• Oil Paint

  The Effect of Pigments on the Drying of Oil and Alkyd Paint

  Posted by George O'Hanlon on August 13, 2020 at 8:20 pm

  The results of studying the effect of pigments on oil and alkyd paint films obtained from a long term study can be summarized as follows:

  • The early drying of oil paints is due to autoxidation, but it does not necessarily result in a tough, durable film.
  • The later film-forming processes are largely the result of metal ions from pigments, added driers, or even contamination from other materials inducing cross-linking and polymerization.
  • Not all pigments contribute to the development of good paint films, and some, such as zinc oxide, can actually have detrimental effects, causing brittleness and even delaminating the paint layers.
  • Without pigments supplying “active” metal ions, film formation in drying oils is poor.
  • Different pigments have dramatically different effects on film formation and the durability of both oil and alkyd paints.
  • Mixing paints made with active pigments can increase the durability of paints with less active pigments.
  • One layer of paint in a painting can affect other adjacent layers both positively and adversely. The paint chosen for the ground layer can affect the long-term stability of the painting.

  The chart below shows how the mechanical properties (flexibility) of basic lead carbonate ground in cold-pressed linseed oil continues to get stiffer and stronger after 18.75 years of drying.

  Source: Marion F. Mecklenburg, Charles S. Tumosa, and Edward P. Vicenzi. (2012) “The Influence of Pigments and Ion Migration on the Durability of Drying Oil and Alkyd Paints”. Smithsonian Contributions to Museum Conservation. No. 3. pp. 59-67. Download

  

  • This discussion was modified 3 years, 9 months ago by  George O'Hanlon.

  George O'Hanlon replied 3 years, 9 months ago 1 Member · 0 Replies
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