Aging
To see how changes over time affect the valuation, the RCE created a Photoshop simulation of the digitised object, based on the expected light sensitivity. In the simulation, reproductions tolerated the least light. With the diazotype, the lines soon faded completely, and the blueprint fades with a shift to purple. As long as the characteristic features remain intact, such as the lines of the diazotype and the blue colour of the blueprint, the decay does not greatly affect the usefulness or value of the material.
When asked about a strategy for showing the copies, the group initially chose to rotate the different versions. When it became clear that the consequence would be that all the versions would deteriorateAgnes Brokerhof, Pieter Kuiper & Steph Scholten (2018) Spread or Sacrifice: Dilemma for Lighting Policies, Studies in Conservation, 63:sup1, 28-34, DOI: 10.1080/00393630.2018.1504439, the consensus changed. One choice isn’t necessarily better than the other, but it’s good to establish the tipping point from acceptable to unacceptable change.
Also interesting is the drawing on vellum, in which the browning of the medium can increase the sense of age and historical experience. The lines of the ink and graphite will hardly change under the influence of light. There is a slight reduction in contrast, but it has little effect on readability and value over the years.
Light will have relatively little effect on the gouache coloured drawing. Earlier researchLuc Megens, Rika Pause, Mariel Polman, Onderzoek van de pigmenten in de kleurontwerpen van Theo van Doesburg voor de Aubette in Straatsburg, [Investigation of the Pigments in the Colour Designs of Theo Van Doesburg for the Aubette In Strasbourg,] Cultural Heritage Agency, November 9, 2019 on a comparable work showed that Van Doesburg used paints with fairly light-fast pigments. The poor adhesion of the paint to a surface that is actually unsuitable and which will eventually yellow is actually expected to cause more damage. Paint loss is unacceptable according to the group. This work would therefore not be currently suitable for consulting or exhibiting, but would first have to be conserved.