We are often asked about the use of clove oil to retard the drying of oil paint. Like many others, you may have heard that it darkens upon exposure to light. This information appears to be from Marion Boddy-Evans at About.com—Painting (now Thought Co.):
Marion posed the question to an expert, Paul Robinson, Technical Advisor at Winsor & Newton, who said:
“Clove oil works well as a retarder but there is a note of caution: over time (a long time) it does actually darken as it dries. It starts off nice a light but can eventually turn black. This is over years and is dependent on the amount of direct light. I would be tempted to use a different oil as a retarder—linseed or stand oil—and if my tubes go solid I would revive these with solvent and oils.”
Whether the darkening of clove oil will affect an oil painting is not clearly understood. One artist, Kyle Surges, prepared test panels with oil paint containing clove oil and without clove oil. After several years he visually compared the paint samples. The paint samples with clove oil did not appear to show any difference in color from the paint samples that did not contain clove oil. You can see the test results on his blog, The Nitpicky Artist.
Although the claim clove oil darkens, paint has not been proven, using clove oil as a drying retarder in oil paint is greatly discouraged as its addition may substantially weaken the dried paint film. The use of clove oil in oil painting was also asked on the forum managed by the University of Delaware, Materials Information and Technical Resources for Artists (MITRA). Kristen deGhetaldi answered the artist:
“Every so often we will encounter a painting by an artist who is known to have used clove oil or a painting that lists clove oil on the reverse as an ingredient in the paint. Many of these paintings have proven impossible to safely clean, meaning the yellowed, degraded varnishes used to coat the surface cannot be removed without causing irreversible damage to the paint layer. Clove oil is an attractive additive BECAUSE it hinders drying...but adding too much can create a film that remains sticky and does not form a cohesive, healthy paint film, one that will remain sensitive to even the mildest of solvents. Most likely adding a drop or two to a substantial amount of medium is not the end of the world, but artists often add far more than is necessary in order to combat the drying processes.”
MITRA Forum Question
More effective ways of retarding the drying of oil paint are to use poppy seed oil or safflower oil. Some artists use clove oil to prevent oil paint from skinning over on the palette. Rather than adding clove oil to paint, one practice is to place your palette in a plastic container, such as a Sta-Wet palette, or under a cover, such as those used to cover dishes in a microwave oven. Saturate a cotton ball with clove oil, place it alongside your palette, and enclose it. Clove oil is primarily composed of eugenol, which is an antioxidant. This will slow the oxidation rate of the oil paint and help keep it fresh for painting much longer.
Some may regard this practice as possibly damaging to oil paint, but Dr. Chris Petersen, a retired organic chemist who formerly worked at Dupont, suggests otherwise on the MITRA Forum:
“There would be minimal penetration of the vapor if the paint is simply exposed overnight; clove oil is a phenolic type antioxidant with a boiling point >250 deg. Surface penetration is actually what you want if you are trying to prevent the drying effect that is propagated by oxygen promoted free radicals. The stuff does have a strong odor so even a small amount in the air is overwhelming. As an interesting aside, phenolic antioxidants are used to stabilize acrylic monomers like methyl methacrylate so they can be shipped and stored in bottles. When you add an initiator to make a polymer, the inhibitor is consumed and the free radical reaction occurs.”
So, in summary, there would be some penetration, albeit minimal. Dr. Petersen, therefore, believes that this would not drastically impact the “health” of the paints in the immediate future.
Clove oil is a colorless or pale yellow oil derived from the clove tree cultivated in the Moluccas or Spice Islands (now Maluka of Indonesia), Madagascar, Zanzibar, and the Philippines. The principle component of clove oil is eugenol. It is very slightly soluble in water and soluble in organic solvents. It has a spicy aroma and the taste of cloves. It is used in perfumes, flavorings, essential oils, and dentistry (as a local antiseptic and analgesic).
Rublev Colours clove oil is obtained by redistillation of crude clove leaf oil obtained initially by steam distillation of the dried leaves from cultivated non-GMO clove trees. The oil is pure and natural, and unadulterated. Raw materials and processed oil were never irradiated. The oil was never tested on animals. Analysis of the clove oil shows that the main component of the oil is eugenol, with a concentration of 85%. Eugenol is a natural antioxidant that prevents or slows the rate of oxidation of vegetable oils.
Uses in Painting
A drop or two of clove oil can also suppress the odor of turpentine, and even this small amount can give a pleasant odor.
Clove oil is also used as a preservative in water-based painting mediums, such as casein, egg tempera, glue (distemper), and watercolor. Add a drop to 100 ml (3.3 ounces) of the paint medium, for example, to preserve the paint.
