Resistance of Paraloid B-72 to Temperature and UV Radiation

Author: Nađa Šperac
Mentors: Professor Branko Matulić, PhD; Lecturer Nikola Radošević; Assistant Professor Ivica Ljubenkov, PhD

Arts Academy, Split (Croatia)
Study programme: Integrated undergraduate and graduate course of study in conservation-restoration
Specialization: Wall paintings and mosaics (5th year of study)


Sperac NParaloid B-72 is the thermoplastic, non-yellowing, synthetic resin. Its chemical composition is copolymer methacrylate and ethyl methacrylate. Due to its chemical stability, reversibility, and good aging characteristics, Paralod B-72 has found wide use in conservation as a consolidant, adhesive, insulator and varnish. It is compatible with almost every material.
A previous research has proved Paraloid B-72’s smaller or greater vulnerability to microorganism attack, depending on the solvent used. Taking into consideration this and many other researches, it was decided to investigate Paraloid B-72's resistance to high temperatures and UV radiation.
The research will use the analytical method of thermogravimetry, which is normally employed in the characterization and identification of materials, determination of organic contents in materials as well as in – for us here particularly interesting – the investigation of material degradation mechanisms.
There will be four different samples, each consisting of a layer of lime plaster, a pigment layer, and a layer of Paraloid B-72 used in the following concentrations:

  1. 3 % – the concentration which is generally used for consolidation purposes/ as a consolidant,
  2. 7 % – according to foreign articles, the most widely used concentration when it is employed as insulator, varnish, etc.
  3. 10 %
  4. 50 % – the common concentration of Paraloid B-72, when used as an adhesive.

It was agreed that it would be interesting to check its resistance to temperature and reversibility in these concentrations. Therefore, it is planned to expose the samples continuously for three months to the following temperature values:

  1. 35 °C – the temperature chosen according to the Tg, which is between 30 and 40 C,
  2. 45 °C – the temperature, which is slightly above the Tg values of Paraloid B-72,
  3. 50 °C – the maximum temperature that a facade can reach in the summer period,
  4. 80 °C – this extreme temperature was chosen as the ultimate endurance test.

The tests of Paraloid B-72 susceptibility to UV radiation require simulation of weather conditions during the summer months when the UV index is high. Two groups of samples will be prepared for this research. The first one will consist of a layer of lime mortar, a layer of blue pigment, and a layer of Paraloid B-72. The second one will contain all of the above, except that the blue pigment will be replaced with green pigment. Both samples will be prepared using a secco technique. They will be continuously exposed to UV radiation for the specific period of time, which will reveal the endurance of Paraloid B-72 and its ability to protect extremely sensitive green and blue pigments.
This research results will be relevant for exterior wall paintings, stucco and sgraffito decorations, all of which get exposed to high temperature and UV radiation in Mediterranean summer weather conditions.

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Short biography

NAĐA ŠPERAC was born in Split, in 1989. After having studied photographic design at the secondary school of fine art, she was admitted to the Arts Academy, Split. She is currently a fifth year student of an integrated undergraduate and graduate course of study in conservation-restoration. Nađa specializes in conservation-restoration of wall paintings and mosaics.