II4 PAINTING MATERIALS
English Red is a name sometimes used for a light red iron oxide (see Iron
Oxide Red) formerly natural in origin but now, as a rule, made chemically by
heating iron vitriol (ferrous sulphate) with chalk. Artificial English red usually
contains gypsum.
English Vermilion (see Vennilion).
Eosine is the potassium salt of tetrabromofluorescein, CgoHeC^R^K^, and was
first made by Caro in 1871 (Colour Index, p. 194). It was formerly used for pre-
paring red inks of a very fine scarlet hue, but is not a fast color; it fades rapidly
in sunlight. 'Geranium lake* is the name sometimes given to a brilliant bluish-red
lake made by precipitating eosine on an aluminum hydrate base.
Extender is an inert (see also Inert), colorless or white, and usually trans-
parent body used to diffuse or to dilute colored pigments. Extenders up to certain
proportions may increase and improve the wearing qualities of paints. The
barium sulphate which is used up to 75 per cent with titanium dioxide may be
regarded as an extender. The cost of the mixture is materially less than that of
pure titanium dioxide, but there is not a proportionate lessening in hiding and
covering power. The same is true of the calcium sulphate which is often present
in considerable quantities in artificial iron oxide reds. Some of the insoluble dye
pigments or toners have such high tinctorial power that it is more economical
and practical to use them with carriers and extenders. When an extender is added
to a paint or pigment in such quantity that it lowers the tinting strength, it
becomes an adulterant.
Filler is a white, inert, transparent material, low in refractive index, which is
used in paste form to fill imperfections in a surface that is being prepared for
finishing. Wood filler is a paste made with crystalline silica (silex). It is used to
fill the pores or grain of the wood with hard, non-shrinking, transparent material
so that varnish coats will go on smoothly and take a fine polish. The word,
'filler,' is sometimes used synonymously with 'extender' (see Extender).
Hake White (see White Lead).
Flavine Lake (see Quercitron Lake).
French Ultramarine (see Ultramarine Blue, artificial).
Fuchsia (see Magenta).
Fuller's Earth is a hydrous aluminum silicate of variable composition belong-
ing to the clay group of minerals (see Ladoo, pp. 231-240). It occurs in sedi-
mentary deposits in many parts of the world but particularly in Florida and in
England. It is white, buff, gray, or olive in tint, and has physical properties about
the same as clay, except that it is characterized by a marked ability to absorb
basic colors from animal and vegetable oils. It gets its name from its original use
which was for fulling or removing grease from cloth.
Gamboge is a yellow gum resin which for centuries has been used as a pig-
ment in die Par East. It is produced by several species of trees of the genus
Garcinia, indigenous chiefly to India, Ceylon, and Siam. It came to Europe quite