Soap must be considered non-kosher unless it is certified kosher.  Soap without kosher supervision should not l'chatchila be used on food utensils--even if you use cold water and even on glass--because a soap residue adheres to the surfaces, even after careful rinsing. 
Soaps/Detergents
Bar soap is generally made from animal fat. Since all soaps do have taste and might be edible by a dog, they might not be nifsal for a dog and therefore cannot be used on eating utensils.