SOLE LEATHER 57 



the early liquors in tanning should be more acid than for 

 other leathers. With old methods of tanning one could 

 trust to the natural sourness of the liquors to complete the 

 deliming and replump the goods with acid. In such cases 

 any deliming was also unnecessary. In the modern yard, 

 however, we get " sweet " liquors coming down the yard, 

 partly on account of the greater proportion of extract used 

 and partly because the liquors themselves are not so old. 

 Hence it is now practically always necessary to acidify 

 artificially the tan liquors. This may be done by adding 

 a few gallons of lactic, acetic, formic, or but^rric acid to the 

 handlers and suspenders, especially in the winter and spring. 

 It is now increasingly common to place sole butts in a 

 special acid bath after they have been in tan liquor for about 

 a week. This bath is often made from sulphuric acid, and 

 may be I or 2 or even 4 per cent, in strength. 



The actual tanning of sole butts lasts three to four months, 

 and just prior to the war the tannage consisted often of about 

 one-third myrabs, one-third valonia, and one-third extract. 

 The myrabs and valonia were leached together, and the 

 extract added to the best leach to make layer liquors of the 

 required strength. Some mimosa bark was generally used 

 also, and now it is extensively employed to replace the 

 valonia. The most widely preferred extract is chestnut, 

 but quebracho, myrabs extract and mixtures have also a 

 prominent place, and mimosa bark extract an increasing 

 importance. It is recognized that this tannage is if any- 

 thing too mellow, and that if only a smooth grain and plump 

 butt an be ensured in the first weeks of tanning, it is much 

 better for sole leather to employ the most astringent tans 

 possible and the sharpest liquors (i.e. liquors with a small 

 relative proportion of soluble non-tannin matters). Hence 

 there is the tendency in sole-leather tanning to employ 

 fresh clear liquors for the butts and use up the more mellow 

 liquors on the " offal " (shoulders and bellies). 



Four types of sole butt tannage will now be described, 

 all of which illustrate the methods employed in a modern 

 mixed tannage. 



