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Exterior and interior paints - Oil
paint differs from varnish in that it dries by oxidation and increases in bulk, whereas a
varnish dries by evaporation and diminishes in bulk. Paint consists of two parts, the
vehicle and the pigment. Linseed oil was the usual vehicle in those days; in drying it
oxidized and formed a tough, leathery skin termed “lenoxin.” If used alone it
was too thin and porous; to give it the necessary body or substance, a pigment was added -
usually a mineral oxide. Although it then formed a tough elastic covering, it was neither
perfectly air- nor watertight, for it contained minute pores which enlarged as the paint
aged. To provide the durable and watertight surface required, two or more coats were
applied so that each could fill or cover the pores or fissures in the one below.
To achieve the desired color in a given paint, there were several pigments in
general use in shipyards of the time and into the years which followed: red lead or oxide
of lead, white lead or carbonate of lead . . . (continued) |
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Image above, Newalls Insulation Co. Advertisement. The Shipbuilder / Author’s collection |
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Antifouling
paint - The biofouling of iron and steel ship hulls was, and still is, a constant
source of trouble for ship owners. As marine growth accumulates over the large underwater
hull area, a ship's speed becomes markedly reduced, with a corresponding rise in the
consumption of fuel. In ships such as Titanic, this meant a large additional
expenditure of coal. As speed was the name of the game in 1912, fouled hulls became a
serious chore to attend to. Ever since the introduction of iron ships there has been a
sustained endeavor to produce a perfect antifouling paint - a composition which would be
completely resistant to the attachment of seaweed and barnacles. Hundreds of methods of
avoiding fouling had been tried, patented or proposed by 1912 (even before 1870, 200
patents were taken out), but a perfect one had not yet been invented, nor has there been
one to this day . .
. (continued) |
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Cement -
Portland cement was composed of chalk and clay (lime, silica and aluminum). When mixed, or
“gauged,” with water into a dough, it quickly underwent a chemical and molecular
change, stiffened and set. Some cement would set in ten minutes or less from the moment of
mixing with water, while others took much longer - half an hour or more. The set did not
leave the cement hard, it merely transformed it from a soft, wet dough into a
comparatively dry solid; its surface, formerly glossy with water, became dry, and, to work
it further, more water was added. The final set, or actual hardening of the cement,
occurred gradually after the first set. A distinctive characteristic of Portland cement is
that it hardened just as well under water, and for this reason was termed “hydraulic
cement.”
Portland cement was extensively used in the shipyard. As a wash, it formed a
substitute for paint; and as a thick layer or paving, it protected the bottom plating from
attrition as well as from corrosion . . . (continued) |
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Other topics in this chapter:
Anticorrosive coverings - Shell markings (draft markings, sheer stripe, name and
port, freeboard markings, draft markings) |
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