2 08 NEBRASKA STATE HORTICULTURAL SOCIETY 



tree by being absorbed. The writer doubts whether this supposed 

 injury is serious enough to receive consideration and the material 

 has tlie advantage of being cheap. 



Gas tar is the residue from the manufacture of gas. It is inexpen- 

 sive which is in its favor, but it has the disadvantage of being almost 

 entirely absorbed by the wood and as it is like coal tar contains some 

 volatile matter which may be injurious to plant growth, it may do 

 some injury to the cambium of the trees. No injury, however, has been 

 done in our station orchard. The greatest disadvantage has been 

 that, the tar being absorbed, allows the wood to check which is of 

 course very undesirable. 



Asphaltum is a byproduct manufactured from the residium in 



the distillation of western petroleum. According to the stage to 



which this distillation is carried on the melting point will very from 



200 degrees to 285 degrees F. This is the only essential difference 



in the different grades. 



All tlie above grades must be heated before they can be' applied. 

 For this purpose a charcoal heater or a gasoline tinner's stove is very 

 satisfactory to maintain the required temperature in the orchard, 

 but the asphaltum must first be melted over a hotter fire. The hot 

 asphaltum is applied by means of an old brush or swab and smoothed 

 •ip with a piece of hot iron either flat or curved according to the sur- 

 ''ace of the wound. 



Solid asphaltum makes a good cheap cover, but it is hard to apply 

 on account of its having to be heated. Then there is some danger of 

 tracking during the winter months where it is used on large wounds, 

 unless carefully applied. If the work is well done solid asphaltum 

 makes a very effective cover. 



Liquid Asphaltum. This is solid asphaltum dissolved by mixing 

 it while hot with some substance such as gasoline or naphtha when 

 It resembles very closely coal tar, and there are the same objections 

 advanced against its use as against coal tar. The vise of vegetable 

 oils as solvents have been recommended to overcome those objections, 

 but these oils make the product more expensive. Both forms of liquid 

 asphaltum have been used at the Nebraska Experiment Station with 

 good results. 



The Standard Oil Company offers a solvent called "Varmolene" 

 for making liquid asphaltum. To make liquid asphaltum by using 

 gasoline, naphtha or "Varmolene"' the asphaltum is melted, then 

 withdrawn from the fire and stirred while the solvent is added. The 

 amount os solvent to use will depend upon the melting point of the 

 asphaltum and the desired consi?cen(;y of tli'? mixture Ff)r winter 

 use where the asD^'i' tum has a me'cin,:^- point of 2S.t degrees F. two and 

 one-half pares of oW may be v.se.l to oni^ p:irt of ospliallum. In 

 summer the proportion shoui''' bo about two to one. Vegetable oils 

 ni.sy b'^ e-T3ployed ::■? solvents in whicii case slightly less oil is asod. 

 When the solvents are added to hot asphaltum there is some danger 

 cf explosion if nea" thf fire. 



