 Hello, I am Caroline Kuhn and I would like to first say thank you to the AIC and the tech-focused team for giving me the opportunity to take part in this conference and to talk about potential condition issues related to 3D printed materials found in our collections. My talk will mostly be based on what I have learned during my research as part of a doctoral programme with SIHA at UCL Institute for Sustainable Heritage. So as we know additive manufacturing or more commonly known as 3D printing has evolved from rapid prototyping with the invention of stereolithography in 1986 to produce prototypes not intended to last. A big hype around 3D printing occurred around 2014 as a result of the expiration of patents, opening the way for rapid developments and new materials. Indeed, since I started my research in 2013 it has been a challenge to keep up to date with developments. The range of technologies and combinations of materials are continuously increasing even today. This means that there is hardly enough time to research individual plastic formulations as we have done with more traditional plastics. With artists and designers quick to adopt and experiment with 3D printing, their presence in museums has steadily increased. Either as artworks in their own right or parts of complex composite artworks such as the zoetrope entitled Garden of Unearthly Delights by Matt Collishaw, where the main significance of the piece is perhaps less so the printed parts but rather their performance in this dynamic kinetic work. 3D printing has clearly presented museums with new challenges and opportunities, which is why we are here today. Digitally born objects due to their evolutionary intangible and ephemeral nature has meant conservation has had to evolve again. Re-evaluating and redefining traditional preservation strategies, borrowing from conservation sectors such as time based media, performance art and contemporary art conservation. As always, each work is assessed taking into consideration significance, context, artist intent, materiality and condition to delicately balance access versus preservation and resources. To do this and an understanding of the life cycle of tangible and intangible aspects of digitally born work are critical. I've heard previously of the ever expanding list of printable materials, which I can by no means cover all today. However, an awareness of current and future material design trends can help us to be proactive in preparing for their future in a museum. Due to the climate crisis, a big drive is underway for bio mimicry innovation and sustainable design for decomposition, developing water based natural biodegradable polymers, which again, due to their ephemeral nature might require a totally different approach. Here science can help inform unexpected lifespans and more sustainable display or storage options, perhaps increasing access during the objects known limited lifespan. There is also a drive for more durable materials, incorporating nanomaterials such as graphing for improved properties and smart materials designed to change because of certain external stimuli. We are collecting information upon acquisition from artists on formats, technology, significance, etc. But the information we can collect and create through material analysis can contribute to the artificial value of digital objects and virtual replicas. My talk today will however only be a brief introduction to conservation challenges related to the most common early 3D printed plastics, which is already in our collections, the originals of which we might want to keep as document of this fourth industrial revolution. We have talked a lot about replication for conservation. Replication has also allowed for exhibitions to run concurrently. But as custodians, we do need to consider sustainability in reprinting and understanding the materials, their stability and environmental impact can help us make sustainable choices. My journey of discovery into the preservation of 3D printed artwork started with an AHRC knowledge exchange program designed with heritage, a collaboration between UCL and the V&A back in 2013. I was mainly involved with the materials migration strand of the project where we set out to identify conservation issues related to 3D printed artwork. This we did through online surveys and interviews with artists and designers. The main results you see presented here. What was most alarming was that 81% of participants had noticed a physical change in their pieces in only a very brief period of time. So we ran an informal accelerated degradation study at the V&A using prints designed by the artist Tom Lomax and printed in the most common materials identified in the survey. And indeed participants observations were confirmed as can be seen in the color change seen in the sculptures on the left. What was encouraging was also that 84% of participants would like to liaise more with conservators regarding their work. It also became clear that reprinting is not an easy solution. Due to artists customizing prints post printing and other issues such as losing control over quality with resolution for example. Despite this 75% were happy to supply museums with digital poppy and 84% were happy for broken or damaged pieces to be reprinted. But despite every effort to repeat printing parameters, no two 3D prints are ever the same. The issue was investigated by Peter Walters who research color reproducibility issues related to Z Corp 3D printing. Issues related to the technological obsolescence was also picked up. The artist Jeff Mann tried himself to replicate this work. But due to technological advances was not able to