After three days of drying the canvas may be folded up
without sticking together, and is, of course, waterproof. Canvas
waterproofed in this manner makes an excellent covering for
portable canoes and canvas boats. The color mixture for the soap
and second application is made from 1 lb. of lampblack and 6 lb.
of yellow ocher, both in oil; the finish coat may be any color
desired. When no paint is to be used on the canvas it may be
waterproofed with a mixture made from soft soap dissolved in hot
water, and a solution of iron sulphate added. Iron sulphate, or
ferrous sulphate, is the green vitriol. The vitriol combines with
the potash of the soap, and the iron oxide is precipitated with
the fatty acid as insoluble iron soap. This precipitate is then
washed, dried and mixed with linseed oil.
** Building a House in a Tree Top [146]
The accompanying photograph shows a small house built in a tree
top 20 ft. from the ground. The house is
[Illustration: Lofty Sentry Box for Guarding Watermelon Patch]
5 ft. wide, 5 ft. 1 in. long, and 6 ft. 6 in. high. A small
platform, 2 ft. wide, is built on the front.
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