What is the difference between a ‘dry oil’ and a ‘drying oil’?
Terminology can be confusing, especially when talking about these two different types of oils
The words sound so similar, and are, but in trying to convey the qualities behind them they are radically different.
Drying oils are quite literally the oils that dry.
Oils high in mono and polyunsaturated fatty acids will dry and harden to the touch over time when exposed to oxygen, heat and light.
An Example from the Art World
Linseed oil used in art and oil painting is essentially flax seed oil. And being high in polyunsaturated fatty acids, flax seed oil will dry and harden over time.
These drying oils are used to make paint, inks and varnishes. They dry to the touch. Think Rubens or Leonardo da Vinci, linseed oil was common as a medium for paint pigments during the Renaissance period. Even linoleum flooring is also made from linseed oil as well as fillers and pigments.
So then what is a dry oil?
Dry in this context has to do with the feel of the oil, it feels dry when applied to the skin, not oily or greasy.
Tannins in Oils
The dry oils have tannins in them, which are astringent, polyphenolic molecules that bind to and precipitate proteins and various other organic compounds and are found in a wide range of plant tissues including lipid oils.
Tannins come from tannum the word for oak bark one of the major sources of tannins used for tanning animal hides to make leather. Oak bark and galls, are used as astringent compounds by herbalists to tighten and pull together tissues for healing wounds.
When trying to differentiate between drying oils, literally dry to the touch, and dry oils think of puckering. Astringency is puckering think of very strong black tea, or persimmons, or quince, or cranberries.
Tannins and Tea
We lived in England for a time about 20 years ago and I still remember how black tea was served in an English tea shop. A very very strong brew would be brought to the table along with a second pot of hot water to dilute the tea to your liking. But that first pot was strong enough to curl the enamel on your teeth.
This is the nature of tannins. And, so I always first think of camellia seed oil when talking about the dry oils because camellia oil is pressed from the seeds of the Camellia plant the source of black and green tea. Camellia sinensis, the tea plant, or C. japonica or C. Oleifera, all have lipid compounds that can be used for skincare.
Drying oil – is an action the oil dries to the touch
Dry oil – it feels dry on the skin and is associated with puckering, tightening like very strong tea
How to Use
The dry oils are good for skin with over active sebaceous glands, oily skin and skin that breaks out easily.
High tannin oils like camellia, hazelnut, grapeseed will help to calm overly oily skin.
The drying oils have important skin benefits, but you want to protect them from drying or going rancid.
These are the polyunsaturated dominant fatty acid oils like walnut, chia seed, flax and others that absorb deeply into the skin.
These oils are sensitive to oxygen, which will trigger the drying process and so should be kept cold and dark in storage and used quickly.
Have you experienced the difference between dry and drying oils in your work? Leave a comment below.