Bleach is usually used to create an aged surface. It starts differentially on the metal depending on pits, polishing scratches, grain flow, etc. and gives what amounts to an uneven surface somewhat like you would get through corrosion over time. French greying if done appropriately gives a very even surface. You can take finely engraved parts, do a French grey and not loose details of the engraving. Boiling in bleach would have drastic effects on the engraving, none of them good. Although I've done lots of rust bluing on high end projects, both traditional and modern, I've not rust blued before doing a French grey like David did. as rust bluing can create more microscopic pits in the surface than would be desirable for a fine French grey on an engraved, high grade firearm. On the other hand, such surface texturing was entirely appropriate for David's project. The whole point of the initial bluing, whether it is a rust blue, hot caustic blue or good cold blue seems to be to provide a chemically bound surface that the acid etch will work on very uniformly.
Tom
