Saturday, August 17, 2013

Sunflower Pollen as Paint Pigment

Sunflower Pollen - Pigment/Paint

Our house is still ramping up its dye-making capabilities.   The garden continues to grow enough that we can now harvest the Madder roots without depleting the patch (started in 2011 –link to post).  The basement will soon be a functional workshop, with plenty of lighting, a sink, electricity, and benches.   
 sun flowers for dyeing
Thanks to my wife’s gardening, we have plenty of sunflowers.  Some are of the Hopi variety, the seeds of which have been used by Native American Indians to prepare purplish/gray dyes.  Whereas I hope to make my own paints, she plans to dye fabric (DesignLab link) expect a post later on the seed-dye making.  Many flowers are brought into the house and drop pollen.

Given the nature of pollen to be colorful, tiny, and sticky, I started collecting it to use as pigment. First we had to replace the fabric tablecloth beneath the vase that was being “painted”; aluminum foil worked well since the pollen did not adhere to it, and it could be folded into a funnel  to deliver the pollen into a jar. 
sun flower pollen hopi

Sun Flower Pollen - Microstructure

To learn about how it may work as a pigment, let’s have a look at the pollen grains: (1) dry,  (2) in oil, and (3) in water.  Below, the pollen-in-air color image is a brightfield microscopy image; to show the detail, differential interference contrast microscopy (monochrome image) was performed. Most were a-spherical (“not spheres”) and ~10microns in width (that’s ~1/10 the length of a human hair). Clearly their spikes help them to stick to substrates.  The grains are a mixture from several sunflower plants.  Most were yellow, but some were purple.
Dry Sunflower Pollen

To make paint, pigments are dispersed into liquids.  These host liquids are usually water-like or oil-like.  Actually, microscopists often embed dry samples into liquids, to reduce scattering and improve imaging (this works if the samples do not react or transform in the liquid). These immersion tests reveal how these grains may be color-fast (or not). 
 sunflower pollen in oil
Turns out, the sunflowers lost their color in the oil; but their shell shapes did not change.  This means that the pollen is filled with a hydrophobic liquid (dye), and that the shells are porous.  Actually, the spherical grains seemed to leak less (I will have to investigate further if only certain sunflowers produce those). In water, the yellow dye was slowly replaced.  It was shot out of the shell as drops.  This confirms that the dye is hydrophobic, and that the shells are porous. 

This work will inform a paint recipe.  The observations are somewhat aggravating since they indicate it may be difficult to keep dye inside the grains whether a water-paint or oil-paint is made.  For now, I will keep collecting the pigment and will lean toward design an aqueous host phase.