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!
Ms. Chui presented a truly gorgeous Renaissance painting that came from the Budapest Museum of Fine Arts to the J. Paul Getty Museum for a collaborative research and conservation project. Immediately it was clear that the style was recognizable as influenced by Leonardo da Vinci. This was probably the reason for the misattribution in the 18th century and earlier. With an array of beautiful photography comparing various paintings art historically, the very convincing case was made for the current attribution to Giovanni Antonio Boltraffio, a student of Leonardo in his workshop in Milan at the turn of the 16th century.
Extensively but not expertly previously restored, Ms. Chui unraveled the condition of the panel painting layer by layer with excellent documentation from the international team that worked on this project. Each layer of discovery added further proof to Boltraffio’s authorship.
In fact, it seemed to me that the research and documentation discovery process on this painting must add to the collective knowledge on Leonardo’s techniques and teachings. Adding to that body of knowledge is always an exciting prospect. It was wonderful to see the evidence that Ms. Chui presented of the master’s hand in the manufacturing process and the design work. Specifically, I found the discussion on original fingerprints left behind in the imprimatura layers interesting, though no conclusion was insinuated that they were definitely by Leonardo.
While none of the conservation treatments were innovative, they were most interesting, well photographed and pleasantly presented. As you might expect, the quality of the conservation work resulted in maximizing the original beauty of a truly unique and beautiful image of this holy mother and child. It made for excellent technical entertainment much the way I found myself eagerly awaiting, back in the day, the arrival of the latest National Gallery Bulletin. Detailed, colorful cross sections, exceptional and easy to understand diagrams to clarify, photographic references and ties to other works of art and the fluid manner of Ms. Chui made this a 1st class presentation.
If you missed this presentation, then I’m sorry but it is impossible to do the material presented justice in this blog post. We can only hope that Ms. Chui publishes her material accompanied by all of the slides of her powerpoint (doubtful). Visually, it’s a great presentation but, in addition, the info needs to be searchable and referenced by others.
Contact Ms. Sue Ann Chui at firstname.lastname@example.org and (310) 440 7023
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Scott M. Haskins
Fine Art Conservation Laboratories (FACL, Inc.)
(805) 564 3438