^0 " MASSACHUSETTS HORTICULTURAL SOCIETY. 



failures kuowu. Various patents for metal sash bars have from 

 time to time been issued, and judging from the claim of superiority 

 made by the venders, perfection in glazing has been reached. 

 There is a sentiment entertained by some, particularly those who 

 do not know the special conditions to be met in glazing a green- 

 house, that metal is more lasting than wood, but a little considera- 

 tion of the subject will serve to show why so little success has 

 been achieved in this style of glazing. It will be shown by an 

 examination of any so-called puttyless glazing that it is not tight, 

 or if tight when first erected it has not remained so. If a soft 

 metal like copper, lead, or zinc is used, it has no elasticity and 

 when expanded by the heat it does not contract again to its former 

 shape, and in a short time the metal sags away from the glass 

 until there is a considerable opening along every joint. These 

 metals, including galvanized iron, are not, when rolled out thin 

 and subjected to the conditions of a greenhouse roof, as durable 

 as wood. All these metals have great conductivity of heat and 

 cold, causing a large loss of heat when used as sash bars, whereas 

 wood is one of the best non-conductors. It is impracticable to 

 set glass without the use of putty or its equivalent, either in wood 

 or metal bars. Common sheet glass has a concave side and all the 

 edges of each light are more or less curved, so that to clamp them 

 down to straight lines between two pieces of metal or wood, as is 

 done in every method of glazing without putty, breaks many lights 

 while the setting is being done and is followed later by more 

 breakage as the glass is subjected to any additional strain. The 

 larger the size of the lights used, the greater will be the curves 

 and consequent breakage. By bedding the glass in putty these 

 inequalities in the lines of the glass are allowed for and there is 

 comparatively no breakage. The bars should have V shaped 

 rabbets so that the putty cannot work out. By the use of proper 

 machinery the spacing for the glass can be made so perfect that 

 Avhen the outside of the bar is painted the glass cannot be removed 

 witliout first scraping off the paint. The best glazier could not 

 make a good job of glazing on a roof where the spacing has been 

 carelessly or improperly done. Much depends also on the quality 

 of the putty used. The best is made from kiln dried and bolted 

 gilder's whiting mixed with pure linseed oil. As the wholesale 

 price of the best putty in the market is generally quoted at less 

 than the first cost of the honest ingredients l)ought separately, it 



