Copal is among the hard resins, others of which are amber, mastic, and sandarac. They are hard, relatively brittle, odorless, and tasteless and exhibit a glasslike surface. Long known as an excellent product for exterior decoration, the hard copal from Congo is considered the most desirable of all copals for painting. Strokes stay where they are placed and dry to a diamond hard sheen. Due to political strife, true Congo copal has been all but nonexistent on the markets.We have been able to import a quantity of pure Tanzanian copal, which is considered the ultimate Congo copal. The rarest of all the copals is that which comes from Belize. It has the shine and excellent handling characteristics of true Congo copal but is somewhat softer. It's a bit more flexible because, rather than being shipped dried, this arrives as a raw resin with many of the essential oils intact. Harder than Belize is Manilla copal, one of the fossile copals. Harder than Manilla is Congo, with the hardest of all being Amber medium. All have their unique handling qualities and can be used in the same painting. Unfortunately, the supplies of this excellent copal are sporadic because it is gathered by men who live high in the Maya mountains and is packed down to Punta Gorda along with medicinal roots and herbs they collect. No one can predict when a shipment will arrive and how much will be available. It is wrapped in palm leaves and requires melting and filtering before it can be used to make copal painting medium. Every painter should have a variety of copal painting mediums as part of their basic kit. The effects of copal on flake white Flake white reacts with copal unlike most other paints. A small amount of copal makes the paint become stiffer because of the formation of lead soaps. This makes it great for heavy impasto. More copal can be added to make the white more fluid and easier to brush. Futher addition of copal makes it stringy and threadlike. The colors dry lustrous and retain their brilliance. The paint is incredibly durable. A painting will dry faster when copal is used.