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GOLD 175
forms appear more granular in character. For this reason
the fibrous forms make the stronger filhngs, although they
have a tendency to draw away from cavity walls while being
manipulated, owing to a certain amount of resilience or spring
in the fibers. The crystalline forms do not possess this
tendency, and are more easily manipulated, but are deceptive
and treacherous preparations for students ' use on account of
their easy working properties.
I. Fibrous Gold.—Fibrous golds are supplied in the form
of foil or sheets 4 inches square, ranging number 2, 3, 4, 5,
6, 8, 10, 20, 30, 40, 60 and 120. The higher numbers are
rolled out by the manufacturer from an ingot, while the lower
numbers are beaten by machinery.
Fibrous gold is classified into (a) Cohesive; (b) Semi-
cohesive; (c) Non-cohesive.
(a) The cohesive foils are, after being rolled or beaten,
annealed by heat and put up in books containing ^i oz.
Before using, the dentist usually re-anneals them, as they will
in time lose much of their cohesive property on exposure to
the atmosphere, accumulating gases, which may be driven off
by heat.
(b) The non-cohesive foils have deposited on their sur-
face certain substances, such as iron, sulphur, or phosphorus,
which destroy their cohesive property.
(c) Some foils are supplied as semi-cohesive, in which
the cohesive property is not developed to its fullest extent.
These are preferred by some operators. The non-cohesive
and semi-cohesive forms are also supplied in ^i oz. books,
the numbers running the same as the cohesive foils.
2. Crystalline Gold.—There are many varieties of this
form made by various manufacturers, all of which are highly
cohesive, and receive different names. Watfs Crystal Gold,
Solila, and Corona are preparations supposed to be both
forms appear more granular in character. For this reason
the fibrous forms make the stronger filhngs, although they
have a tendency to draw away from cavity walls while being
manipulated, owing to a certain amount of resilience or spring
in the fibers. The crystalline forms do not possess this
tendency, and are more easily manipulated, but are deceptive
and treacherous preparations for students ' use on account of
their easy working properties.
I. Fibrous Gold.—Fibrous golds are supplied in the form
of foil or sheets 4 inches square, ranging number 2, 3, 4, 5,
6, 8, 10, 20, 30, 40, 60 and 120. The higher numbers are
rolled out by the manufacturer from an ingot, while the lower
numbers are beaten by machinery.
Fibrous gold is classified into (a) Cohesive; (b) Semi-
cohesive; (c) Non-cohesive.
(a) The cohesive foils are, after being rolled or beaten,
annealed by heat and put up in books containing ^i oz.
Before using, the dentist usually re-anneals them, as they will
in time lose much of their cohesive property on exposure to
the atmosphere, accumulating gases, which may be driven off
by heat.
(b) The non-cohesive foils have deposited on their sur-
face certain substances, such as iron, sulphur, or phosphorus,
which destroy their cohesive property.
(c) Some foils are supplied as semi-cohesive, in which
the cohesive property is not developed to its fullest extent.
These are preferred by some operators. The non-cohesive
and semi-cohesive forms are also supplied in ^i oz. books,
the numbers running the same as the cohesive foils.
2. Crystalline Gold.—There are many varieties of this
form made by various manufacturers, all of which are highly
cohesive, and receive different names. Watfs Crystal Gold,
Solila, and Corona are preparations supposed to be both
