Walnut oil

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Description

A natural, colorless drying oil pressed from the nuts of a Walnut tree, Juglans regia. Walnuts contain approximately 65% oil. The cold-pressed oil is pale yellow while the hot-pressed oil has a green tinge. Walnut oil dries slower and yellows less than Linseed oil, but it dries faster than Poppy seed oil. It was popular as a paint medium in Italy, the Netherlands, and Germany. Walnut oil will turn rancid and develop a strong odor on storage.

Synonyms and Related Terms

nut oil; aceite de nueces (Esp.); huile de noix (Fr.); olio di noce (It)

Risks

Turns rancid and develops a strong odor on storage.

Physical and Chemical Properties

  • Liquid is soluble in ethanol, ether, chloroform, turpentine, carbon disulfide.
  • Saponification number = 188-197
  • Iodine number = 140-150
  • Acid value = 2.5
  • Density = 0.919-0.927
  • Refractive Index = 1.477-1.480
Content of Fatty Acid of the Drying Oil after Hydrolysis (Phenacyl Bromide Esters % w/w Total Fatty Acid) (from Tarola et. al 2012)
Drying oil Linolenic acid
C18:3 % ± SD
Linoleic acid
C18:2 % ± SD
Myristic acid
C14:0 % ± SD
Palmitic acid
C16:0 % ± SD
Oleic acid
C18:1 % ± SD
Stearic acid
C18:0 % ± SD
Linseed oil 58 ± 1.2 16 ± 0.8 7 ± 1.1 16 ± 1.8 3 ± 0.1
Walnut oil 8 ± 0.3 72 ± 1.5 6 ± 0.6 12 ± 1.1 2 ± 0.2
Poppy seed oil 8 ± 0.7 70 ± 0.8 9 ± 0.5 10 ± 0.4 3 ± 0.2

Resources and Citations

  • Tarola, A.M., A.M. Girelli, S. Lorusso, "High Performance Liquid Chromatography Determination of Fatty Acids in Drying Oils Following Lipase Action", Journal of Chromatographic Science, Vol. 50(4), April 2012, Pages 294–300.
  • Mills J.. "Composition and identification of dried oil film: The gas-chromatographic examination of paint media", Studies in Conservation, 1966, vol. 11 (pg. 92-106) Part I. Fatty acid.
  • M.Serpico, R.White, "Oil, fat and wax" in Ancient Egyptian Materials and Technology, P.Nicholson, I.Shaw (eds.), Cambridge University Press, 2000, p. 390-429.
  • Thomas Gregory, The Condensed Chemical Dictionary, Reinhold Publishing, New York, 3rd ed., 1942
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
  • R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
  • Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
  • Reed Kay, The Painter's Guide To Studio Methods and Materials, Prentice-Hall, Inc., Englewood Cliffs, NJ, 1983
  • Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980

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