Just thinking

I pulled out the Artists Handbook of materials and techniques. I had a few questions about colors, remembering some conflicting information that I received about using black, particularly Ivory Black. I found some interesting information about it use.
I was told by several teachers while in school not to use it, make your own black, recently it appeared on my supply list for several workshops. hesitant to use it, I did, now after being comfortable with it, knowing its not going to turn into this monster on my pallet I needed to know what its story is.... so here it goes.
Ivory Black (PBk9) Paris Black An inferior grade of ivory black.
" Impure carbon. the black most widely used by artists. Most ivory black on the market is a high grade bone black, made by charring bones. Contains only about 15 to 20 % carbon, and about 60% calcium phosphate, and about 20 % calcium sulfate and other impurities, some of which are water soluble. It should not be used with in fresco or for mortar or cement coloring, as it causes efflorescence. Rather fine, light and fluffy., but somewhat heavier and more compact than lampblack. Very slow drier in oil stand up fairly well, but the use of a purer grade of ivory black is wiser. Has a brownish undertone an compared to the vine black series. Probably dates to the Roman times. True Ivory black carbon is made by burning ivory scraps, has the same properties as bone black, but is finer, more intense , and of higher carbon content. Ivory black is the most widely used artists black and serves well as an all-around black and tinting color. It is the only member of the impure carbon group that is recommended as a permanent artists color. However , it is one of the worst pigments to use full strength as an undercoat in oil painting: a film of any other pigment laid over straight ivory black is extremely likely to crack." pg 66 Artist Handbook.
Do not paint over lamp black or ivory black with  ( zinc white) or other pigments of lower oil content, disaster .

uh...my burnt umber from Gamblin is suffering from overpigmentation....do I throw it out ?
Shit. I have been using it as an under painting thinned with medium.....I wonder what they consider small amounts.

New burnt umber on its way. switching over to Old Holland, they use cold press linseed oil,  better for oil painting, less cracking.