LABELS FOR ETERNITY: TESTING PRINTED LABELS FOR USE IN WET COLLECTIONS

LABELS FOR ETERNITY: TESTING PRINTED LABELS FOR USE IN WET COLLECTIONS G.G. BEINER National Natural History Collections at the Hebrew University of Jerusalem, Berman Building, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel gali.beiner@mail.huji.ac.il Key words.—collection, fluid-preserved, immersion, label, Oddy test, printer, solution. INTRODUCTION While handwritten labels with India ink are often time proven (Carter 1998, Jackson 2013), the life span of modern printed labels is difficult to predict. The introduction of electronic database systems made computer-generated, printed labels the method of choice. Up to now, there were no common standards for such labels, and printer technologies have been constantly changing. The conservation and preparation community has yet to agree on a set of standards for printed labels for use both in fluid-preserved and in dry collections. Surveys on the use of printed labels in fluid-based collections indicate that the range of printers, inks, and printing substrates is considerable (Beccaloni 2016). Fast technological turnover and the often-limited life span of printers further complicate the situation. For example, users of some black-and-white inkjet printers received good experience using high resolution (1,200 dpi) black-and-white printing, but the models of monochrome printers recommended for collections are being discontinued, and the performance of color printers has yet to be tested for stability (J.M. Gagnon, Canadian Museum of Nature, pers. comm.). An excellent starting point to explore the diversity of printers is the Society for the Preservation of Natural History Collections (SPNHC) Wiki information page, which summarizes key data on different types of printers currently in use (SPNHC 2020). Three main types can be distinguished: thermal transfer, inkjet, and laser printers. Laser printers use a toner, which is a powdered carbon-based ink. While Zala et al. (2005) found that laser-printed labels produced by an Apple LaserWriter Plus printer are durable in 70% ethanol in distilled water or in 10% unbuffered formalin, they were concerned about the longevity of the toner-paper bonding. As detailed in Zala et al. (2005) and the SPNHC Wiki page— and confirmed by personal observations in the National Natural History Collections at the Hebrew University of Jerusalem (NNHC-HUJ)—the letters present on laser-printed labels often delaminate from the printing substrate over time. Consequently, laser printers are not recommended for use in fluid-based collections. Therefore, our study compares only inkjet Collection Forum 2020; 34(1):101–113 © 2020 Society for the Preservation of Natural History Collections Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Abstract.—Will printed labels survive prolonged immersion in collection fluids, and, if so, which printing system is preferable: inkjet, laser, or thermal transfer printing? In a world with a wide variety of printers, printing substrates, and printer technologies, the interactions between them very likely affect long-term label preservation in the chemical environment of the preservation fluid. In fluid-preserved collections, the main issues frequently encountered with labels include delamination, abrasion, fading, and disintegration during immersion in solutions such as ethanol and formaldehyde aqueous solution (widely known under the commercial name formalin). Very few publications have presented testing procedures assessing the behavior and stability of printed matter immersed in the types of solvents used in fluid-based collections. This article presents a series of experiments set up at the National Natural History Collections at the Hebrew University of Jerusalem to test a variety of museum labels. The tests compared labels actually used in different natural history collections and included labels from both thermal transfer and inkjet printers. All were subjected to accelerated aging and mechanical abrasion. In our series of tests, inkjet labels gave the best performance. 