The researchers wanted to find a color that hinted at the soap’s “unparalleled grease-cutting power,” Eberhard tells us, and ...

Microwave for 30-second cycles, checking at the end of each cycle until the glycerine soap base is completely melted. That's it! Now, you can add colour to the melted soap base to colour it.

The firm started by making starch-related products but soon branched out to include washing blue and blacklead for grates. Reckitt's Blue is an iconic product of the firm. In 1879 the company ...