104 



GREENHOUSES 



Fig. 58. Putty knife 



for glazing roofs as is 

 lapped glazing. More than 

 90 per cent, of the growers 

 interviewed on this subject 

 preferred lapped glass 

 roofs. On side and end 

 walls, glass is quite com- 

 monly butted with good 

 results. 



Putty. Putty is a pli- 

 able substance used in set- 

 ting glass. The principal 

 ingredients are whiting 



and linseed oil, and its chief virtues are that 



it is easily worked and applied, and that it 



does not shrink on 



drying, thus making a 



water-tight seal. For 



greenhouse use, putty 



as bought in the gen- 

 eral market should be 



mixed with pure white 



lead at the rate of one 



part of lead to five of 



putty. This will stick 



to the bars and glass 



much better than will Fig. 59. Machine for dis- 



ordinary putty. tributing putty 



