﻿28 BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 



Salt is of little or no value in preventing blue-stain in comparison 

 with the other chemicals. The application of salt after blue-staining 

 has well started is almost a waste of money. In fact, the application 

 of wet salt or a strong salt solution may prove detrimental in the long 

 run, for if the lumber is dried after such treatment the affinity of 

 the salt for water may cause the moisture content to remain much 

 higher than normal. 



Mercuric chloric! in a 0.1 per cent solution is exceedingly effective 

 against blue-stain, but on account of its highly poisonous nature 

 and extremely corrosive action when in contact with manjr metals 

 it is little used. 



Shipping green stock closely piled in closed box cars during the 

 spring and summer months is almost certain to result in severe stain- 

 ing. Indeed, the writer has seen some stock handled in this way 

 which stained even in winter. On the other hand, any measures 

 taken to prevent staining, such as open piling in gondolas or on 

 flat cars, will almost certainly result in severe checking. Of the two 

 evils, checking is by far the most serious in airplane stock, since 

 checked lumber is greatly reduced in strength, while the stained 

 lumber is only somewhat unsightly. Shipping green lumber in the 

 close hold of a vessel, particularly if tropical seas are to be traversed, 

 is an invitation to swift and sure disaster as far as sap staining is 

 concerned. It is doubtful whether dipping in any chemical solu- 

 tion now used, except possibly mercuric chlorid, would be effective 

 under such severe conditions. 



But, to repeat, the most effective measure to employ against blue- 

 stain is speed in drying the wood. Get the logs from the woods to 

 the saw with the greatest rapidity and the lumber from the saw di- 

 rectly into the dry kiln. 



SAP-STAIN ON SOFTWOODS. 



Certain species are peculiarly susceptible to sap-stain. This is 

 due both to the character of the wood and to the climatic conditions 

 of the region where the species grows. Western white pine, spruce, 

 and southern yellow pine, the last-named wood including longleaf 

 pine (Pinus palustris Mill.), shortleaf pine (P. echinata Mill.), and 

 loblolly pine (P. taeda Linn.) , are very subject to sap-stain, especially 

 blue-stain, while true fir and cedar are not so easily affected. Douglas 

 fir occupies an intermediate position. 



Besides blue-stain, a red stain has been very commonly found on 

 Sitka spruce airplane lumber. It occurred abundantly in the East 

 on stock in cars just arrived from the Pacific coast and also developed 

 on material along the Atlantic coast which had arrived unstained 

 at the port of embarkation but was held over awaiting shipment. 

 The stain appeared as terra-cotta or brick-red spots on the rough 

 lumber, varying from very faint to a pronounced color. In the stock 

 worked up in the factories in this country it was found that the 

 stain was superficial, usually surfacing out during remanuf acture ; 

 but reports from abroad indicate that the fungus developed very 

 intensively by the time the lumber reached European ports, and the 

 discoloration penetrated deeply into the sapwood. The appearance 

 of the wood is not marred to the same extent that it is by blue- 



