There is an old thread on this subject but I was warned to start a new so here it is.
I was about to toss a batch of Radio Shack Ferric chloride because it turned into a nearly sold mass after the last use.
Giving it some thought, it occurred to me that as I was etching at 140F, it might just be a matter of water evaporation.
I ran across this old thread that talks about adding concentrated acid and hydrogen peroxide to replenish.
No sure if both are a good idea but as I was in need of water it seemed like weak acid and peroxide would be just as good.
I set up an experiment using strips of PCB and a 40 ml sample of etchant held at 120F.
I timed the pieces to first effect and clean.
The 3 experiments were:
1 old stuff
2 added 25% battery acid
3 added 25% HO 2%
The results were the same for all, i.e. 4 min and 7 and about the same as when new.
The only difference is that when cooled to 60F, it did not crystalilze.
So I guess I fixed it but before "fixing" the whole lot, I would like some comments on what I did and/or what I should have done.
Thanks,
Jack