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VCU Archaeology

Copycats: Casting and Molding Versus 3D Scanning and Printing

by Bernard K. Means

Last week, from March 23 to March 26, 2015, the Virtual Curation Laboratory (VCL) hosted Ray Vodden, a Research Technician at the Virginia Museum of Natural History (VMNH) in charge of their casting and molding program.  I’ve known Ray for a couple of years now, and he has always been generous with his time and knowledge when I and my students visit VMNH, including leading a recent tour (March 20, 2015) of a Virginia Commonwealth University (VCU) student-run club, the Virtual Archaeology Scanning Team (VAST). Members of VAST also examined the zooarchaeological collections maintained by Dr. Elizabeth Moore, VMNH’s Curator of Archaeology.

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During the visit, I 3D scanned some worked animal bone from a prehistoric site in Maryland and a lizard fossil that dates to the time of the dinosaurs.

Worked antler tool

Worked antler tool

 

Fossil reptile

Fossil reptile

Ray shared his expertise on casting and molding with the members of VAST, and in the past assisted now alumnus Lauren Volkers with her research examining different types of casts made from the same mold (Volkers 2014). Ray planned his recent visit to the VCL to learn the fundamentals of virtual curation, from 3D scanning of an object, through digital editing, and finally to 3D printing of the resulting digital models.

Zoe Rahsman teaches digital model editing to Ray Vodden.

Zoe Rahsman teaches digital model editing to Ray Vodden.

This visit proved of course mutually beneficial for myself and the undergraduate students working as interns in the VCL, or who are currently enrolled in my Archaeological Methods and Research Design and Visualizing and Exhibiting Anthropology courses. Ray guest lectured in both courses, and did demonstrations of making casts of a Castoroides (giant beaver) femur and humerus for the former class, as well as within the VCL itself.

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VCU student Chelsea Miller removes a cast of a giant beaver bone from a mold provided by Ray Vodden

 

Ray enlightened students about transformations in how fossilized remains are displayed in museums, from older mounts where holes were drilled directly into the fossils to display them (and irreversibly damage them) to ezpensive systems today where fossil bones are cradled within an elaborate framework that supports them without damage, and enables their removal as needed for study.

Ray Vodden illustrates mounting of fossil specimens

Ray Vodden illustrates mounting of fossil specimens

Ray’s primary role at VMNH is to cast and mold fossils, some of which are uncovered through active research by VMNH staff, and others of which are loaned to VMNH.  The casts can then be arranged into museum displays, leaving the original bones safely in storage. Multiple casts of the same bone can be made, so that a fossil can be displayed simultaneously in more than one museum, or made safely available for researchers. One of Ray’s anecdotes related to the bones associated with “Lucy,” the first member identified of Australopithecus afarensis and one that led to a major reconsideration, among other things, of the link between bipedalism and increased cranial capacity (the former preceded the latter, and not the other way around, as had once been thought). Lucy’s bones have been measured so many times that they no longer conform to their original lengths.  To avoid this issue, Ray and others strive to make very accurate casts of fossils that can be carefully measured and handled, leaving the original bones untouched.

Cast giant beaver humerus ready to be removed from its mold

Cast giant beaver humerus ready to be removed from its mold

During our discussions in my classes and as Ray learned the nuances of virtual curation in the VCL, we explored how the casting and molding process differs from 3D scanning and printing.  Typically, when Ray makes a cast, the process is somewhat laborious and time-consuming as he builds up latex half-way up a fossil (for a two-part mold) that is held in check by a clay barrier.  Once half the latex mold has hardened, he then builds up the second half of the mold on the other half of the fossil.  The latex is in direct contact with the fossil, and. rarely, this can lead to issues with the casting process, or the removal of the fossil from the latex mold.  A cast is then made, usually with a two-part resin that is mixed carefully together and poured into the mold.  Within minutes, a cast is available to be removed from the mold, waiting for the preparator to remove some excess resin as well as traces of the pour spout. The very first cast made from a mold is set aside as the most accurate copy, as the latex mold can distort over time, especially after repeated castings.  This first cast can also be used to make subsequent molds, leaving the original bone untouched from further direct and potentially damaging handling.

3D model of Miocene whale vertebra ready for printing.

3D model of Miocene whale vertebra ready for printing.

Some fossils are too delicate for the casting and molding process, which is one way that virtual curation can compliment traditional ways of replicating fossils. The VCL has so far scanned five vertebra associated with an extinct species of whale dating to the Miocene because the actual fossils are too fragile to undergo the molding and casting process.

