The only condition is that they should have no paint and oilspots and burning marks.
唯一的一个条件是：这些轮胎没有任何涂染、油污以及燃烧的痕迹。
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Even if you can't see any stains, it's possible that lingering oilspots will oxidize and become noticeable (and permanent), so keep that in mind when deciding what needs washing.
It is alsodesirable to be used for removing heavy oilspots off polyester, cotton fabrics or polyester silk imitations in alkali bath, as well as for pretreatment of oily silk yarn.