It is well known to enthusiasts that a glass must be "beer clean" -free of any grease or skin oils, including fingerprints-to support a good head of foam.
The presence of exogenous surface contamination, including dirt, grease, free iron from contact with steel tooling, and so forth, may interfere with the formation of the passive film.
外生的表面污染,包括:尘土、油脂、来自钢铁加工的游离铁等等,可以影响到钝化膜的生成。
3
The surfaces to be joined must be clean and free from oil, grease and heavy oxides.