36 VEGETABLE FORCING 



house, but this is generally very unsatisfactory. It is far 

 better to fill the rabbets with putty, and then squeeze out 

 the surplus putty by forcing the panes into place. 



Glazing points are used to fasten the glass, and when 

 the work is properly done the joints will be air and water- 

 tight. A matter of very great importance is often neg- 

 lected in greenhouse glazing. Every pane of glass is 

 curved. The panes must be laid with the curves always 

 up or always down ; otherwise there will be large air 

 spaces between the laps. When the sash bars are pro- 

 vided with drip grooves, the curve should be up; if the 

 grooves are lacking, the curve should be down. 



Shading. It is sometimes necessary to shade green- 

 houses. A cheap and rapid method of providing shade is 

 a thin whitewash made of air-slaked lime and applied with 

 a spray pump. Such a wash will adhere as long as it may 

 be needed, and there will be no difficulty in removing it 

 with brush and water. The green scum which often 

 forms on old greenhouses may be easily removed with a 

 spraying solution made by dissolving one pound of oxalic 

 acid in a bucket of water. A crystalline deposit will be 

 formed on the glass, and the first rain will wash it off. 

 The work should be done on a clear day. One pound of 

 oxalic acid is sufficient for 3000 square feet of glass. 



Painting. Immediately after the glass is laid, the house 

 should receive two additional coats of paint, and there- 

 after the interior and exterior should be painted often 

 enough to preserve the wood parts. Some growers paint 

 the outside of the house every other year, although most 

 of them paint at much longer intervals. There is some 

 difference of opinion regarding the value of subsequent 

 painting in prolonging the life of a greenhouse, but there 

 is no question about the value of paint in respect to the 

 appearance or attractiveness of an establishment. It is 

 exceedingly important to lead properly all joints when 