as new scanners and software became smarter and automatically corrected for light reflections coming from shining objects, which is exactly the effect he was after. Another challenge with regards to reprinting is post-processing techniques as illustrated here by Sylvia Weidenbach who manually finishes her work experimenting with a range of materials and some possibly fugitive colorants. Artists also apply treatments or coatings on prints mainly to protect against UV. These are important factors to consider when deciding on cleaning techniques. Replacing them in the dishwasher like Sylvia perhaps won't be the best approach. Luckily conservation research is keeping up and new nanotechnology based materials for cleaning sensitive contemporary art substrates has been developed by the Horizon 2020 Nano restart project. Most 3D printing materials are sensitive to moisture and solvents so the hydrogels and tunable organogels could hold promise for safe and controlled cleaning. Knowing the thermal behavior of polymers and the coatings is also important when considering on storage environments such as cold storage where potential shrinkage could lead to delamination. Another interesting observation was the acceptance of color change. This is a result of a physical damage where only 34% agreed for discolored works to be reprinted and some designers factor in the tendency for the material to yellow as part of the design. Artists were asked what types of damage they have noticed in their prints. Their responses included yellowing, fading, physical damage such as breaks or distortion, dirt and in the case of metal composites, corrosion. After the design with Heritage Project, my research has focused on the light stability of 3D printed plastics. A range of studies have been done under different lighting conditions with and without UV and in different environments, increasing oxygen concentration or without oxygen, anoxia. Micro fading experiments to tell within minutes whether an artwork is light stable or not has also been conducted. Unfortunately, I do not have time to go into the results of all of this research, but I present here the results of a seven month aging experiment in daylight through glass, the plot at the top, in dark storage, one in the middle, and in dark and noxic storage at the bottom. 62 samples were printed with various 3D printed technologies and the materials were tested. Results presented here show the amount of color change which occurred after seven months. The SLA photopolymer resins which you can see in yellow were the most sensitive to light and yellowed significantly, followed by polyamide which you can see in orange. The Z-Corp 3D printed samples shown in gray showed varying degrees of color stability due to different colored inks and infiltration resins used. Polyjet photopolymers were amongst the most photostable materials tested and hardly changed color at all. ABS showed a medium sensitivity to light. An unexpected result though was that some samples changed color in dark storage, particularly polyamide, and a couple of samples also changed color in dark and noxic storage. However, overall, cutting out oxygen and light had a positive effect. There is a wealth of resources out there dealing with the with plastics conservation. This publication by Yvon Shashua gives a thorough overview of plastics and their degradation. The Pop Art Project produced an excellent publication covering condition surveys, characterization methods and conservation treatments for plastics. All these references however are geared towards traditionally manufactured plastics and although some of these plastics are used in 3D printing such as ABS and polyamide, they may behave very differently due to the manufacturing processes and changes in their formulations to aid processing. Plastics degrade due to interactions with the environment, the agents of deterioration being light, humidity, temperature, oxygen, pollutants and physical forces. Different types of degradation can occur. Physical degradation due to changes in the thermodynamic state of the plastics such as shrinking from cold storage, for example. Chemical degradation due to reactions with light called phatolosis, which can break bonds and form highly reactive free radicals. Chemical reactions involving light and oxygen, photo oxidation, as well as thermal oxidation, which is without light, and hydrolysis can occur, which is reactions with water or moisture. Physicochemical reactions include the absorption of moisture into the polymer or the diffusion of plasticisers out of the polymer, which not only cause the shrinkage and embrittlement but can pose a hazard to surrounding objects as could releasing volatile organic compounds. More research is needed to establish which 3D printing plastics might be hazardous and need to be stored separate from other objects. Also to define storage conditions, such as open or closed storage due to potential acidic vapors or plasticisers loss. Cold storage is often suggested for plastics due to reducing reaction rates significantly. However, we need to consider whether this is a safe option for 3D printed plastics due to their anisotropy and the potential stress they might be under in cold conditions and this could lead to distortion. Plastic shrink when cooled and although this is reversible, this could cause delamination of coatings or introduce internal stresses with composite objects. Cooling can also pose a risk due to condensation, particularly for highly hygroscopic plastics such as polyamide 12 used in SLAs. So let us look in more detail at the individual polymers starting with polyamide also known