34 BultLDING AND EKourpMENT 
of gravel. The sand should be sharp building sand and the gravel 
should be washed pebbles, ranging in size from one-half to one 
inch. ‘The top dressing should be not less than one inch thick, 
consisting of one part of eement and one and one-half parts of 
sharp building sand. It should be carried up on the walls and 
partitions at least two inches, forming a sanitary cove. After 
finishing, the floors sheuld be allowed to harden for at least 
two weeks. ‘This will greatly prolong their life. It is advisable 
to use cement hardener such as Master Builders’ cement, or 
Lapidolith, ete., which will help to make these floors more nearly 
wear-, water-, dust- and crack-proof. It is difficult to keep the 
condensery in sanitary condition and to protect the product 
against contamination, unless the floors of the factory are and 
stay free from cracks and holes. 
Ventilation—.\ proper and effective system of ventilation 
is another very important and too often entirely neglected factor 
in the planning of the condensed milk factory. This applies ta 
all parts of the plant where work is being done, but it is espe- 
cially essential in rooms where [ree steam escapes. ‘The ventilat- 
ing system should be adequate to afford ready and quick escape 
of steam, to remove foul air and to facilitate the regulation of 
temperature. Unless free steam does promptly find an exit from 
the factory rooms, it condenses on the walls and ceilings, mak- 
ing them sweat profusely, causing corrosion of the walls and 
ceiling, deterioration of motors and other similar equipment, 
and molding of supplies; this is especially the case during the 
winter months. ‘lhe removal of foul air and the control of the 
temperature of the air are essential for the comfort, health and 
efficiency of the employes. 
‘Phe system of ventilation that will accomplish efficient ven- 
tilation will of necessity vary with the type of plant and arrange- 
ment of equipment. Gravity ventilation is, under average con- 
ditions, inadequate to produce satisfactory results in factories, 
like milk condenseries, where there is bound to be much escape 
of free steam. ‘he exchange of air is not rapid enough to remove 
the steam before it condenses on the walls and ceilings, espe- 
cially in cold weather It is, therefore, advisable to provide for 
some form of forced ventilation. Under certain conditions of 
construction an air flue connecting with the smoke stack may 
