208 Tanning Materials : Nomaison Process. 



the bark of all that can be obtained. It is first exposed to the 

 sun, with the inside up, for a short time, and is then piled with the 

 outer side up until dry. It is estimated that the trees yield about 

 five per cent of their weight in bark, and that the latter looses 

 about one-third of its weight in drying. 



834. Oak bark is much injured by rains, and even when care- 

 fully dried and housed it deteriorates by keeping. Quercitron (the 

 bark of Q. cocdnea) used for dyeing yellow, and for tanning, is usu- 

 ally ground and sold in sacks. Oak wood, when peeled, is used for 

 various manufacturing purposes, and for firewood and charcoal. 



The Peeling of Oak Bark by the aid of Heat. 



835. The inconvenience of crowding the work of peeling into a 

 busy season of the year, has led to the introduction of a process in 

 Europe, by the aid of which this work can be done at all seasons 

 of the year. It is known from the inventor as the "Nomaison Pro- 

 cess" The apparatus consists of several large iron receivers of thin 

 plate iron, strong enough to bear a moderate strain, and air-tight. 

 The wood is placed in these, and steam at about 170 centigrade 

 (338 Fahr.) is admitted from a boiler so placed as to serve several 

 of these receivers. They hold about half a cord each, and the 

 time required varies from an hour and a half to two hours and a 

 half, according to the season when the wood is cut. It is then taken 

 out and peeled. If the heat is continued too long, the bark again 

 becomes adherent. 



836. One great advantage to be gained by this process in the 

 working of coppice- wood is, that it is not necessary to cut the wood 

 at the season when the greatest injury is done to the stumps that 

 are to send up a new growth. Careful experiments have been 

 made by order of the French and Prussian governments upon the 

 quality of the bark thus peeled, with favorable results. It is men- 

 tioned in this connection as of interest with respect to the future 

 supplies of bark for tanning, as our native woodlands that furnish 

 this material become scarce. 



Sumac. 



837. The leaves of the sumac contain a tanning material much 

 used in dyeing, and in tanning light leather, and from six to ten 

 thousand tons are imported into the United States annually from 



