Homebrew PCBs

There was a bit of discussion about AP a while ago and now that I 
have had about a month of experience with it, I thought I'd report 
back.

I had a number of misgivings about AP based on comments posted here 
but since I had bought it, I figured I'd use it...

My set up.  A vertical tank that holds 1 L, a heater that brings the 
temperature to 100F and a bubbler.  All my boards have been double 
sided so there was lots of copper to etch.

Issues that had been raised:
- short shelf life of AP solution.  I've been pouring it out of the 
tank and storing it in a glass jar.  So far i have done 12 boards and 
it appears to be still quite potent after a month.  The last board 
etched in about 13 minutes, just like the first one.  I did have a 
huge crystal (Cu sulfate?) form in the bottom of storage jar.  Kind 
of pretty.
- toxicity/fumes.  While I haven't been making cocktails with it, I 
can say that I've experienced no problems or skin irritation.
- cost.  ya got me there, its about twice the cost of FeCl

Some of the benefits of AP:
- clear. I can easily monitor the progress of the etch.
- non-staining.  I spilled a little on a wooden benchtop and some 
paper.  neither took more of a stain than water.
- the powder is not exothermic when mixing with water.  FeCl is 
really nasty that way. (I'm sure I'm using the incorrect term here, 
it releases a LOT of heat when mixed with water)
- I believe it has more etching capacity than FeCl.  I've done twice 
as many boards as with my last batch of FeCl (1 L, too).  This is a 
subjective opinion and could be completely false...
- pretty blue color

If I had to get some new etchant today, I think I'd experiment with 
HCl+H2O2 but AP is a fine etchant to use and I'm very happy with it.