Origin and History
The Latin word clavus means nail shaped, which refers to the bud of the clove tree since the shaft and head resemble a nail. The clove tree (Syzgium aromaticum or Eugenia caryophyllata) is a tropical evergreen tree believed to be indigenous to the Moluccas. The people of the Moluccas used to plant a clove tree to celebrate the birth of a child and would wear a necklace of cloves as protection from evil spirits and illness. As early as 200 BCE, envoys from Java to the Han-dynasty court of China brought cloves with them to China. The Chinese used it to relieve toothaches and as a breath freshener, especially during audiences with the emperor. Clove was much used by the Greeks, Romans, and Chinese for its medicinal value. Clove has antiseptic properties and was used to prevent contagious diseases like the Plague. During the Middle Ages, cloves were used in Europe to preserve, flavor, and garnish food. From the 8th century, cloves became increasingly popular in Europe, and along with nutmeg, the importation of this coveted spice helped the enterprising Venetians become extraordinarily wealthy. The lure of cloves and nutmeg attracted the Portuguese to the Spice Islands in 1514; they were followed by the Dutch in 1605, who retained control over the trade until late in the 18th century, at which time the exotic spices of the Moluccas were starting to be grown elsewhere in the world. Clove cultivation was almost entirely confined to Indonesia. In the early 17th century, the Dutch eradicated cloves on all islands except Amboina and Ternate to create scarcity and sustain high prices. In the latter half of the 18th century, the French smuggled cloves from the East Indies to Indian Ocean islands and the New World, breaking the Dutch monopoly.
Cloves were among the most precious items in Europe in the 16th and 17th centuries and were worth more than their weight in gold. An illustration of their value can be seen in Magellan’s fateful circumnavigation of the world (1519–1522), which started with five ships and over 250 men. Although only one ship and 18 men returned to Spain, its cargo of about 50 tons of cloves and nutmeg was considered to have made the expedition a financial success.
Today, cloves are still used as a spice in perfumes, mulled wines and liqueurs, aromatherapy, medicinal and dental products, and, stuck in an orange as pomade, an insect repellant.
Clove products can be divided into three: clove buds used whole and ground, are also a raw material for clove bud oil and oleoresin; clove stem oil; and clove leaf oil, used principally as a source of eugenol. Essential oils from the clove tree are divided into bud, leaf, and stem oils. Cloves contain 14 to 20 percent essential oil, the principal component of which is the aromatic oil eugenol (70-90%). Still, odor and flavor differ significantly due to the varying proportions of minor and trace components.
Clove is a small, reddish-brown flower bud of the tropical evergreen tree Syzygium aromaticum of the family Myrtaceae (also Caryophyllus aromaticus, Eugenia caryophyllata, E. aromatica). It is believed to be indigenous to the Moluccas. The clove tree grows to about 8 to 12 meters in height. Its gland-dotted leaves are small, simple, and opposite. The trees are usually propagated from seeds that are planted in shaded areas. Flowering begins about the fifth year; a tree may yield up to 75 pounds (34 kg) of dried buds annually. Just before the flowers open, the rose-peach buds are hand-picked in late summer, again in winter, and then sun-dried, turning a deep red-brown. Cloves vary from about 1/2 to 3/4 inch (13 to 19 mm). Although native to southeast Asia, it is cultivated worldwide, especially in the Molucca Islands, Madagascar, the Philippines, Zanzibar, and Mauritius, as well as in Ternate, Tidore, and a couple of other of the northern Spice Islands in Indonesia. The island of Zanzibar, part of Tanzania, is the world’s largest producer of cloves. Madagascar and Indonesia are smaller producers. The major oil-producing countries are Madagascar and Indonesia.
Cloves are intensely pungent owing to eugenol, extracted by steam distillation to yield clove oil. The leaf oil contains 12% caryophyllene and 90% eugenol as significant components. Unrectified Madagascan oil has a sharp, slightly crude medicinal (eugenol), often phenolic aroma without any of the sweet smoothness of the rectified material. Clove leaf oil is frequently refined and redistilled to remove the constituents that produce the crude odor and discoloration. The process of steam distillation begins when the distiller inserts the chosen plant material, or charge, into a chamber. The plant material is supported on a perforated grid. The water level in the chamber is below the grid, and low pressure, wet steam rises through the plant material. The most important aspect of this method is that the steam is maintained at a relatively low temperature and pressure. As the steam passes through the plant material, it ruptures the plant’s oil-bearing sacs and cavities and liberates its essence, which is carried away into the steam. The steam and essential oil then pass out of the chamber and through a coiled tube surrounded by cold water. Here the steam is cooled, and the condensated water and essential oil flow into a collection vessel. Since the essential oil is insoluble in water, it forms a layer above it, facilitating separation. Small quantities of odorous principles also remain in the water, forming a fragrant water called a hydrolate.
Rublev Colours clove oil is derived from a natural source, redistilled from crude clove oil extracted from the dried leaves of Eugenia caryophyllata, using steam distillation and redistilled for purity.
|Synonyms:||Clove leaf oil, eugenol|
|Chemical Name:||Eugenol (principal ingredient)|
|Appearance:||Clear, pale yellow|
|Odor:||Spicy, phenolic, and sweet|
|Refractive Index:||1.5300–1.5380 @ 20 °C|
|Specific gravity:||1.0460 @ 25 °C|
|Shelf Life:||Four years|
Clove oil is a very potent essential oil and should be used carefully. Clove oil can cause dermatitis and irritate skin and mucus membranes.