egypt and Nubia Galleries Team attended a certification workshop in forklift operation. The certification course taught us the basics in how to safely operate our electric forklift. Having our own forklift onsite allows us to easily move some of the large stone fragments in and out of the lab, reorganize the layout of the warehouse to create space for rigging and lifting, and organize all of the Merenptah Palace pieces into one area.   
Egyptian Section Curator Dr. Jennifer Wegner smoothly maneuvering the forklift during our training session.
  • Gantry – At CLA we have a gantry crane in the warehouse which allows us to rig and lift some of the heaviest objects and fragments. This is especially important when we are trying to dry-fit pieces together before making more permanent joins. There are lots of different ways to rig or strap a fragment for lifting, but we’ve found that using shorter straps with a choke hitch is the safest way to lift our artifacts. In the photo below you can see that’s exactly what we’ve done. Once we have the straps secured and fully supporting the object, we begin to slowly lift, making sure the straps settle and don’t slip or re-adjust, dropping the object.  
CLA team using the gantry to lift part of the lintel from Doorway 1.
  • Sandbox – Sandboxes are often used in conservation to support objects during joining. Using a sandbox, we can place an object inside at whatever angle we need to in order to support the object on top with nothing but the weight of gravity. At CLA, our objects are quite large, so we are using old shipping crates and converting them into large sandboxes to accommodate our needs. In the photos below you can see the process of moving a fragment into the sandbox and then in the second photo you can see that fragment has been placed in such a way that it can now support the weight of the second, joining fragment on top of it. The blue tape serves as a guide to help us know exactly how the two pieces fit together once we have applied the adhesive and are ready to do the final joining. 
CLA team moving part of the lintel from Doorway 1 into a sandbox.
Fragments of Doorway 1 lintel being dry-fit together in the sandbox prior to joining.
  • Dremel – Lastly, and on a much smaller scale, we’ve been using a few different power tools. The most helpful so far has been the Dremel. While the Dremel is not a completely foreign tool to many conservators, it is most often used for making mounts or sanding fills and/or cross-sections. In this case we are using the Dremel to cut and remove all restoration pins that have become heavily corroded over the years, expanded, and are causing damage to the stone.   
Corroded ferrous pins from a previous restoration being cut and removed from Doorway 1 fragments.

As with any job, having the right tools is really important, for success and safety! We look forward to continuing to share the progress we’ve made on this project from our home offices, as we continue to work from home.

Cross-Campus Conservation Collaboration!

by Adrienne Gendron

Professional conservators generally specialize by material type. All the conservators at the Penn Museum specialize in objects, which includes a wide variety of materials from stone and ceramics to leather and wood. However, occasionally materials come across our desks that fall outside our areas of expertise. The Penn Museum recently acquired twelve Indian paintings on paper which need to be hinged so they can be safely handled by researchers. Because paper is a separate sub-specialty of conservation, we called on our friends at the Steven Miller Conservation Lab at the Penn Libraries’ Kislak Center for Special Collections, Rare Books and Manuscripts to help us with this task. This is not the first time we have taken advantage of our book and paper conservation colleagues right here on campus – follow this link to read about a recent treatment carried out in their labs on a parchment scroll.

In the case of the hinging project, our Penn Libraries conservation colleagues came to us – a couple weeks ago, Elizabeth McDermott, Tessa Gadomski, and Sarah Reidell visited our lab to provide a workshop on how to properly hinge paper objects for display.

Penn Museum conservators and interns listening to Liz and Tessa give instruction.

Hinging is a process in which small strips of paper are carefully adhered to the back of a work of art on paper in order to secure it within a window mat. It results in a strong and secure housing solution that ensures the safety of the object for storage and display.

One of the twelve works on paper that needs to be hinged (2017-22-13).

The most common and secure method of hinging is called a T hinge, which is composed of two strips of Japanese tissue paper. First, a strip of paper is carefully cut to size and a small amount of reversible adhesive is applied. Then, the strip is applied to the back of the top edge of the work and allowed to dry under weights.

The first strips in place along the top edge of a sample object.

Next, the work is flipped face-up and positioned on its backing mat. This is the trickiest part of the process, as the work must be perfectly positioned so that when the window mat is closed, it appears centered. Then, a second strip is adhered over the first strip and onto the backing board to secure the work in place.

The second strips applied over the first strips and onto the backing board, securing the work in place.