102 COLLECTION FORUM Vol. 34(1) Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 to thermal transfer printers. These methods differ fundamentally. Thermal transfer printing involves coating on a plastic surface, while inkjet printing is injected into the paper and is soaked by it. The key question that collection professionals still face is the question of label and ink permanence when the labels are placed inside the sort of fluids prevalent in fluid-based collections. Inkjet printers use either toners or liquid inks, which may be pigment based or dye based. Carbon pigment-based inks should be preferred, as they have better permanence qualities compared to dye-based inks, as demonstrated by experimentation (Jackson 2013). However, pigments form only one ingredient in the list making up the ink. Inkjet inks are required to be liquid when they are jetted from the ink head. They are usually composed of a functional molecule (e.g., a colorant, which may be a pigment), a liquid vehicle (water, organic solvents, or cross-linkable monomers), and additives with specific functions (surfactant, preservative, or photoinitiator) and often also include a binder—a polymer for binding the functional molecules to the substrate after printing (Magdassi 2010). Additives such as anionic surfactants or polymers with hydrophobic groups may be added by the manufacturer to prevent agglomeration of insoluble particles of pigments (such as carbon black) in the ink cartridges after production and filling, which may block print nozzles (Magdassi 2010). Consequently, conventional inks usually contain pigment at concentrations below 10% w/w in order to achieve the necessary optical density (Magdassi 2010). In summary, inks of commonly used inkjet printers are not standardized and are highly variable in their composition. The quality and durability of the printing may vary, depending on the manufacture of the ink. Moreover, inkjet printers are often designed to be used with specific paper to optimize the performance of the ink and the printing quality. This is done with different coatings on the surface and bottom layer of the paper. Inkjet printers employ different paper qualities and standards, both coated, such as with kaolin (Bundy and Ishley 1991), and uncoated (e.g., chemically inactivated tracing paper). Various websites offer information on a variety of paper finishings (e.g., WebFX 2013, Printivity Insights 2019). The information on the chemical processes involved in achieving these finishings is scarce, and the term “archival” does not have a standardized meaning. Thermal transfer printers employ a toner ribbon, which melts wax or resin-based ink into the printing substrate. The ribbon serves as solid-state ink, applied as a very thin coating onto polyester film, which serves as the printing medium. This ribbon is drawn between the medium and the inkhead, where tiny pins, each representing a pixel, rapidly heat and cool to melt and transfer the ink ribbon onto the blank substrate (CableOrganizer 2021). Thermal printers vary in pixel size and density. The three main types of thermal transfer inks include wax, wax–resin, or pure resin ribbons (CableOrganizer 2021). Pure resin ribbon inks are considered the most durable but are designed for use on vinyl, polyester, and polypropylene printing media and thus are unsuited for use on paper (CableOrganizer 2021). Thermal transfer printers should not be confused with direct thermal printers. Thermal transfer printing involves the use of a printing ribbon, while direct thermal printing excludes the use of ribbons. The ribbon acts as a buffer between the print substrate and the print head, helping to protect the latter from dust and debris, which could burn into it and reduce the quality of the print. Thermal transfer printers are cheaper and may lack the necessary hardware for controlling and driving a ribbon. Thus, they produce less durable prints. Conversely, direct thermal printing substrates of high quality are more costly than thermal transfer printer substrates because plainer, more abrasive printing substrates damage the printer head in direct thermal printers (SATO America 2015). Alpha Systems Inc. (Elkhart, IN) offers a BEINER—LABELS FOR ETERNITY 2020 103 Table 1. Specifications of tested museum labels. Type Thermal transfer Inkjet China ink (Pelikan) 2HB pencil Datamax i-Class Mark II+ pure resin ink ribbon (300 dpi) Epson WF-3010 + Epson DURABrite ink cartridges Lexmark MS310dn + 501H high-yield return program toner cartridge