Miocene whale atlas

Miocene whale atlas

The NextEngine Desktop 3D scanner that the VCL employs for 3D scanning uses lasers that record topological (surface) attributes of an object without making direct contact with the object–although most objects do need to be carefully placed on the scanning platform, which does involve direct contact.  Usually it takes approximately one hour to scan an artifact or fossil, and then approximately two hours to digitally edit the 3D scan to create a viable digital model.  This aspect of the process is faster than the molding process used by Ray and creates a digital model that can be virtually measured and will always produce the same 3D print if printed in the same way on the same model of printer. These digital models can be easily shared across the world, or even into space. However, the actual casting process employed by Ray is MUCH faster than 3D printing of an object, and does not have some of the issues with creating supports needed for 3D printing. The resin casts can also more closely approximate the weight of the original object.

Erica Eddins holds a freshly cast giant beaver bone.

Erica Eddins holds a freshly cast giant beaver bone.

As part of his efforts to immerse himself in virtual curation, Ray brought from VMNH a number of items for 3D scanning, editing, and printing, including a modern eastern gray squirrel (Sciurus carolinensis) to add to the VCL’s growing digital zooarchaeological collection, a fragment of a skull from a leatherback sea turtle (Dermochelys coriacea) recently donated to VMNH, a cast of a canine from a saber-toothed cat (Smilodon fatalis), and the right jugal (part of a cheek bone) from a mastodon (Mammut americanumdiscovered at the Carter bog site in Darke County, Ohio. The saber-toothed cat canine and mastodon jugal were specifically scanned to be used as part of future skeletal mounts at VMNH.  Ray needed a broken saber-toothed cat canine for a display that he is designing involving a saber-toothed cat attacking a giant beaver.

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Ray Vodden with the saber-toothed cat skeleton at VMNH

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Giant beaver skeleton

It was a simple matter to digitally break the 3D-scanned canine and print the “broken” fragment for the display–and cheaper than breaking the expensive cast.

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On a previous visit to VMNH, I 3D scanned some African lion claws that will be used in the mount of the saber-toothed cat attacking the giant beaver to add a level of drama to the recreation.  We printed copies of the lion claws for Ray during his visit.

Printed lion claws

Printed lion claws

Ray also needed a left jugal for the mastodon that he is reconstructed. Normally, Ray would sculpt the left jugal he needed by making close reference to the right jugal that he had.  This, however, would take a considerable amount of time.  In the VCL, we were able to 3D scan the right jugal and then mirror its digital model using freely available software.

Right jugal of a mastodon.

Right jugal of a mastodon.

This new left, a mirror of the right, was printed on our MakerBot Replicator the day after it was scanned and is ready to be incorporated in the mounted skeleton.

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Ray Vodden holding the right jugal up to projected image of a mastodon skull.

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Real and mirrored mastodon jugal

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Printed mirror of right mastodon jugal

One of the last items we 3D scanned that Ray brought with him was a butchered elk (Cervus canadensis) humerus, as well as painted and unpainted casts of the humerus.

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3D scanning the butchered elk humerus

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From left to right: real elk humerus, 3D print of scan, unpainted cast, and painted cast

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VCL intern Andrew Foster painting the replica of the elk humerus in reference to the actual humerus

VCL intern Andrew Foster was able to paint our 3D printed replica relative to the actual object–always an ideal situation.

Ray Vodden looks on as Natasha Cote paints a 3D printed replica

Ray Vodden looks on as Natasha Cote paints a 3D printed replica

I look forward to further conversations with Ray Vodden and the rest of the staff at VMNH as both casting and molding and 3D scanning/printing evolve in the coming years.

Ray Vodden editing a digital file.

Ray Vodden editing a digital file of a 3D scanned chimpanzee skull.

Reference cited:

Volkers, Lauren
2014    The Miss Measure of Artifacts? Examining Digital Models of Artifact Replicas to Observe Variation on Size and Form. Quarterly Bulletin of the Archeological Society of Virginia 69 (1):17-28.

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Discussion

2 thoughts on “Copycats: Casting and Molding Versus 3D Scanning and Printing

  1. I am President of the nonprofit Harris Nature Center Foundation here in Okemos, Michigan. We are creating a Michigan Fossil Dig for the community, as part of our Nature Exploration Area at the nature center, and we would love to incorporate some Fossil Giant Beaver (Castoroides) bones, along with the mastodon and mammoth ones that we have cast into cement! Is there any way we could have access to your 3-D scans of the Giant Beaver femur and humerus, so that we can print them on a 3-D printer here? I know folks share 3-D scans, but the only one I’ve come across of a Giant Beaver was a miniature version made in Denmark. Would you be willing to share yours? Please email or call me 517-648-6965. The website of our foundation is hncfoundation.org. Thank you.

    Posted by Patty Robbins | August 24, 2015, 3:45 pm

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