Because conservation is a small field, people often call on colleagues to for advice when it comes to different areas of expertise. We’re excited to apply our new skill to the twelve Indian paintings to ensure their long-term safety and preservation. Hinging can be a tricky business, but after our workshop we’re up for the challenge!

The first Indian work on paper we successfully hinged using techniques from the workshop (2017-22-20). When executed properly, hinges can allow a work to be flipped up so the back can be viewed.

Beaded Necklaces: Restringing to Secure the Past

By Tessa Young

Who doesn’t love a beaded necklace?  They’re sold commonly today, but did you know that they were popular in the Ancient Middle East? There are a number of fabulous pieces of beaded jewelry on display in the new Middle East Galleries, and several beaded items from our collection will be featured in the Museum’s Jewelry of Ur lecture and workshop scheduled for June 14th!

https://www.futurity.org/wp/wp-content/uploads/2014/06/beads_dirt_770.jpg

Excavation of a Bronze Age necklace from a burial in the UK (Credit: Suffolk County Council Archaeological Service Contracting Team and Persimmon Homes Ltd [Anglia]) (https://www.futurity.org/shells-necklace-bronze-age-718992/)

When beaded artifacts are unearthed during excavation, typically the floss, or string, which held the beads has disintegrated in the burial environment. To ensure that the beadwork does not lose its original design, archaeologists will document their findings both photographically and through written records, and sometimes, they will string the beads onto a new piece of floss. This floss was usually good enough to get the pieces back to the museum, but it is not up to our modern conservation standards!

B15918 before treatment, with a broken strand and hasty repair tying off the ends

Here at the Penn Museum, when beadwork is destined for loans, display, or requires handling for programming, the Conservation Department wants to be sure that these objects are secure. For the upcoming Jewelry of Ur program, fellow conservation technician Alyssa Rina and I were tasked with restringing several pieces of beaded jewelry, including B15918, pictured above. The floss on this piece was previously broken and then tied off in a quick repair. The plan for this conservation treatment was to restring the beads in a loop with a more durable floss.

Depending on the piece, we restring using two different weights of braided nylon floss, which has the strength necessary to hold the beads securely while also being capable of holding knots. Monofilament (fishing line) is another popular choice, but we have found that knots can come undone rather easily with this material.

Restringing beads in a padded box using a needle in the artifact lab

Penn Museum Conservators have developed several tactics to keep the beads in place during the restringing process. First, we always keep the beads contained within a padded box, preventing the beads from rolling away and getting lost. Second, as seen in the photograph, we typically use a small clamp to secure the floss to the edge of the box. This keeps everything from shifting and rolling around. Finally, we thread the floss onto a small needle to aid in the efficiency of stringing the beads. These beads had large and regular enough holes to use a standard sewing needle, but thin, flexible beading needles are also an option.

Conservators also want to be sure that the stringing will remain in place. The first bead on the string is tied into place with two half-hitches (more-or-less a fancy double knot), and then the rest of the beads are strung into place with the help of a thin, flexible needle. If the beadwork is supposed to be a loop, at the end of the strand, the floss is threaded back through the first bead, and again tied off with two half-hitches. If the beadwork is supposed to be linear, the terminal bead is tied off with two half-hitches, making sure that the beads are tight but comfortable on the strand. Once this is done, the beads are stable enough to be handled or put on display without any fear!

B15918 after re-stringing

Conservation (training) in action

Our new curriculum intern, Marci Jefcoat Burton, was here for only couple weeks before we seemingly threw her to the wolves. That is, we asked her to work in the Artifact Lab and handle the open window sessions.

Marci describes her work to 2 visitors during an open window session

But we knew that Marci would do a stellar job working in front of the public and answering their questions. Although Marci is technically an intern, she already has extensive experience in conservation. In fact, as a curriculum intern, this is her final year of her graduate studies in conservation (she will complete her MA at the UCLA/Getty Master’s Program in the Conservation of Archaeological and Ethnographic Materials in June 2018).

One does not get to this point in their conservation training without a lot of experience working in conservation labs – to even be considered for an interview at many of the graduate programs, prospective students must have completed hundreds of hours interning with a conservator. More information about the path to becoming a conservator can be found here on the AIC website.

Marci is working on a number of projects here at the Museum, at least one of which she is basing in the Artifact Lab.

Marci working on a mosaic column drum from Al’Ubaid, Iraq (left) and examining an Islamic bowl at the microscope (right).

Stay tuned to the blog for more information about the column drum (in image above), and visit the Artifact Lab during open window hours for a chance to speak with Marci about her work!