CONVICT LABOK FOR EOAD WORK. 141 
PERMANENT FRAME STRUCTURES. 
Structures of this type, similar to that shown in Plate X, figure 2, 
are used in the concentration or central camps of a few of the south- 
ern counties. In design, they are similar to frame structures used 
for other purposes, and hence they will be given no special treatment 
in this bulletin. 
MISCELLANEOUS DATA ON BUILDING MATERIALS. 
Paint. 
The solid ingredient of paint is called the pigment; and the liquid 
part, the vehicle. White lead and white zinc are the common white 
pigments, and the vehicle usually is linseed oil, with sometimes the 
addition of a little turpentine or other volatile solvent. 
DRIERS. 
These are compounds of lead and manganese dissolved in oil, and 
this solution thinned with turpentine or benzine. They act as car- 
riers of oxygen from the air to the oil, and their addition to a paint 
makes it dry more rapidly. Not more than 10 per cent by volume 
of a drier should be added to oil. 
PRIMING COAT. 
This is the first coat applied to the clean surface. The priming coat 
for wood usually is made by thinning a gallon of ordinary paint with 
a gallon of raw linseed oil. In all woodwork, nail holes and other 
defects should be filled with putty after the priming coat has been 
applied; but if the wood be resinous, knots and resinous places 
should be covered with shellac before the priming coat is put on. 
Pitchy woods, such as southern yellow pine and cypress, do not 
absorb oil readily, and turpentine should be substituted for part of 
the oil. 
SECOND AND THIRD COATS. 
The priming coat, having been absorbed largely by the wood, a 
second, and possibly a third, coat of paint should be applied. The 
most common paint used on houses is white lead. This is commonly 
sold as paste white lead containing 8 per cent of oil, 100 pounds 
being equal to 2.8 gallons in volume, and it is commonly mixed with 
3 1 gallons of raw linseed oil, 1 quart of turpentine, and 1 pint of 
drier to make 6f gallons of paint for the second coat, or with 4 gal- 
lons of oil, 1 pint of turpentine, and 1 pint of drier for the third coat. 
If a vehicle composed of half linseed oil and half turpentine be used 
in the paint for the second coat, it will have the effect of making the 
paint dry with a dull or "flat" surface instead of a glossy surface, 
and the third coat will adhere better. If white zinc is used, 9i 
pounds of dry zinc oxide and 0.57 gallon of oil make 1 gallon of paint; 
