Thursday, February 17, 2011

A nerdly drawing, complex fluids, and ...paint?

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This is my latest drawing, inspired by more diagrams and hours spent peering through a microscope than I'd care to count.

One of the areas of science that has always fascinated me is complex fluids. These are liquids which have structures inside them, but the structures and order are so soft and fragile that the tiniest bit of force (actually stress) is enough to break them apart.  Complex fluids will behave like liquids when they're flowing, but if they rest for a while, the fragile structures reform.  

Wednesday, February 16, 2011

Siccative oils

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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?

Linoleic Acid:  A Polyunsaturated fatty acid with 2 unsaturations.  This is a molecule commonly found in drying oils, also called siccative oils.