The white residue you refer to is actually pure silver. The acid
depletes the alloys at the surface leaving a fine silver.
There is no easy way to finish a piece with lots of detail or
texture. You have several choices to complete the task before using
You can test some of the 3M bristle disc wheels on a piece to see
how that works. You could also use a small bur or tapered steel rod
that has had the tip polished and use that as a burnishing tool with
a flexshaft machine or by hand.
If the texture or detail is not too deep you may also want to
experiment with a tumbler and different size and shape media.
And finally you can lightly heat the piece and use one of the silver
oxidizers on the market to darken the low areas. These oxidizers do
not work well on pure silver so you will need to heat the piece with
a strong light bulb, alcohol lamp or torch.
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