[schmidling]

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





 

[Ballistic]

I think you are over complicating it, as Ferric Chloride is hygroscopic and if left with the lid off will turn to liquid in short shrift.