The shoeshiners cleaned the footwear and added an oily substance to protect the shoes' leather material.

鞋匠们将鞋子清洗干净，并添加了一种油性物质来保护鞋子的皮革材料。

Some people believe that Sarah studied the hair product she used and added her own secret substance.

一些人认为，萨拉研究了她使用的发用产品，并添加了自己的“秘密”物质。

These  fillers added substance to the dwindling food supply, even if they didn't add any nutrition.

这些填充剂为日益减少的食物供应增加了物质，即使它们没有增加任何营养。