You can find about these etching chemicals used in
making printed circuit boards here and download MSDS sheets for
each chemical:
ferric chloride: http://www.mgchemicals.com/products/415.html
A. Stated as providing a more consistent etch than Ammonium Persulfate
B. Stated as etching twice as fast than Ammonium Persulfate
C. Roughly 10-20 minute etching time.
D. Will not remove most etch resist inks.
ammonium persulfate:
A. Translucent liquid allows the user to see the progress of the
etching process.
B. Roughly 30 minute etching time.
C. May remove some etch resist inks. Must use a compatible etch resist pen.
http://www.mgchemicals.com/products/410.html
sodium persulfate:
A. Flash point at 180 deg F. FLAMMABLE!
B. The solution is shock sensitive
C. Solution decomposes when heated.
D. Cleaner solution, allows increased visibility during etching.
E. Will not remove most etch resist ink.
F. Must be stored in a ventilated container due to gasseous nature.
http://www.mgchemicals.com/products/4101.html
Ferric chloride is cheapest- It is a byproduct of steel making (
spent pickle acid) it is a common coagulant used in municipal water
purification both for waste treatment and potable water.
for more see:
http://www.pvschemicals.com/techMSDS/PotableTech.doc
For more on etching mordants see from printmaking
sites: galvanic etching
http://perso.club-internet.fr/gravert/galvetch/contfram.htm
and
Edenburg etch ;
http://www.polymetaal.nl/beguin/mape/edinburgh_etch.htm
jesse