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- Browns And The Cold Semi-neutral Grays Marrone Is Practically To
- Also Called Scarlet Chrome Is A Bright Chromate Of Lead Of An
- Black Chalk
- Composition Chemical Analysis Has Shown Several Of The Blues To Be
- Burnt Verdigris
- Belong The Dutch And Flemish Schools; The Sensible Which Aims At
- Less Known As English Red Prussian Red And Scarlet Ochre True
- Olive In Dark Green; Russet And Citrine In Dark Orange The
- Known Likewise As Raw Sienna Earth Terra Di Sienna &c Is A
- Root Of The Anchusa Tinctoria Commonly Known As Alkanet A Plant

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- Distilled Verdigris Or More Properly Refined Verdigris The Best Is
- Sometimes Called China Or Chinese Ink Is Chiefly Brought From
- Egypt The Greeks Obtained The Knowledge Of Their Ars Chromatica
- While We Avoid The Compounding Of Contrasting Colours That Is The
- Only That Of Extreme Light Objects Opaque It Follows That White Is To
- Secondary Colours Are Three Only Orange Green And Purple
- Have To Be Learnt For Each Pigment Has Its Own Peculiar Habitudes
- These Are False Appellations Of A White Lead Called Also French
- Of These There Are Three Tints Deep A So-called Pale And Lemon
- Sometimes Designated Drop Gum And Variously Written Gamboge

Liquid Indian Ink Is A Solution For Architects Surveyors &c

TTITLE IVORY BLACK

is ivory charred to blackness by strong heat in closed vessels.
Differing chiefly through want of care or skill in preparing, when well
made it is the richest and most transparent of all the blacks, a fine
neutral colour perfectly durable and eligible both in water and oil.
When insufficiently burnt, however, it is brown, and dries badly; or if
too much burnt, it becomes cineritious, opaque, and faint in hue. With a
slight tendency to brown in its pale washes, this full, silky black is
serviceable where the sooty density of lamp black would be out of place.
It is occasionally adulterated with bone black, a cheaper and inferior
product.

Being nothing more nor less than animal charcoal, ivory or bone black
had best not be compounded with organic pigments, in water at least. It
is well known that this charcoal possesses the singular property of
completely absorbing the colour of almost any vegetal or animal
solution, and of rendering quite limpid and colourless the water charged
with it. If a solution of indigo in concentrated sulphuric acid be
diluted with water, and animal charcoal added in sufficient quantity,
the solution will soon be deprived of colour. The more perfect the ivory
or bone black, the more powerful is its action likely to be: either over
or under calcined, animal charcoal is less energetic; in the former
case, because it is less porous; in the latter, because the animal
matter, not being wholly consumed, makes a kind of varnish in the
charcoal which interferes with its acting. To a greater or less extent,
gums, oils, and varnishes serve similarly as preventives, thereby
decreasing the danger of employing these blacks in admixture; but, in
the compounding of colours, nothing is gained by needless risk. To mix
with organic pigments, therefore, blue or lamp blacks should be
substituted for those of ivory or bone; that is, vegetal charcoal should
be used instead of animal. It is a question whether even with inorganic
pigments the adoption of the former in admixture would not be advisable.
It was once the general opinion that the action of animal charcoal was
limited to bodies of organic origin, but it has since been found that
inorganic matters are likewise influenced. "Through its agency," says
Graham, "even the iodine is separated from iodide of potassium;" whence
probably pigments containing iodine would suffer by contact. The
investigation of Weppen appears to prove that the action of the charcoal
extends to all metallic salts; with the following, no doubt remains of
this being so, to wit:--the sulphates of copper, zinc, chromium, and
protoxide of iron; the nitrates of lead, nickel, silver, cobalt,
suboxide and oxide of mercury; the protochlorides of tin and mercury;
the acetates of lead and sesquioxide of iron; and the tartrate of
antimony. Whether animal charcoal exercises any deleterious influence on
pigments consisting of these metals, and, if so, how far and under what
circumstances, can only be answered when our knowledge of the properties
of pigments is greater than it now is. At present, perhaps, it is safer
to choose vegetal charcoal for mixed tints, inasmuch as, although it
shares the property of bleaching in a certain degree, it does not
possess the same energy.

TTITLE LAMP BLACK,





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