Homebrew PCBs

Just as an FYI I use Nitric acid, and have been doing so since 1987.
Fairly easy to handle at the lowish concentration in the etchant tank. I 
can handle the boards with bare fingers once I get them rinsed inside of 
10 seconds so I etch next to the rinse tub sink, although I generally 
use plastic tongs/tweezers.  My etchant tank is an ice cream container 
as nitric is plastic safe as well. No heating required, but minor 
ventilation is, it self agitates due to some bubbling during etching. No 
staining etc, clear liquid and does not degrade when dilute. Lasts for 
many years.

Harder to come by in the U.S.A. but if you hold a tertiary degree you 
can buy it from lab chemical supply companies. I am not in the U.S.A. 
and obtain it direct from my old University in carboyles.

I mix down the concentrated stuff to 1.2 Sp. grav to 1.22 Sp grav. for a 
fresh batch as required (acid adds to water). Resultant etch in 5 to 8 
mins double sided, 1 oz. Detail traces to 8 mils using the toner 
transfer/foiling method. No heating or agitation required. Suitable for 
quick and dirty sharpie marker traces, black or silver pens, silver is 
better. Black ink needs to be dried properly (hot air speeds that).

The waste is acidified copper nitrate which is  not a hazmat. Good for 
drain cleaning/sewer lines, anti fungal use etc.

Ancel