Known Likewise As Raw Sienna Earth Terra Di Sienna &c Is A





ferruginous native pigment, firm in substance, of a glossy fracture, and

very absorbent. It is of rather an impure yellow colour, and much used

in landscape, being very serviceable both in distance and foreground.

Unless proper skill is exercised in its preparation, the sienna has the

objection of being somewhat pasty in working. Being little liable to

change by the action of either light, time, or impure air, it may safely

be employed according to its powers, in oil, water, and other modes of

practice. It possesses more body and transparency than the ochres; and

by burning becomes deeper, orange-russet, as well as more transparent

and drying.



Raw sienna compounded with cobalt, indigo, or Prussian blue, and a very

little bistre, yields good sea greens, that with indigo being the most

fugitive. Alone, it is adapted for shipping, sails, baskets, decayed

leaves, brooks and running streams.



TTITLE STRONTIAN YELLOW,



To justify its name, should be a chromate of strontia, a compound very

slightly soluble in water, and not more stable than the zinc chromate.

The pigment, however, now sold as strontian yellow is usually formed by

admixture, and contains no strontia whatever. Its absence cannot be

considered a disadvantage, for the substitute possesses a durability to

which the original could lay no claim. Other things being equal, we

prefer an original pigment to one compounded, but a good mixture is

decidedly better than a bad original. A light primrose, clear and

delicate.



* * * * *



The foregoing comprise those yellows more generally employed, advisedly

or not, as the case may be. The following are for the most part not

commercially obtainable, a remark that will apply in ensuing chapters to

all numbered colours printed in italics. As a rule, these have become

obsolete as pigments, or have never been introduced as such. The former

could not well be omitted in a work of this kind, and the latter deserve

notice as being at least suggestive. At present, many of them must be

regarded as mere curiosities, being obtainable only from materials of

excessive rarity. In time, however, the sources whence they are derived

may possibly be found in greater abundance, and these now fancy products

prove of value to the palette. The new metal indium, for instance,

furnishes a bright yellow sulphide, like that of cadmium. The colour

could not be affected by foul air, and might possess other advantages

which would render indium yellow a desirable pigment. With regard to

those compounds available for artistic use, but which have not to our

knowledge been adopted, several are quite ineligible. It may be thought

that they are needlessly referred to, but they are mentioned as a

warning and a guide. Strange preparations have been offered as pigments,

and sometimes accepted, witness turbith mineral, iodine yellow, &c. In

these days of chemistry there is less chance for them, but they are

continually submitted to one's notice, their merits being enlarged upon

in proportion to their worthlessness. Through an exceptional ignorance

they may still gain a place, and it has been deemed, therefore, not

superfluous to allude to them. At the same time we do not pretend to

exhaust the list, any more than we claim to note all substances

possessing colour, but yet not admissible as pigments. Some there are

which do not retain that colour on drying; others, whose preparation

involves processes too nice, complicated, or expensive, for

manufacturing purposes. There are many colours, again, which exist only

on paper. We have too often found the imaginations of chemical writers

far more vivid than the colours they describe. Gorgeous yellows turn

out dingy drabs; dazzling scarlets dirty reds; and brilliant blues dusky

slates. As respects colours, most books of science need revising.





Known Likewise As Kremnitz Crems Or Krems White Is A Carbonate Krems In Austria It Is Also Called Vienna White Being Brought From facebooktwittergoogle_plusredditpinterestlinkedinmail

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