n/a: ink applied with a pen nib n/a: pencil applied manually Substrate Preservation Tag spun-bond polyester media Resistall 100% cotton fiber paper FLEXDura HE permafiber wet strength 6-point paper Rite in the Rain all-weather printing paper, 75 g/m2 , USA Rite Green Rite in the Rain all-weather printing paper, 75 g/m2 , USA Rite Green ID Code KU BMNH RBCM RR + China ink RR + 2HB pencil KU = University of Kansas Natural History Museum. BMNH = Natural History Museum London. RBCM = Royal British Columbia Museum. RR = Rite in the Rain all-weather printing paper. combination of pure resin-based ink from a Datamax thermal transfer printer and a label substrate made of spun-bound polyester for use in fluid-based collections (Bentley 2004). Fluid-preserved collections historically include an interesting range of fluids, but ethanol and denatured alcohol appear to be the most prevalent in current use (Beccaloni 2016). Another still often encountered preservation fluid in collections is formalin. In order to test the permanence of printed labels immersed in fluids, we conducted a series of accelerated aging experiments comparing different types of printed museum labels before and after immersion in commonly used solutions, such as ethanol and formalin. EXPERIMENTAL SETUP Different labels actually used in museum collections were used for this study (Table 1). Tested labels include prints from two inkjet printers and one thermal transfer printer, the specifications of which are given in Table 1. The label types in terms of material are identified in the table and the following discussion by their respective museum acronyms— BMNH (Natural History Museum London), RBCM (Royal British Columbia Museum), KU (University of Kansas Natural History Museum)—or the name of the company that produced the label material (RR, for Rite in the Rain all-weather printing paper). Two handwritten labels, one with China ink on RR paper and the other with 2HB pencil on RR paper, were used in the first experiment for comparison. For each of the experimental settings, identical letters from identical locations and identical size were extracted from the labels, using scissors previously cleaned with 99.5% acetone (AR) and then with 99.9% absolute ethanol (Baker Analyzed line of products produced by the J.T. Baker Chemical Co., Radnor, PA) prior to each removal. The condition of each sample was documented before and after treatment (see details under “Analytical Methods”). All aqueous solutions of formaldehyde used in the tests were prepared from a supplier stock solution of 38% (w/w) Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Inkjet Printer 104 COLLECTION FORUM Vol. 34(1) Experiment 1 In this group, we compared samples including label substrate plus print with samples including plain label substrates only (see Table 2 for details). Each sample was placed together with a magnetic stirrer in 3.50 ml of the test solution in a completely new glass scintillation vial (20 ml, screw-cap tube). Both tubes and stirrers were cleaned with 95% ethanol and air-dried before the test. The glass vials were placed for 24 hours on a Variomag® poly 15 magnetic stirrer shaker plate, the temperature set to 80°C. Experiment 2 Each sample was placed in 5 ml of the test solution (Table 2) within glass vials (CAP1000191PK-72 US-manufactured screw-on-cap vials) exposed to UV irradiation in a crosslinker with 8 UV lamps for 30 minutes to eliminate biological contamination. Afterward, vials were rinsed in 99.5% cetone (AR), finally cleaned with 99.9% absolute ethanol (Baker Analyzed), and air-dried. The glass vials were placed in a shaking water bath (Tuttnauer Co., Jerusalem, Israel) with 15 shakes per minute at 80°C for 72 hours. Experiment 3 The setup for Experiment 3 was identical to the setup for Experiment 2 except for the addition of half a teaspoon of glass spheres (Tambour Fantasy ball glass 795-50X) to each vial to test the stability of the labels and their printing against abrasion and wearing. Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 of formaldehyde (Bio-Lab Ltd, Jerusalem, Israel) and diluted to 4% using distilled water from a Treion TSDI column (Treitel Chemical Engineering Ltd, Tel Aviv, Israel). The first experiment (Table 2) served as an initial evaluation to gain insight into the effects of different solutions (i.e., ethanol, formalin, ethyl methyl ketone, and methyl sulfoxide) at specific concentrations on printed thermal transfer and inkjet labels and to determine whether these labels were more or less durable compared to handwritten labels. The next two experiments focused more specifically on the types of labels that had shown deterioration in the first experiment, including an additional type of inkjet label (Table 2). These labels were tested in 4% formalin and 95% ethanol, with distilled water for comparison. Ethanol and formalin were also selected because they are the most commonly used solutions in fluid-preserved collections. The third experiment added one new factor: a test for abrasion and wearing effects using glass spheres under accelerated aging conditions designed according to Oddy test protocols (reasoning, origins, and variations on the original procedure have been described in a number of publications, e.g., Oddy 1973, Green and Thickett 1995, Robinet and Thickett 2003, Thickett and Lee 2004, Beiner et al. 2015). In the field of conservation, the so-called Oddy test for museum materials aims at creating conditions extreme enough to trigger fast change, based on the idea that slow change achieved over long periods of time would result in the same set of changes. For the experimental setting, it is assumed that elevated temperatures accelerate chemical reactions, which usually occur slowly over time, and damages thus occur faster and are more easily observable, that is, within the (relatively short) time span of the Oddy test. Therefore, our three experiments were conducted at 80°C. The initial Experiment 1 was set to a shorter time span (24 hours) because we wished to test our assumption that chemical change likely takes place very quickly at increased temperatures of 80°C and would be traceable in our chemical analyses. The next two experiments were conducted over a longer time span (72 hours) because we wanted to test the integrity of the printing and/or the substrate against wearing and abrasion. The test conditions for all three experimental setups are summarized in Table 2. BEINER—LABELS FOR ETERNITY 2020 105 Table 2. Details of the experimental setups for thermal transfer, inkjet, China ink, and pencil labels tested for this study. Institutional abbreviations as in Table 1. Experiment 1 shows the results of label types from Table 1 tested in different solutions and concentrations, with a magnetic stirring rod for agitation. Experiment 2 shows the results of testing labels exhibiting deterioration in Experiment 1 in solutions of 4% formalin and 95% ethanol compared with distilled water with agitation in a shaker bath. Experiment 3 shows the results of the same experimental protocol as Experiment 2 but with further agitation provided by glass spheres. All three experiments were conducted under accelerated aging conditions of elevated temperature (80°C) designed according to Oddy test protocols. Experiment 1 I II III IV V VI VII VIII IX X X XI XII XIII XIV XV XVI XVII XVIII Experiment 2 I II III IV V ID or Source Solution Volume Temperature (ml) (°C) Abrasion Time (hr) Change BMNH BMNH BMNH BMNH BMNH unprinted BMNH unprinted BMNH unprinted KU KU KU KU unprinted KU unprinted KU unprinted China ink + RR China ink + RR 2HB + RR 2HB + RR RR only RR only MEK Ethanol 95% Formalin 4% DMSO Ethanol 75% 3.50 3.50 3.50 3.50 3.50 80 80 80 80 80 Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer 24 24 24 24 24 No No Fixation? No No Ethanol 95% 3.50 80 Magnetic stirrer 24 No Formalin 4% 3.50 80 Magnetic stirrer 24 No Ethanol 75% Ethanol 95% Formalin 4% Ethanol 75% Ethanol 95% Formalin 4% Ethanol 95% Formalin 4% Ethanol 95% Formalin 4% Ethanol 95% Formalin 4% 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 80 80 80 80 80 80 80 80 80 80 80 80 Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer Magnetic stirrer 24 24 24 24 24 24 24 24 24 24 24 24 Abrasion loss Abrasion Loss No No No No Fixation? No Fixation? No No KU-7 KU-8 KU-9 KU-10 KU-11 Ethanol 99.9% Ethanol 99.9% Formalin 4% Formalin 4% Doubledistilled water Ethanol 99.9% Ethanol 99.9% Formalin 4% Formalin 4% Doubledistilled water Ethanol 99.9% Ethanol 99.9% Formalin 4% Formalin 4% Doubledistilled water 5 5 5 5 5 80 80 80 80 80 None None None None None 