Damage Atlas Glossy Surfaces

Conservation guidelines

These guidelines have been developed based on testing conducted during the Glossy Surfaces project. Ongoing research is being carried out to explore additional preventive conservation methods, and this document will be updated as new insights are gained.

The first step in preventive conservation is identifying the type of coating present on a specific item in the collection. Coatings on textiles and leathers can be composed of various materials such as polyurethane, poly(vinyl chloride), polyacrylates, and more. Identification of the coating can be achieved through small tests like the Beilsteintest, which can determine if it is PVC, while analysis with techniques like FTIR (Fourier-Transform Infrared spectroscopy) can provide definitive results. The substrate and any intermediate layers can be visually examined using microscopy. If you are certain that you are dealing with a TPU (thermoplastic polyurethane) coating, the following guidelines can help in preserving your object for a longer period.

For synthetic materials, commonly referred to as plastics, it is recommended to store them separately from other items in the collection. This not only protects other non-plastic objects in case of off-gassing from the plastic items, but it also allows for more frequent and close monitoring. This is particularly important because several types of synthetic materials in collections can undergo severe degradation in a short time, as is the case with synthetic coated fabrics.

Determining specific issues with the collection item:

The Glossy Surfaces project conducted research on various packing materials for storing synthetic coated fabrics. Different museum and archive storages were visited to gain a better understanding of existing packing solutions and the issues associated with these materials. Additionally, artificial aging tests were performed to compare the performance of packing materials in direct contact with the coatings and test samples in anoxic enclosures. Details of this aging test are explained below, and the resulting guidelines were developed based on these tests. Further artificial aging tests and natural aging tests in storage are planned for the future.

 Artificial aging with relative humidity (RH) and temperature (T):

A selection of TPU-coated samples, varying in color, thickness, substrate, and overall stratigraphy, was chosen for representativeness. These samples were tested with promising packing material options to find the best storage solution. The tests included both packed and unpacked samples, with the latter serving as reference samples to better understand the impact of the selected packing materials.

The artificial aging test was conducted in two series. In the first series, the samples were aged under extreme conditions to accelerate the aging process, according to ISO 1419-C at 70°C with 95% RH for 7 days, also known as the "jungle test." After this test series, a few packing materials were excluded and further testing was done with the most promising options. Secondly, the samples were subjected to ASTM F1980 oven tests for 76 days at a temperature of 55°C and a relative humidity of approximately 7% in the first 38 days and approximately 75% in the second 38 days. The samples were characterized before aging, after the first part of the aging test, and after the second part. Characterization methods included visual assessment with detailed descriptions, macro and micro imaging using a Dino-Lite microscope, gloss measurements, and molecular analysis using Attenuated Total Reflection Fourier-Transform InfraRed spectroscopy (ATR-FTIR).

Tested storage materials:

• Tyvek
• Tissue paper
• Cotton
• Uncoated Melinex (a PET foil)
• Silicone-coated Melinex (a PET foil with a thin silicone layer)
• Glass
• Silicone-coated paper (paper with a thin silicone layer)
• Anoxic environments with RP System Type-K Oxygen Absorbers
• Anoxic environments with ATCO FTM 1000 Oxygen Absorbers
• Anoxic environments with ATCO FTM 1000 Oxygen Absorbers and silica gel

 

Recommendations

 

The following recommendations are based on the information gathered from the museum and archive storages visited, as well as the artificial aging test conducted during the Glossy Surfaces project. A detailed table with the advantages and disadvantages of different packing materials can be found below.

 

Before considering the use of any suggested materials, carefully examine your object and identify any existing issues or damage patterns. Minimize direct contact between the packing material and the object, especially if the coating is already showing signs of tackiness. If possible, store the object in a standing or hanging position. Ensure that the object is adequately supported from the inside to maintain its shape. Keep in mind that the degradation process may alter the appearance, shape, or mechanical properties of the item and preserve the object's 3D shape to facilitate display. When handling TPU coated objects, always use nitrile gloves to avoid leaving permanent fingerprints, particularly in cases of blooming or tackiness.

