Hi John, Ivory Black is the marketing name for Bone Black now, made from charred animal bones - Ivory Black sounds so much better than Bone Black doesn't it? Genuine Ivory Black used to be made from ivory of course (largely scraps from the carving industry) but thankfully no longer.
Mars Black is an iron oxide pigment; Lamp Black is "nearly pure amorphous carbon", basically soot.
Bone Black is typically a little weaker than other blacks, as well as often having a slightly different colour in tint and undercolour but the differences are often slight, so slight that if you have one black it's often enough since you can always add a dot of this or that to push colour in any given direction. For example, Lamp Black + a touch of umber, and a light hand, would be close enough to many 'Ivory Black' paints to be considered interchangeable.
Blue Black is a commercial mixture: a blend of PB29 and PBk9, French Ultramarine and Bone Black (essentially a darker version of Payne's Grey).
magister militum said:
Ivory black is the "blackest" of all the blacks and also has the best covering power.
Actually the blackest black would typically be Carbon Black or Lamp Black, which are both nearly pure carbon. Bone Black is very slightly lighter in value.
And generally the best covering power will be found with Mars Black because it's opaque, although this is also a property of pigment levels so it varies a bit from brand to brand.
Einion