Walnut oil

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.

• 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

• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000