Course Leaders: Thea van Oosten, former senior conservation scientist at the Cultural Heritage Agency of the Netherlands (RCE) since 1989, currently retired and freelancing and Anna Laganà, lecturer at the University of Amsterdam and freelance conservator / researcher specialized in the conservation of plastics. Both were entertaining educators throughout the course.
This is a short review of the above plastics workshop which took place as a collaborative professional development program between the University of Amsterdam and the Cultural Heritage Agency of the Netherlands (RCE). The four day course combined theory and practice, as well as input from the ten participants from seven countries regarding the challenges they are encountering with plastics materials.
An overview of the development of plastics from the 19th century to present day was reported including the chemical properties and manufacturing processes which create the various types of plastics materials. This was useful in determining what type of plastics you may be working with and how this influences degradation and therefore future preservation protocols. Understanding the difference between three main characteristics of thermoplastics, thermosets and elastomers and their polymeric makeup made sense when thinking about characteristics and deterioration patterns. The impact of additives, such as fillers, pigments and plasticizers used to manipulate the properties of plastics materials can have drastic effects on the aesthetic aspect, touch and life span of many plastic objects. These are considered the internal factors that gear the longevity of synthetic materials. External factors like oxygen, ozone, light and temperature cause oxidative degradation and hydrolysis of plastic objects initiating catalytic reactions and can accelerate deterioration. Scary stuff! But in the safe hands of Thea and Anna we motored on.
The five most vulnerable plastics: cellulose nitrate, cellulose acetate, poly (vinyl chloride), natural rubber and polyurethane were highlighted. These plastics are known to show significant deterioration patterns in short periods of time. Chemical breakdown, physical and mechanical damage and also, biological damage are often documented with these kinds of plastics. Theory sessions encompassed plenty of handling sessions using examples from reference collections donated to the RCE by Thea van Oosten. This exercise helped to familiarize participants with various plastics materials produced through history by feeling, smelling and listening to the sound plastics make when dropped. Density and color were other considerations. Film clips of manufacturing processes and artists using and manipulating plastic products to produce works of art were shown.
Ron Mueck – videos: https://www.youtube.com/channel/UC4tUoKVLJ8j6onJ2C5ytdGQ
Practical sessions included the impact of solvents on various plastics types. Deionized water and white spirit (organic clear solvent made with a mixture of hydrocarbons) seemed to have the least effect, whereas acetone showed significant physical change. Great fun was had examining residual strains in clear and translucent plastics using a strain viewer. This instrument provided a fabulous myriad of colors which enabled the examiner to measure the internal stress areas. Learning adhesive and consolidation methodologies provided good pragmatic solutions to repair and stabilize plastic objects that are physically or mechanically damaged. Understanding surface energy of plastic surfaces (low energy a water droplet will remain on the surface, high energy the water droplet will disperse evenly) was useful to know when thinking about adhesion levels and prevention of causing further internal stress and strain. There was dedicated sessions to the specific properties and consolidation of polyurethane foam as this material can degrade quickly depending on its polymeric make-up. Cleaning strategies were reviewed and practical sessions included the effects of dry cleaning methods, solvents and mild detergent solutions on various plastics materials.
Preventive guidelines were discussed; display parameters of 50- 150 lux (5-14 foot-candles), dark conditions preferred in storage, 50%RH, a temperature of 18-20 centigrade (64.4-68 Fahrenheit), good ventilation to prevent a build-up of gaseous degradation products from off-gassing plastics and maintaining a low temperature to help slow down the degradation process. Oxygen scavengers were mentioned as a useful product to help maintain a good environment. Encapsulating rubber objects was also demonstrated in order to slow down the deterioration of rubber being one of the most vulnerable plastics.
All participants were provided with a folder with useful theory, a bibliography and documentation of the presentations that were given during the course. One of the most useful sections for me were the tables reflecting the solubility parameters and chemical resistance of plastics, these would certainly help when deciphering appropriate cleaning systems if appropriate at all. I would certainly consider the use of micro emulsions and gels as other applications which were not included in the workshop. Also, the data sheets referring to adhesive properties and their appropriateness to various plastic types would be a good reference point to selecting adhesive and consolidation treatments. All provided good starting points for investigation.