72 72 72 72 72 Craquelure Craquelure No No No 5 5 5 5 5 80 80 80 80 80 None None None None None 72 72 72 72 72 No No No No No 5 5 5 5 5 80 80 80 80 80 None None None None None 72 72 72 72 72 No No Fixation? Fixation? No VI VII VIII IX X RBCM-1 RBCM-2 RBCM-3 RBCM-4 RBCM-5 XI XII XIII XIV XV BMNH-8 BMNH-9 BMNH-5 BMNH-6 BMNH-7 Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 No. 106 COLLECTION FORUM Vol. 34(1) Table 2. Continued No. KU-13 KU-14 KU-12 KU-15 KU-16 VI VII VIII IX X RBCM-6 RBCM-7 RBCM-8 RBCM-9 RBCM-10 XI XII XIII XIV XV BMNH-10 BMNH-11 BMNH-12 BMNH-13 BMNH-14 Volume Temperature (ml) (°C) Solution Ethanol 99.9% Ethanol 99.9% Formalin 4% Formalin 4% Doubledistilled water Ethanol 99.9% Ethanol 99.9% Formalin 4% Formalin 4% Doubledistilled water Ethanol 99.9% Ethanol 99.9% Formalin 4% Formalin 4% Doubledistilled water Abrasion Time (hr) Change 5 5 5 5 5 80 80 80 80 80 Glass spheres Glass spheres Glass spheres Glass spheres Glass spheres 72 72 72 72 72 Craquelure Craquelure No No No 5 5 5 5 5 80 80 80 80 80 Glass spheres Glass spheres Glass spheres Glass spheres Glass spheres 72 72 72 72 72 No No No No No 5 5 5 5 5 80 80 80 80 80 Glass spheres Glass spheres Glass spheres Glass spheres Glass spheres 72 72 72 72 72 No No Fixation? Fixation? No MEK = 99.5% ethyl methyl ketone (C4H8O). DMSO = 99.9% methyl sulfoxide (C2H6OS). ANALYTICAL METHODS All tested labels in all three parallel experimental groups were subjected to visual examination and image capture before and after testing with a Stereo Discovery V8 Zeiss microscope at three different magnifications (×1, ×2.5 or ×3, ×8). In Experiment 1, solvents in selected test containers were analyzed using ultraviolet-visible spectroscopy (UV/Vis) using a HP 8453 diode array spectrophotometer aimed at detecting potential “leaks” due to migration of chemical components from the ink on the labels into the solvent (Figs. 1, 2). Liquids from the same select test containers were also analyzed using tandem mass spectrometry (MS/MS) in an Agilent 6520 QTOF analyzer (Fig. 3). This type of analysis is used to separate and detect ions in organic substances, mainly carbon, hydrogen, nitrogen, and oxygen, and is sensitive to smaller quantities than UV/Vis analysis. For both analyses, the tested liquids were taken directly from the test containers after the experiment. The results from each type of analysis were compared to results from blanks, that is, liquids from the same stock solutions taken from test containers with and without labels in them. RESULTS Experiment 1 The BMNH inkjet labels exhibited no visual change (Fig. 4) other than the fact that paper fibers recovered from accelerated aging in 4% formaldehyde showed slight swelling (noted in Table 2 as a “fixation” effect). This may be caused by the formaldehyde, which can induce swelling of the cell wall in some pulp fibers and binding of water molecules to the Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Experiment 3 I II III IV V ID or Source 2020 BEINER—LABELS FOR ETERNITY 107 fiber surface (Maloney and Paulapuro 1998) or can cause disruption of interfiber bonds to alter the original properties of the dry paper (Vitale 1993). Paper labels with China ink and labels with 2HB pencil markings likewise displayed some “fixation” effects in formalin but otherwise displayed no visual change. KU thermal transfer labels all exhibited marked visual damage after accelerated aging in 75% ethanol, 95% ethanol, and 4% formaldehyde in the form of fine abrasion lines and actual loss of imprint (Fig. 5). In addition to visual examination of the labels, solvents from selected test containers subjected to UV/Vis analysis yielded the results presented in Figure 1. The analysis compared results from solutions that had contained label substrate only with results obtained from solutions with imprinted labels. Interestingly, this type of analysis detected little or no components from machinegenerated print that leached from the KU thermal transfer labels in 75% ethanol (Fig. 1A) with nearly identical graph lines for liquids from containers with substrate plus ink versus substrate only. Some change in the liquid was detected for KU thermal transfer labels in 95% ethanol (Fig. 1B) and in 4% formaldehyde (Fig. 1C), while samples with BMNH inkjet labels exhibited considerably