Calcium Carbonate
Calcium carbonate, also known as marble dust, is available in
many different forms. The cheapest is athletic field marker,
which is sold in 50 pound bags, but the color and grain may
vary as there is little quality control in the product (color isn’t
important when you’re sliding into third base). It’s widely
available and very cheap (Figure 2.15).
The best source that’s higher in quality as an additive is
Fredrix Powdered Marble Dust. Near neutral in pH, it’s very
consistent in color and grain, and is what I recommend
using. It’s available from most art supply outlets.
Hardwood Powder
This is also known as sawdust. It’s often available for free
from any fine wood shop. You can use it in place of or with
the calcium carbonate to make a dark- chocolate colored
fresco—just make sure you remove any chunks. Also, be care-
ful to use only clean raw wood and not finished wood—the varnish comes at the
end of the process, not the beginning (see Fruit Basket in Chapter 16). I get my sup-
ply from the vacuum bag the wood worker has on the sanding bench.
Iridescent Powders
Sparkling additives can add interest to an image and increase the apparent lumi-
nosity of the art. One of these is a quartz additive from McCloskey that reflects light
beautifully. The glint of light it creates is similar to polished granite. Since it does
not dissolve in any liquid, use a coarse strainer with this product as it might have
problems going through fine strainers.
The other products I use a lot are powdered iridescent colors from fine art supply
stores. They are made from mica, and reflect light and different colors. You can
also purchase them already mixed into many brands of acrylic paint. Check the
book’s website for additional product information, www.digitalalchemybook.com.