Lou said:
The way Kurt is doing it would not work for copper based substrates without putting in certain agents that protect the copper from attack.
Even then, so Kurt understands, if you are not exceedingly careful with the reverse-AR, it can go to hell on you in a bad way.
Correct - it is reverse AR --- the process was given to me through PMs by another one of our most respected long time members & I was asked to keep it under my hat & because of my respect for this member I was not going to break the confidence he asked me to keep
However - now that Lou let the cat out of the bag - and - because I also received a PM with this link
Anyone came up with a technique or process for watch bands ? --- its not really a secret - its just not a well known &/or discussed process
It is just what it says - AR in reverse & it works very well on SS gold plate &/or gold filled - however - there are a few down sides to it
As Lou said "if you are not exceedingly careful with the reverse-AR, it can go to hell on you in a bad way" (ask me how I know :lol:
:lol: )
First you don't want to start with to much HCl & then be "very" careful with following additions - if you start with to much HCl &/or over do additions it will attack the SS & you just started a mess - if you "exceed" the HCl "limit" you have a mess --- also - NO heat - warm is ok (which is why I was working out in the sun) but no real heat
Nitric does not react with SS (which is why it comes in SS drums) but HCl does - so you need to control the HCl in a manner that the nitric keeps the SS passive allowing only the gold to be dissolved - to much starting HCl &/or additions & or heat will cause the HCl to go to work on the SS & then you have started the gold in gold out cementing process - you need to let your "starting" HCl become "loaded" with gold ions & then you can make addition of HCl to dissolve more gold - but only to a point so that the HCl does not over come the nitric keeping the SS passive
This means that your ending AR solution has "
a lot" of free nitric - that means a ton of sulfamic to de-Nox - or burn up a lot of copper to cement - or drop with hydrazine sulfate
Having access to &/or the price you pay for nitric is another factor
How I did the 8 lb batch the other day
Start - 2 beakers - 1 lb SS/GP each --- 400 ml nitric 12 ml (3%) HCl --- let react so HCl "loads" with Au - make 2 additions (per beaker) that brings HCl up to 5% --- decant - rinse/wash SS to another beaker (first lite rinse goes to decanted beaker - rest goes to another beaker)
Take decanted AR solution (started with 400 ml nitric) - ad 6 ml HCl (1.5%) ad to next 1 lb SS - make 2 additions HCl of 1.5 to 2 ml each addition
repeat that once more - (I went twice more but was gritting my teeth on exceeding the HCl on the 4th go round - but no problem) :mrgreen:
pour all rinse water in with main AR solution & evap back down some - recover gold as you prefer
Kurt
Edit to ad; - when I talk about using this on gold filled above - I am of course talking about gold filled SS