as nylon. The number suffixes refer to the amount of carbon atoms present. Polyamide 6 filaments is used in fused deposition modelling and polyamide 12 powders for selective laser sintering. Popular due to its relatively robust mechanical properties and good chemical resistance to a variety of common solvents. Laser-sinted polyamide is advertised as having mechanical properties matching that of its injected moulded counterparts. However, the mechanical stability is greatly impacted by building parameters such as laser wavelength, energy and temperature distribution within the build chamber. The density and porosity of the sintered parts depend on particle size and how densely these are packed in the build chamber. Increased porosity could impact stability by increasing access to atmospheric oxygen. Using recycled powders can also affect print quality. Chemical degradation studies into polyamide has mainly been for nylon in the textile industry. Polyamides are known to undergo photo oxidative degradation becoming yellow and more brittle. Yellowing in dark storage also occur known as post irradiation or secondary yellowing. Due to thermal oxidation reactions continuing on products formed during photo degradation, particularly in the presence of atmospheric moisture. Polyamide is one of the most hygroscopic plastics and filaments and SLS-powdered polyamide can absorb up to 10% of its weight in moisture. Prints will react dimensionally to moisture absorption, so extreme fluctuations in relative humidity can lead to cracks. High relative humidity can also promote hydrolysis, a reaction by which ester bonds break to produce acids and other products. The most common polymers used in fused deposition modelling are that of acrylonitrile butadiene styrene, ABS and polylactic acid. ABS's mechanical properties can be fine-tuned by varying the proportions of the different components and combining with other materials such as polycarbonate. Injection moulded ABS has high impact resistance, but again printing parameters can impact tensile strength and increase amusotropy. The primary degradation mechanism of ABS is that of photo oxidation and ABS is also highly hygroscopic with ABS filaments if not stored correctly can absorb moisture leading to poor quality prints. ABS is sensitive to some solvents and soluble in esters and ketones with acetone primarily being used for post processing smoothing. Extensive studies has been done for health reasons into VOCs emitted from FDM during printing. However, a study into VOC emissions at room temperature from FDM polymers to assess this to suitability as a conservation material found that ABS emitted significant amounts of styrene, which could pose a danger due to potential solvent action on artist materials. PLA is a biodegradable copolymer consisting of lactic acid and glycolic acids. It is only biodegradable when composted at temperatures above its glass transition temperature. PLA degrades via both photo oxidative and hydrolytic mechanisms and PLA is more hygroscopic than ABS and is soluble in a range of solvents with ethyl acetate vapour used for surface smoothing. Due to the colour possibilities afforded by Z-Corp 3D printing, it has been popular amongst artists. The exact compositions are trade secrets but safety data sheets can provide some information. Cyanolacrylate is often used for infiltration due to its rapid curing initiated by the presence of the hydroxyl anion in water, which is why superglue always prefers your fingers to the object. If parts are not fully dried, cyanolacrylate will react at the surface, blocking pure pores and thereby limiting the depth of infiltration. An accelerated photodegradation study by Maya Stanek found that in the case of Z-Corp printing inks, magenta was the most fugitive, followed by cyan and then yellow. Uncoloured samples infiltrated with cyanolacrylate and epoxy was also tested, with epoxy infiltration leading to increased yellowing. A study into the suitability of cyanolacrylate as an adhesive for fossils found that cyanolacrylate tends to degrade under UV light in alkaline and moist conditions, hydrolysis leading to the formation of formaldehyde and cyanolacetate. As museums cut out UV and carefully control their humidity, there should not be an issue. Stereolithography, being the most important and established 3D printing technology, has inspired others' SLA technologies, including DLP, LCD and CLIP. They all employ photopolymers, the simplest definition of which is a polymer formed via a polymerization process brought upon by direct or indirect interaction with light. They are very complex hybrid polymers, generally consisting of four basic components, monomers, oligomers and photoinitiators, and other additives such as photostabilizers are also added. Typically, acrylate or methacrylate monomers are used as they are very reactive and readily formed bonds with other polymers such as epoxy, polyurethane, polyester and polyether to impart desired properties. For example, acrylates are prone to shrinking and are hard rigid plastics, so they are copolymerized with epoxy to increase dimensional stability and polyurethane for flexibility. However, the polymerization reaction needs to be initiated, so photoinitiators are added, which upon exposure to light, break down forming highly reactive free radicals. Photoinitiators absorb at specific wavelengths, so to broaden their spectral range, photosensitizers are added. There are different photoinitiating systems and more than one type of photoinitiator can be added to hybrid systems. Some photoinitiators have been found to contribute to the yellowing of resins, in particular