The key reason why 3D printing was vital in the facial reconstruction process of this particular mummy, is that it allowed her face to be revealed while she remains wrapped in her sarcophagus. When a facial reconstruction is carried out without 3D printing, a skull must be moulded and cast in plaster in order to have the facial muscles built up onto the copy in wax or clay. Although the mould is taken in such a way to avoid damage to the specimen, it does put the original skull at risk, and requires specimens such as mummies to be unwrapped. Tahemaa, the mummy at the BNSS, was CT scanned in 2009 without ever having to be unwrapped, and this scan allowed me to produce a 3D print of her skull to use for facial reconstruction instead of a cast. The scan in 2009 showed more detail than a previous scan done in 1993, and revealed the mummy to have been in the age group of mid 40s - 50s, rather than in her 20s-30s, as she was previously thought to have been when her face was first reconstructed in 1996. I was able to convert the new scan files into 3D printable files and produce a replica of her skull in PLA plastic, and another in nylon.
|PLA 3D printing of the Ultimaker 2+|
|SLS nylon skull print|
I used the cheaper, PLA copy to produce a new, up-to-date reconstruction of the face of the ancient ‘Lady of the House’ at her correct age by building up facial muscles in a wax clay in the same way one would on a plaster skull, using the Manchester Method of facial reconstruction. The dearer, nylon skull was not built upon and is now on display at the museum in Bournemouth, where it is tough and durable enough to be handled by visitors - showing all the minute details visible on the scans in a relatable 3D context.
The benefit of being able to 3D print the skull at different price points with different properties is the flexibility of being able to print the same specimen in different ways for different purposes, which you wouldn’t have by just moulding and casting the original specimen in plaster. I could use an Ultimaker 2+ to save money printing the copy of the skull that would get destroyed in the moulding and casting process (which transferred the final model into the skin-like silicone), and spend more of the project budget printing the skull that would be on permanent display in the museum with an SLS 3D printer in nylon, which produced a more life-like looking object with more durable properties.
I think that using a 3D printed skull for the reconstruction process also has other advantages than solely protecting the original artefact. For one, the specimen can be reproduced countless times from a set of files that the museum has ownership and control over, which is invaluable for replacing or reproducing the museum’s interactive copy of the skull. However, I also think it can also help make it easier for the person doing the reconstruction to make the result more accurate. The process of reconstruction involves placing 32 markers on different parts of the skull to simulate the average depth of tissue at those points, which act as a guide when rebuilding the facial muscles.
|32 tissue depth pegs applied to PLA 3D print|
These depths are guided by the ethnicity, gender, age and weight of the individual in question. On a plaster cast skull, a hole is drilled at each point and a wooden peg is inserted at the right depth. Using a plastic skull, I was able to cut plastic rods to the exact right length needed and attach them with plastic glue, removing the margin for error in calculating the depth of the hole and the extra length needed on a wooden rod to fit into the hole, which is important when working to points of a millimetre.
Although it is becoming more and more common for facial reconstructions to be done digitally, 3D printing is still an invaluable resource for bringing the resulting work - or even different stages of it - into the real world. I think that this process of scanning and reproducing artefacts either as 3D digital models or 3D printed replicas is also invaluable for cataloguing and displaying all kinds of artefacts - not just skulls for facial reconstruction - in a more accessible way, and I look forward to seeing it hopefully used more and more prevalently in the museum environment.
|Reconstruction half with and half without skin layer|
|Finished facial reconstruction cast in silicone|
|Reconstruction and skull print in situ at the museum next to an old reconstruction of the mummy|
See the facial reconstruction of Tahemaa and a 3D print of her skull on permanent display at the Bournemouth Natural Science Society today.Vanessa Pearson.