1. Introduction -drying oils and oil films
Siccative oils are the drying oils used in artists' oil based paints. If you paint with oils, you may have noticed that there are a large number of oils available. Some oils are from different plant sources, while others may have been treated or extracted in different processes. If you start looking through the available information on oils for oil painting, you'll find that different oils have different properties that are important to painters. Two key properties, often discussed, are
yellowing and
drying time. However there is also a third important property to consider - oil film
hardness (and
toughness).
Yellowing in oils is complex, and involves a good bit of Chemistry - we'll tackle yellowing in a later post with more background information covered.
Drying and film hardness are correlated to the amount and types of
polyunsaturated fatty acids in the drying oil. So the next logical questions are :
What are
polyunsaturated fatty acids?
What is their role in oil film formation?
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Linoleic Acid: A Polyunsaturated fatty acid with 2 unsaturations. This is a molecule commonly found in drying oils, also called siccative oils. |