Homebrew PCBs

The only way to know how "strong" your CuCl etchant is, is to use a
hydrometer.  The copper makes the solution more dense, by measuring
the density you can determine the copper concentration.

See http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/
for all the details.

Note: my solution looks like the photo at the top of Adam's page.

"Spent" etchant is opaque BROWN.  This may look like dark green at first
because it's mixed, but see Figure 5 on Adam's page.