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OF ENGINEERING FORMULÆ.
Dabk Deying Oil (fob Paint).
1 gallon linseed oil.
2 lb. of red-lead.
3 lb. of umber.
4 lb. of litharge.
The linseed oil is heated to about 200* Fahr, and the scum
removed. The red-lead, umber, and litharge are then added,
and the -whole raised to 400° Fahr., and kept at that heat
about 3 hours. It is then allowed to settle before decanting
off.
Raw Drying Oil.
Add white-lead in the proportion of 1 lb. of lead to 1 gallon
of linseed oil; then allow it to settle for a week. .
. Copal Varnish.
Fuse 8 lbs. of African gum copal; add 2 gallons of clari-
fied oil. Boil very slowly for 4 or 5 hours until (jiute stringy,
and mix with 3; gallons of turpentine.
White Hard Spikit Varnish.
Dissolve 3i lbs. gum sandarach in 1 gallon of spirits of
wine; when dissolved add 1 pint of turpentine. For brown
varnish substitute shellac for sandarach.
Black Vabnish. ■
Fuse -3 lbs. of Egyptian asphaltum, and when liquid add
i lb. of shellac and 1 gallon of turpentine.
Turpentine Varnish.
i Ib^of resin dissolved in a pint of oil of turpentine warm.
Crystal Varnish fob Tkacing Paper.
Canada balsam dissolved in oil of turpentine in equal
quantities.
Driers.
Litharge or oxide of lead; red-lead and sulphate of zinc are
also used. Oxide of manganese is used fur quick drying.
- From J- to 1 lb. of driers are used to a gallon of oil. Resin is
sometimes juixtd -with paint to make it dry.
Painting Old Work.
Old paint should be washed with soap and water or a solu-
tion of pearlash, and afterwards rubbed with pumice-stone.
To remove old paint, dissolve 1 ounce of soft soap and 2
ounces potash in boiling water, and add 4 ounces of quick-
lime. Apply hot, and leave it on for 12 or 15 hours.