greater change (Fig. 1A–C) despite their exhibiting no visual ink loss. In an effort to confirm or refute these results, the liquids were also analyzed using MS/MS. Containers with 95% ethanol and 4% formaldehyde were subjected to MS/MS analysis (Fig. 3A, B). The greater number of “new” peaks in the results of the MS/MS Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Figure 1. (A) Experiment 1 results comparing UV/Vis analysis for 75% ethanol containing label substrate with and without print. (B) Experiment 1 results comparing UV/Vis analysis for 95% ethanol containing label substrate with and without print. (C) Experiment 1 results comparing UV/Vis analysis for 4% formalin containing label substrate with and without print (all images © NNHC-HUJ, G.G. Beiner). 108 COLLECTION FORUM Vol. 34(1) analysis in ink-plus-label-substrate samples compared to label-substrate-only samples confirm that the BMNH inkjet labels may have leached considerably more printing components into the surrounding environment when immersed in 95% ethanol compared to immersion in 4% formaldehyde under accelerated aging conditions. As a final note to these results, it should be stated that results from UV/Vis analyses on liquids from containers with RR paper substrate with and without China ink or 2HB pencil markings in 95% ethanol and in 4% formaldehyde (Fig. 2A, B) indicate a very high likelihood of “leaching” of ink or pencil components into the solvent environment from these handwritten labels. Experiments 2 and 3 In light of the results obtained from Experiment 1, it was postulated that possible reasons for the visible damage to some labels could be insufficient cleaning of the test containers, chemical contamination of the water used to prepare the formaldehyde solution, Figure 3. (A) Experiment 1 results comparing MS/MS analysis for 95% ethanol containing label substrate with and without print. (B) Experiment 1 results comparing MS/MS analysis for 4% formalin containing label substrate with and without print (all images © NNHC-HUJ, G.G. Beiner). Arrows in (A) and (B) indicate substance present due to possible leaching of ink. Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Figure 2. (A) Experiment 1 results comparing UV/Vis analysis for 95% ethanol containing RR label substrate with and without China ink or 2HB pencil. (B) Experiment 1 results comparing UV/Vis analysis for 4% formalin containing RR label substrate with and without China ink or 2HB pencil (all images © NNHC-HUJ, G.G. Beiner). 2020 BEINER—LABELS FOR ETERNITY 109 or contamination of the ethanol stock solution obtained from suppliers. Therefore, the experimental settings for parallels 2 and 3 were adjusted to use higher purity levels of solvents and decontamination (see experimental settings). However, both groups showed similar results (Figs. 6, 7) again. A possible explanation why the printed surfaces in Experiment 3 showed few abrasion effects is that the horizontal shaking of upright standing containers with glass spheres led to stirring rather than to shaking and thus to less abrasion. In the groups from both experiments, the printing on BMNH and RBCM inkjet labels was not visibly damaged by accelerated aging either in 99.9% ethanol or in 4% formaldehyde, while the KU thermal transfer labels exhibited visible cracking (“craquelure”) of the imprint in 99.9% ethanol. Otherwise, the only effect on the visual integrity of the label substrates remained the swelling of paper fibers in BMNH labels immersed in formalin. It should be noted that this “fixation” effect was visible only in printed areas, possibly because the print made it easier to notice. This effect was not detected in samples immersed in distilled water or in RBCM labels, implying, first, that the “fixation” effect may be connected to the presence of formaldehyde and, second, that one factor involved in its visibly detectable appearance may be the type of paper. The potential cause of the observed damage to the imprint in the KU thermal transfer labels, that is, the cracks in the toner-ribbon layer in Experiments 2 and 3 compared to the fine abrasion lines and ink loss in Experiment 1, may be because of the different mode of abrasive action caused by glass spheres (used in Experiments 2 and 3) as opposed to magnetic stirrers (Experiment 1). The mode of abrasion might not have been the only cause. The observed differences may also correlate with slightly larger glass containers and thus larger space inside the test containers and the prolonged exposure of 48 hours under these settings that caused more damage to printed surfaces. Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Figure 4. Experiment 1 results showing BMNH inkjet and thermal transfer labels, ×3 and ×8 magnification; images obtained from a Stereo Discovery V8 Zeiss microscope (© NNHC-HUJ, G.G. Beiner). 110 COLLECTION FORUM Vol. 34(1) Figure 6. Experiment 2 results comparing inkjet and thermal transfer labels, ×2.5 magnification, under a Stereo Discovery V8 Zeiss microscope (© NNHC-HUJ, G.G. Beiner). Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Figure 5. Experiment 1 results showing KU thermal transfer labels, ×3 and ×8 magnification; images obtained from a Stereo Discovery V8 Zeiss microscope (© NNHC-HUJ, G.G. Beiner). 2020 BEINER—LABELS FOR ETERNITY 111 CONCLUSIONS Three sets of different experimental settings exposed a variety of labels to accelerated aging experiments in preservation fluids typically found in fluid-preserved collections. In all three groups, inkjet labels remained remarkably stable compared to thermal transfer labels, although it seems that the paper as a printing medium may leach more ink components into the immersion environment. Although only long-term observations under real-life conditions in collections are suited to evaluate the durability of labels in such diverse and physically and chemically complex environments such as fluid-based collections, experimental testing in typical storage fluids under accelerated aging conditions allows insights to be drawn from the performance of these labels. In conservation, artificial testing by submitting objects or substances to extreme conditions to trigger fast changes or reactions as in the Oddy test rests on the idea that slow changes observed over long time periods are caused by the same or similar physical parameters. By “accelerating” these processes, such as through accelerated aging experiments, the observation span until effects become visible could be reduced. The three experiments presented here are based on this premise and differ from “normal” collection storage conditions in two main factors: the temperature regime and potential abrasion. The test temperature was raised to 80°C with the specific aim of accelerating chemical processes, in accordance with prevailing Oddy test protocols, and thus markedly differs from common temperature settings in storage spaces dedicated to fluid-based collections. The rounded magnetic stirrers used in Experiment 1 and the rounded glass beads used in Experiment 3 were added in effort to simulate many years of object movement against labels within a Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Figure 7. Experiment 3 results comparing inkjet and thermal transfer labels, ×2.5 magnification, under a Stereo Discovery V8 Zeiss microscope (© NNHC-HUJ, G.G. Beiner). 112 COLLECTION FORUM Vol. 34(1) ACKNOWLEDGMENTS I would like to thank the following people for their contribution of museum labels for testing: Andy Bentley (ichthyology collection manager, University of Kansas Biodiversity Institute, USA); Heidi Gartner (collection manager and researcher, Invertebrates, Royal BC Museum, Canada); James Maclaine (senior curator, Fish Section, The Natural History Museum, London, UK); and Joe Panella (Alpha Systems, Inc., USA). Thanks to Racheli BenKnaz Wakshlak from Prof. D. Avnir’s lab at the Institute for Chemistry at the Hebrew University for performing the UV/Vis analysis; to Prof. Carina Hazan from the Microanalysis Lab at the Institute of Chemistry, the Hebrew University, for performing the MS/MS analysis; and to Prof. Simon Emmanuel and Yoni Israeli from the Institute of Earth Sciences at the Hebrew University for facilitating use of the Zeiss microscope. Thanks also to Jean-Marc Gagnon (curator, Invertebrate Collections, Canadian Museum of Nature) and to Dirk Neumann (Ichthyology Section, Zoologische Staatssammlung München, Germany) for their information and advice on printers and labels. Special thanks to Prof. Gila Kahila Bar-Gal, head of the NNHC-HUJ, and to Prof. Rivka Rabinovich, head of the Palaeontology Lab, at the Hebrew University for their support that enabled and facilitated these experiments and for the funding the chemical analyses. Thanks also to the reviewers of the manuscript, Dirk Neumann and Julian Carter (Natural Sciences, National Museum Wales, UK). Résumé.