When I made boards back in the late 70's I used ammonium persulfate
most of the time. Works good, no stains.
I have no idea if it's still readily available or where to get it.
Steve
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At 06:56 PM 7/2/2017, you wrote:
>I have been using ferric to etch boards for a while now. Recently I
>got lucky and came into a cache of 1973 vintage copper clad PCB
>stock, which will enable me to make some reproduction pieces that
>are pretty much indistinguishable from originals in terms of
>look. However, I have noticed that the ferric solution stains these
>boards, adding a yellowish tint. Is there any way to avoid
>this? Or clean it after?