Lampblack is a form of carbon. You can think of it as something like very, very finely divided charcoal. Because it is so incredibly fine, a small amount covers a large area giving an intense black color. It forms the basis of the best traditional black inks and has been used to many other ends from shoe polish to blackening gun sights. Lamblack’s extreme opacity and complete resistance to fading are excellent characteristics for use in the arts
Lampblack can be made from burning oily or resinous materials, while collecting the resulting soot. The pitch of pine trees and other conifers make good lamp blacks, as do oils burned with a wick. It has also traditionally been collected from the inside of oil lamp mantles (the clear glass covering over oil lamps), thus the name. The trick to producing it yourself is to burn the material in such a way that combustion is incomplete. When combustion is complete, the carbon is fully burned, but if the flame is interrupted, or just plain inefficient, some of the carbon remains as soot along with other unburned chemicals. The rising black soot can be collected on a metal plate, bowl or flat stone.
Using a large and lumpy, or long, wick will usually create a lot of soot. Another way to create incomplete combustion is to interrupt the flame. You may have noticed that when an object is held in a candle flame, soot results. When the wick is trimmed or made properly and the flame is burning cleanly, the carbon will be completely burned to up at the tip of the flame and no soot results. The truth is that it is somewhat challenging to make wicks which do NOT soot! The modern candle wick is an exception, not the rule. But for making lampblack, you want a whole LOT of soot, so make that flame as dirty as possible.