34 PRACTICAL TREE REPAIR 



For the little odds and ends petty injuries 

 and quickly-healing wounds a thorough daub 

 of tar is quite sufficient. But the strong color and 

 staining quality of tar must not be permitted to 

 lead to careless work with it. It must be flowed 

 on with a full brush, and every particle of the sur- 

 face must be covered. 



Observation of the poor results obtained from 

 the use of paint and tar, in the way they have been 

 used, has naturally brought about a search for 

 better materials. A number of " pruning paints " 

 have been put on the market and many others are 

 being tried on a small scale. The Ohio Experi- 

 ment Station has undertaken a systematic study of 

 the various dressings. These experiments are 

 hardly likely to result in the discovery of a better 

 material than good coal tar, properly applied and 

 renewed. But, as a matter of fact, tar dressings 

 are not properly renewed, and these efforts to dis- 

 cover a material which does not require frequent 

 renewals are thoroughly justified. They have, 

 indeed, already given us several dressings which 

 are superior to tar in this important respect. 



The new materials are mostly forms of asphalt. 

 Asphalt is a fairly pure solid bitumen resulting 

 from the natural or artificial distillation of petrol- 

 eum which, like western petroleum, has an asphalt 

 base, as contrasted with those forms, such as our 

 eastern petroleum, which have a paraffine base. 



