GLAZING AND PAINTING 99 



The price of single-thick is from 60 to 70 

 per cent, of the cost of double-thick. Amer- 

 ican window-glass is the best that can be 

 procured. The price varies greatly from year 

 to year, probably more than does the price 

 of any other standard building material. 



American-made glass is packed in boxes of 

 about 50 square feet each. Foreign glass 

 comes in boxes of approximately 100 square 

 feet each. The number of lights per box of 

 the various sizes of American-made glass is 

 shown in the following table: 



LIGHTS PER BOX ACCORDING TO SIZE 



Lights Lights 



Size per box Size per box 



7x 9 114 14x16 32 



8x10 . 90 14x18 29 



8x12 75 16x20 23 



10x12 60 16x24 19 



10x14 51 18x18 22 



12x12 50 18x20 20 



20x14 43 18x24 17 



12x16 38 20x20 18 



14x14 37 20x24 15 



Plate glass is seldom used in commercial 

 greenhouses, as its cost is prohibitive. It is 

 but little better than A grade window-glass 

 for this purpose. In conservatories where 

 strength is more important than transpar- 

 ency, fluted or corrugated glass, or glass in- 



