How to distinguish the pure silicone oil and ungra...

Silicone rubber has been widely used to a lot of  fields for making silicone molds and other silicone products. But there may appear such problems like silicone mold oily in the process of making molds.     　　First,the molding silicone rubber itself doesn’t contain any oil,so it won’t be oily.If the mold is oily, it may be because you add the compound silicone oil (the compound of silicone oil and white oil).The white oil is not silicone oil but a kind of petrochemicals.   　　But how to distinguish the pure silicone oil and ungraded silicone oil?   　　1.Check by your observation:pure silicone oil is a transparent liquid without any smell,but  ungraded silicone oil smells bad and in a turbid liquid form.   　　2.To test it by fire.Take the pontil or glass rod to dip some liquid oil,if it can be lighted and fumed when burning,so the liquid is the ungraded silicone oil,which is a kind of petrochemicals.And pure silicone oil can not be fired,which is colorless, odorless,clear,nontoxic.The burning point of pure silicone oil is 320℃,but ungraded silicone oil is 100℃.   　　3.Freezing point method:Take 100g of two kinds of silicone oil into refrigerator at the same time.Under temperature of -5 to -10C for 2 hours,ungraded silicone oil will turn to turbid or frozen,while pure silicone oil is still clear and transparent as before,and it will not freeze until -5℃.