 

 

 

Martin Margiela jacket image Frederik Vercruysse 

 

Packing materials that are not suitable for TPU coatings and should never be used.

 

Polyethylene foil

As seen in different collections, PE foil has proven to be highly problematic for both short-term and long-term storage of TPU coated fabrics. Polyethylene foil bags around collection items create a microclimate that traps moisture. In most instances, there was adherence between the coating and packing materials, leading to the separation of the coating from the substrate and subsequent losses.

 

Tyvek

During the visits at the collection partners, tyvek proved to be highly problematic for TPU coated fabrics in long term and short term storage. Tyvek was commonly employed as a covering material for hanging collection items, as well as a packing material for flat-laid objects. It was also used to provide protection between pockets, sleeves, or buttons. The ‘jungle test’ gave very similar results as to what can be seen with real-life aging and was excluded from further testing. Two major issues were identified, the TPU coating caused staining on the Tyvek material, resulting in discoloration. Secondly, the coating started to adhere to the Tyvek, leading to significant detachment of the coating from the underlying substrate, ultimately resulting in the loss of material.

 

 

Tissue paper 

During the visits to museum and archive storages, the use of tissue paper as a packing material inside boxes was frequently encountered. It was found to be highly unsuitable for direct contact with TPU coatings, and as a result, it was also excluded from further testing after the initial 'jungle' test series.

Similar to Tyvek, tissue paper exhibited staining when in contact with TPU coatings, and in many cases, it completely adhered to the coating, leading to detachment from the substrate. However, it can still be used inside objects to provide support if those particular parts do not contain TPU coatings.

Glass

During the artificial aging tests, all TPU-coated samples became adhered to the glass. However, no comparable instances of this were observed in real-life scenarios. As a result, it is currently not advisable to use TPU coatings for storage purposes until further testing can be conducted to assess the effects of natural aging in storage conditions.

 

Melinex

Melinex or similar PET foils are commonly utilized for storing collection items either flat or in boxes. However, based on observations in collection storage and artificial aging tests, it is evident that uncoated Melinex, like the previously mentioned materials, is not recommended for the storage of TPU coatings. This is due to the adhesion of the coating to the Melinex, resulting in detachment and potential material losses.

 

Anoxic enclosure with ATCO or Ageless

ATCO and Ageless are similar oxygen absorbers that are both known to raise the RH inside the anoxic enclosure to undesirable levels, leading to microclimates that are difficult to control. Although relatively inexpensive, these oxygen absorbers are not recommended as a suitable option for the long term storage of TPU coatings.

 

Packing materials that might be suitable for TPU coatings, however with caution and they are not really recommended. 

 

Cotton (prewashed) 

Cotton is commonly employed as a protective cover for hanging collection items in long-term storage, serving as a barrier against dust. While cotton caused minimal damage to the TPU-coated samples in the artificial aging tests, its long-term safety for these materials remains uncertain. During visits to partner storages, instances were reported where cotton adhered to the TPU coatings. Nevertheless, when compared to other cover materials like PE foil or Tyvek, cotton is considered the safest option.

 

To conduct further testing, new case studies will be packed and stored under museum conditions to undergo natural aging tests. The results obtained from these tests will be compared with the artificial aging results and subsequently updated in this damage atlas.

 

Silicone coated melinex

Silicone-coated Melinex is commonly utilized as a preventive measure to avoid the adhesion of coated collection items to themselves or surrounding materials, such as armpits, pockets, and other contact points. Unlike uncoated Melinex, the silicone layer acts as a non-stick layer, minimizing damage by preventing detachment of the coating from the substrate. Additionally, the transparency of the silicone-coated Melinex facilitates easy monitoring of the object with minimal manipulation. In theory, this material appears to be ideal for packaging TPU-coated objects.

However, during the artificial aging test, a notable visual change in the surface structure was observed on several samples. This change resulted in an increased gloss when compared to both the unaged samples and the aged samples that were not packed with silicone-coated Melinex. Moreover, some collection items stored using this material exhibited surface changes in specific areas, as evident in the images below.