tri-sulfonium salts used to polymerize epoxies. With Norrish type 2 photoinitiators used in acrylate systems, curing is inhibited by oxygen, a property which Clip Technology uses to its advantage. SLA resins are highly photosensitive due to both photoinitiators used and the higher ratio of epoxy to acrylate in the base polymers. FTIR analysis during experiments at UCL indicated that despite post curing being conducted after printing, some SLA resins were not yet fully cured. The concern as residual photoinitiators are known to lead to increased yellowing. High-performance liquid chromatography identified the presence of both tri-sulfonium salts and Igroquia-184, a type 1 photoinitiator which has been found to not significantly contribute to yellowing. Further additives are also added to SLA resins such as photo-stabilizers, flame retarders, dyes and pigments. SLA resins should be considered as dynamic with competing reactions going on between photosensitizers and photo-stabilizers during its lifetime. And once these photo-stabilizers have been depleted, the rate of yellowing can increase. SLA resins polymerized by both free radical and cationic mechanisms, a characteristic of the latter being that of dark curing, where light is only needed to initiate the reaction after which curing can proceed without it. A problem with predicting the photo response of SLA resins is that the point where curing stops and photo oxidation begins is blurred. Multi-jet printing with Polyjet is favored due to its high precision, fine detail and ability to print smooth surfaces. What also sets it apart from other 3D printing technologies is Polyjet's digital materials, which through the blending of 29 base resins during printing, allows for thousands of digital material options to be combined within a single print, ranging from rigid to flexible, for example. Post cure is not typically needed for Polyjet projects, but a support structure consisting of a combination of propylene, acrylic monomers, polyethylene and glycerin needs to be thoroughly cleaned off. The digital materials are predominantly acrylate and methacrylate based. These are reasons of choice and conservation due to their good photo stability. For initiating Polyjet resins, use type 1 photo initiators, including IgroCure 184, an important commercial non-yellowing photo initiator, due to the absence of aromatic components which prevents the formation of chromophores which lead to yellowing. However, photo bleaching does occur and strategists for their vero-clear resin recommends post cure photo bleaching to improve color and translucency. Little is known about added additives or platicizers in these materials. In order to care for our 3D printed collections, it is crucial that we know what they are composed of. Names can be confusing. For example, the digital material ABS-like, which is not an ABS at all, but a photopolymer. Again, the Pop Art project provides useful information on methods of analysis. Of course, non-invasive techniques are preferable and here spectroscopic analysis holds the key. FTIR is an established method for polymer identification and in my studies I used ATR, FTIR and principal component analysis. And this was very useful in grouping different types of photopolymer resins, monitoring their oxidation and to identify not fully cured resins. FTIR is increasingly found in conservation labs and studios. And there are studies underway by Dr. Julian Bell and Petronella Nell from Australia to optimize the application of these techniques on three-dimensional plastic objects in museums. They have produced a flowchart of best practice for FTIR. This offers huge potential for institutions to collect, develop and share spectral databases specifically for 3D printed materials. XRF analysis can be used for identifying fillers or metal components in 3D printed composites. In the case of photopolymers, UV-Vis analysis can be very informative in identifying the presence of photo initiators and the state of cure of objects. However, perhaps we need to proceed with caution. The two images on the bottom left show me taking UV-Vis spectra of a sculpture before subjecting it to accelerated LED aging. The image at the bottom is of the sculpture after aging. A dark discoloration appeared at the exact spot where I collected spectra from, which was a dense part of the resin, possibly containing residual photo initiators. A concerning find and worth further investigating to see if spectral analytical techniques has potential for damage. There are no studies involving analysis of VOC emissions from photopolymers. Solid phase micro-extraction, SPMI GCMS has been used for VOC analysis of heritage objects and can provide valuable information regarding degradation processes. Currently, there is also valuable research conducted at UCL Institute for Sustainable Heritage with the complex project led by Dr. Catherine Curran. Using a systems dynamic approach to model and interpret interconnected physical and chemical interactions taking place in historic plastics over time. This approach could hold potential to untangle the complexities of 3D printed plastics. There is so much we do not know about these novel new materials and the only way to be proactive in overcoming future conservation challenges is through collaboration, not just with other institutions and artists but also industry. There is a need for further research and through conferences like this, perhaps an opportunity to develop further international research projects. Thank you so much for listening to me. I look forward to your questions and please do get in touch for any collaborations. Thank you.