With many thanks to Thea and Anna, they were both marvelous!
The Essentials of Inpainting workshop was well attended and greeted by a very welcoming James Bernstein adorned in wonderful kilt regalia. The one day workshop was presented predominantly through power-point presentation with plenty of interaction and discussion with the participants. The main head table was packed with portable workstation blocks holding a huge array of color pigments. The workstations were made from Ethafoam® and were light-weight and versatile. Examples of fillers were also available to examine which emphasized the essence of choice and considerations when thinking about filling and inpainting surfaces.
The day focused on practical application rather than ethical considerations due to time limits and varying contexts that conservators work within. A great booklet full of useful handouts which echoed the content of the presentation was provided from the start which helped prevent excessive note taking and increased knowledge transfer throughout the day. The booklet provided a summary of the content of the workshop; materials, concepts and participants experiences which included preparation, techniques, varying reactions of the choice of media, brushes, study of pigments, paints and their properties, toning and patination and in-painting standards. Complementary material relating to the presentation was included which was thorough in content which really helps with later revision.
James reminded the delegates of the importance of establishing a sense of the character of the object and all layers beneath the paint film need to be evaluated as all these elements effect one another. When thinking about inpainting, wicking and capillary actions need to be controlled and identifying inherent and altered states needs to be deciphered. These were just many of the considerations taken into account when trying to approach inpainting on various surfaces. Good support during treatment application was considered essential to enable good control. Painting sticks, plexi blocks and rolls were other alternatives if working with other substrates. Having a well organized and labeled pigment selection was highly recommended along with strong light and magnification.
Fill material and techniques were discussed and the importance of isolating areas requiring infilling to reduce the risk of leeching of binders. James spent a lot of time explaining the varying techniques to apply fill material to enable good inpainting. I particularly enjoyed learning about the use of cellulose fibers as they were compatible with cellulose materials such as canvas, paper and other organic objects. The material is inert and is easy to remove. Solka-Floc® was used as an example of Microcellulose Purified Cellulose fibers available in varying fiber lengths which can be used with the adhesive/consolidant of your choice. Differing techniques regarding reversibility of inpainting was also discussed such as how the Getty Conservation Institute use tissue overlays as an isolating method and as a form of reversibility. Drying time and shrinkage of fill material was considered an issue; if the fill is not applied well they have a tendency to sink in the center due to the material drying from the outside in, leaving the center to dry last. Applying the fill as thickly as possible will aid in less shrinkage, which is another common challenge with fills. James explained the effects of fill materials on inpainting through a failed project he had completed some time ago which highlighted how an incorrect fill could be detrimental to the inpainting applied. This was a great lesson. James presented all kinds of techniques with regards to good lighting, burnishing and smoothing.
Color and pigments were reported which led to a reminder of the color theory and pigment indexing. It was rather rewarding as a textile conservator to learn James is more fearful of dyes than pigments which really emphasized the complexity of dyed textile substrates in comparison to the complexities of pigmented paint film. The potential for dyes to migrate and bleed is a very real one and control can be difficult. Refraction and transmission of light were covered, as were issues surrounding whites, inerts pigments and black pigments. These can be difficult pigments to manipulate and a comprehensive pigment and particle chart was supplied which included health concerns.
The session progressed onto binders and polymers and the effects of low and high molecular weights with regards penetration. James advised to always check the composition of pigments, just because pigments have been selected for conservation use, it does not mean it is safe. Building up color slowly is essential to help with replication.
When first I realized the amount of information which was being packed into this one day workshop I thought the day would be too overwhelming. I was pleasantly surprised as to how much I actually understood due to the steady and consistent pace James presented his expertise. The handbook was incredibly comprehensive and James is very approachable as an instructor, both not just essential to inpainting but to training and developing.