 

In further testing, the water permeability of silicone-coated Melinex was examined, revealing a remarkably low water vapor transfer rate. It is a relatively impermeable material, potentially leading to the entrapment of humidity within the packaging. This, in turn, could create a microclimate for TPU-coated fabrics, which are susceptible to hydrolytic degradation. Consequently, the use of silicone-coated Melinex is not fully recommended. However, if its use cannot be avoided, it should be employed with caution and subject to regular monitoring.

To gain better insights, additional natural and artificial aging tests will be conducted to delve deeper into this matter. The results obtained from these tests will be subsequently updated in this damage atlas.

 

Packing material that seems to be suitable for TPU coatings and all gave promising results, based on preliminary results. (Further testing is still being carried out) 

 

Silicone coated paper

In collection storages, silicone-coated paper is frequently used in a similar manner to silicone-coated Melinex. During the artificial aging test, the silicone-coated paper demonstrated positive results by not adhering to any of the tested samples. This suggests that the material may be suitable for the storage of TPU-coated fabrics, and its use is recommended to prevent the coatings from coming into contact with each other and other surfaces, such as acid-free boxes or drawers.

 

However, it is not advisable to completely enclose objects between layers of paper, as this can potentially create a microclimate.

 

Anoxic enclosure with RP System Type-K Oxygen Absorbers

The results of the low-oxygen storage in an artificially aged environment were inconclusive due to the test being conducted at the recommended temperature limit for the absorbers to function effectively. However, prior long-term low-oxygen storage experiments were conducted by MoMu and the Met using this type of absorber. At MoMu, a coated object was packed in 2012, repacked in 2017, and stored until 2022. Although the degradation was not completely stopped, it was significantly slowed down.

It is crucial to measure the oxygen level annually. Typically, after a period of 5 years, the object should be repacked. When doing so, it is advisable not to open the package entirely. Instead, puncturing a small hole and allowing it to rest for 24 hours is the preferred method.

One advantage of using these oxygen absorbers is that anoxic enclosures can be created by museum staff. However, the downsides include the high cost of this packing method and the limited accessibility to the object itself.

A formula is required for determining the necessary materials. Measure the dimensions of the required enclosure in centimeters (Length x Width x Height) to obtain the total volume in cubic centimeters (cm³). Next, convert the volume to liters, and then divide the total volume by the size of the packet to be used.

Anoxic enclosure with Argon gas

Flushing the packaging with argon gas creates an optimal environment, making it well-suited for long-term storage. It is recommended to repeat the flushing process with argon gas every 3 years. This method was tested at the MET, and it resulted in minimal visible changes to the object. While this packing method shows great promise, the drawback is that most museums do not have the capability to perform argon gas flushing in-house. Instead, they need to rent specialized equipment or rely on specialist companies, which gives additional costs.

 

Recommended climate conditions

 

A stable climate is highly recommended, preferably a drier and colder environment since higher temperatures can accelerate the degradation process and the most commonly found coatings are prone to hydrolysis. 

 

Recommendations: 

• Relative Humidity: 40-50%, fluctuations +-2.5%;
• Temperature: 14-18°C, fluctuations +-1°C. 
• Licht no more than 50 Lux in display and in storage as dark as possible. 

 

In conclusion: Please be aware that the conservation of TPU, and plastics in general, is still a relatively new area and knowledge of preventive conservation is evolving constantly. Further testing is necessary, given the complexity of this polymer and its combination with textiles. The most important guideline for TPU coatings is that monitoring the objects is crucial. A frequent check every 3-6 months of the coatings is well advised. Even with the suggested packaging materials, a follow up of your object is important. At one point the degradation process starts and it is very difficult to stop it. Many objects remain as sleeping beauty’s in collections. As conservators, our mission is to slow down the passage of time and preserve these precious collections.

Table

 

Damage atlas for TPU 

 

Number of degradation stages based on the Manchester Triage color chart. 

 

 

Type of collection researched:

Surface types: 

mat - semi gloss - gloss

TPU Types:

TPU Ester aromatic -TPU Ether aliphatic - TPU ester aliphatic - TPU ether aromatic 

Substrates:

Cotton - Silk - polyester - polyamide - 

Material structure of TPU:

film - fibre - coating 

Decades:1960-2020

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