—Les étiquettes imprimées survivront-elles à une immersion prolongée dans les liquides de conservation et, si oui, quel système d’impression est préférable? L’impression par jet d’encre, laser ou transfert thermique? Dans un monde où il existe une grande variété d’imprimantes, de supports et de technologies d’impression, l’interaction entre eux affecte très probablement la conservation à long terme des étiquettes dans l’environnement chimique du fluide de conservation. Dans les collections en fluide, les principaux problèmes fréquemment rencontrés avec les étiquettes sont la délamination, l’abrasion, la décoloration et la désintégration lors de l’immersion dans des solutions telles que l’éthanol et le formaldéhyde (ou formol). Très peu de publications ont présenté des procédures de test évaluant le comportement et la stabilité des étiquettes imprimées, immergés dans les solvants utilisés dans les collections en fluide. Cet article présente une série d’expériences mises en place dans les collections nationales d’Histoire naturelle de l’Université hébraïque de Jérusalem (NNHC-HUJ) pour tester diverses étiquettes de musées. Les tests ont permis de comparer les étiquettes réellement utilisées dans différentes collections d’Histoire naturelle, et comprenaient des étiquettes provenant d’imprimantes à transfert thermique et à jet d’encre. Toutes ont été soumises Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 vessel in a fluid-based collection. One major deviation from the usual Oddy test procedure was the duration of the test. Regular Oddy tests usually cover 28 days (Beiner et al. 2015). After consultation with chemists and based on the results of Experiment 1, chemical analyses delivered results on the anticipated changes within hours; thus, prolonged testing for 28 days would not have contributed more data on the performance and damage of printed labels in this study. As noted by A. Bentley (University of Kansas Biodiversity Institute, pers. comm.), the test conditions were very harsh and well outside the normal operation conditions of fluid-based collections. Such collections are maintained at much lower temperatures in standard practice, and the occurrence of abrasive forces— other than a presumed very slow abrasion along label edges over long periods of time—is rare, generally being a factor only outside of museum storage conditions when specimens in jars are transported from the field or shipped between institutions. In addition, it is important to bear in mind that different printers, label substrates, and inks may not yield similar results when subjected to the same conditions. Similar testing with accelerated aging experiments under the conditions described above is easy to perform in many collections and may be a valuable tool for the basic evaluation and assessment or the performance of (new) labels. Whenever possible, chemical analyses can add valuable insights, and the results of the chemical analyses in Experiment 1 are relevant beyond the mere evaluation of traditional storage conditions. For example, evidence of the release of chemical components into the solution clearly advocates against the use of internal labels for DNA sampling and for long-term storage in tissue collections, as released chemicals could potentially interact with the DNA molecule and may induce (chemical) damage or degradation to samples stored in highly concentrated ethanol. 2020 BEINER—LABELS FOR ETERNITY 113 à un vieillissement accéléré et à une abrasion mécanique. Dans notre série de tests, les étiquettes à jet d’encre ont donné les meilleures performances. LITERATURE CITED Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/34/1/101/2922042/i0831-4985-34-1-101.pdf by guest on 07 October 2021 Beccaloni, J. 2016. The curation of Arachnida collections in alcohol: An international survey. Collection Forum 30(1–2):96–110. Beiner, G.G., M. Lavi, H. Seri, A. Rossin, O. Lev, J. Gunn, and R. Rabinovich. 2015. Oddy tests: Adding the analytical dimension. 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