blue carwash soap

[bosun]

Does anyone know what the blue stuff is that colours the soap in the commercial do-it-yourself drive-in carwashes? Stains your hands and clothes.

[bsrlee]

Its just blue dye, similar to what they put in regular washing powder. Only real purpose it has is to help tell who manufactured the stuff if something goes wrong & it needs to be tested - a LOT of different brands actually contain a generic product. As it isn't supposed to go on clothes in this case, they probably aren't really careful about which colouring agent they use.