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 
