Cork insulation; a complete illustrated textbook on cork insulation ...

480 CORK INSULATION
because it will be washed off. It must be given time to set. With
sunshine it will dry in two to three hours. A man will soon learn i..
give 350 to 400 square feet surface per hour one coat. The quantity
of the various materials required per 100 square feet of surface may
be obtained from the manufacturers. The following data were obtained
from the Lewis Asphalt Engineering Corp.:
Karnak Korkphalt 70 lb. per layer of corkboard
Korkseal (or Krodeproof), first coat 4 gal.
Korkseal Mortar (finish coat) 5 gal.
Korkseal Enamel, white, per coat Ys gal.
Korkseal Aluminum, per coat % gal.
Strength.—Tests have been made for the United <strong>Cork</strong> Companies,
New York, to determine the tenacity of adhesion of a 3-in. thick
slab of corkboard cemented to concrete. When a pull was exerted
of 1,360 pounds per square foot cork, the cork yielded, but not the
asphalt emulsion, which proves conclusively that the emulsified
asphalt furnishes a very reliable bond. In fact, the adhesive strength
of Par-Lock asphalt alone was found by the Investigating Committee
of Architects and Engineers, New York, to exceed 125 pounds
per square inch, equivalent to 18,000 pounds per square foot. Its
ductility is rated at four to five centimeters at 77° F. The penetra-
tion of a needle bearing a 200 gram weight is twenty-five to thirty
millimeters per minute at 77° F. The re-melting point of these surfac-
ing asphalts is between 200° and 215° F. when tested by Bureau of
Standards ring and ball method. The re-melting point of the hot
asphalt used for dipping one face and two edges of corkboard should
be between 180° and 200° F. It should be heated to the consistency
of molasses, the slabs firmly pressed against the surface asphalt,
such as Krodeproof, until the asphalt in the joints chills.
Mastic Asphalt Facing.—The Korkseal or asphalt mastic fin-
ish, J/^-in. thick, above described, is an improvement over the
method of ironing on the asphalt plaster at the factory to
each slab of cork, because the subsequent patching up of the
many lineal feet of joint is a difficult and expensive task,
and the result is not equal in air and water tightness to that of a
continuous troweled facing. Not to chip off readily, a tough grade
of asphalt is used which is hard on the saw when fitting slabs into
place. This asphalt becomes very brittle at low temperature. It has
to be a hard variety so as not to run during shipping in summer.
Some <strong>insulation</strong> manufacturers do not urge the use of the Korkseal
asphalt plaster where the cork is exposed to injury from the handling
of goods. There they recommend again the old Portland cement
plaster finish, at least J^-in. thick; but even here the advantage of
moisture proofing should not be sacrificed. One can erect suitable
fenders, rails and baseboards to prevent truck wheels from damaging