Mad About Science: Acrylic paints

By Brenden Bobby
Reader Columnist

By the time you are reading this, I will be somewhere warm and sunny, holding aloft last week’s issue of the Reader in front of a cactus. I’m several years overdue for a vacation and it’s time to hit the open road and see the Grand Canyon from ground level. Fear not, dear readers, for this article that you use to clean up spills continues on, as I am a prepared and deadline-conscious adult, writing to you from an undisclosed location in the recent past.

Have you ever wondered how paint works? Likely one of humankind’s very first inventions, paint seems like such a simple concept. You have colorful sticky liquid that you can smear across a surface using your hands, a brush, or even a can and voila. You have created art.

The science behind paints — and acrylic paints in particular — is a little bit more involved than that.

It all begins with pigment. Pigments start in many different forms, whether they’re minerals, insect shells or something synthetic that humans created in a lab. Pigments absorb and reflect very specific wavelengths of light to produce color. When humans crush pigments into a fine powder, they become easier to apply to other things. However, unbound pigments will produce an uneven powdery coat on the surface to which they are applied without sticking there for a long time.

The key to keeping pigment where you want it lies in the acrylate polymer, which acts as a binding agent that locks the pigment in place. Acrylic polymers, often referred to as “acrylics,” are synthetic polymer chains that will appear as a hard transparent substance when present in large quantities. Those big see-through sheets dividing cashiers, bank tellers and librarians from their customers and patrons throughout the pandemic are sheets of acrylic. When painting, you need one more item present in order to make your pigment-tinged acrylic malleable and easy to spread.

Water acts as the vehicle for acrylic paints to be easily transferred to other surfaces. Water, carrying the acrylic polymer and the pigment, transfers to the bristles of your paintbrush, which is then partially transferred to whatever it is that you’re painting. Applying paint to a paper canvas works especially well, as the paper will soak up the water and hasten its evaporation. 

Once the water evaporates, a chemical reaction occurs in which the acrylic has formed a protective barrier around the pigments and bonded to the surface on which they’ve been placed. Since this effect is too small to see in detail, our eyes just process pretty colors painted onto a surface.

Acrylic paints can be applied to a range of surfaces, not just paper. Due to the relatively simple chemical process of acrylic paints, you can perform some really unique things with them when you apply other mixtures to the paint. 

Solvents like paint thinners and isopropyl alcohol should always be used with care. Their fumes are toxic and they are extremely flammable. So long as you are very careful with these substances, you can create really unique effects by thinning your paint and performing a direct pour. Alcohol evaporates very quickly, and with a lower density than water, likes to rush toward the surface rather than sink into a medium. As the alcohol races to the surface, it carries the paint with it to create wild fractal patterns and weird blending effects that you have to see to believe.

Due to the thinning nature of isopropyl alcohol as a solvent, it is often mixed in certain concentrations to thin acrylic paint for use in an airbrush. An airbrush is a simple, but highly effective tool to enhance your painting experience. It’s essentially a metal pen attached to an air compressor with a tiny pot of paint on top. Using a trigger, you open the core of the pen to pressurized air to blow through the airbrush, carrying a mist of paint, alcohol and air in a targeted direction. This is best used to create thin, smooth coats of paint with soft edges, and is the same process as using a rattle can, but considerably safer and easier to control.

You’ve probably sussed out by now that my preferred painting medium is miniatures. Minis come in a variety of materials, from plastic like PLA or ABS, to metals like bronze and aluminum. I print my own from a photopolymer resin using my 3-D printer. Painting minis is an exciting and meditative experience all at once. Your brain is so focused on what you’re doing that it shuts out anything else that may be bothering you, yet offers little rushes of dopamine with each pass of your brush.

Do you like to paint minis? I’ll be hosting a relaxed instructional gathering on Tuesday, March 29 from 3-5 p.m. at the Teen Lounge at the Sandpoint Library (think: Bob Ross-style, as we’ll talk and paint together). This will be geared primarily toward teens and young adults, but anyone interested in picking up the hobby is welcome to join. 

We’re calling this a BYOM event, for “bring your own mini.” If you have a box of gray shame, or are picking up a brush for the first time, then this event is for you. We’ll have some hobby paints on hand, but definitely encourage you to bring your own supplies if you have them.

See you on the other side of the vacation, and stay curious, 7B.