Ferric Chloride
By Jeremy Clapham
Very useful stuff for preparing brass for working on, decrapinating pennies and
making etched brass signs. All in all it's lovely stuff, but don't put it in your tea.
I first came across this stuff twenty years ago when I was on the fringes of a group
that collected and restored old stationary engines. They were using it to bring old brass
that had deteriorated to the point of looking blackish green back to a shiny gold lustre.
By trial and error I discovered that you need to handle it carefully and use it sparingly,
otherwise the piece you're working on shrinks before your eyes and your fingers look
like you've been smoking sixty Woodbines every day since you were born. There are
other warnings, and I list them here because I want to be responsible, but don't let me
put you off buying it, especially if you are into restoring old machines. It also goes by
the names of Chloride Hexahydrate and Ferric Trichloride Hexahydrate. The Material
Safety Data people describe it accordingly:
Health Rating: 3 - Severe (Life)
Flammability Rating: 0 - None
Reactivity Rating: 2 -Moderate
Contact Rating: 3 - Severe (Corrosive)
Storage Colour Code: White (Corrosive)
Lab Protective Equipment: GOGGLES & SHIELD; LAB COAT &
APRON; VENT HOOD; PROPER GLOVES (Proper gloves???? ..... eh)?
Having just read that this is nasty stuff and to be handled only when dressed up like a
refugee from a mad professor film, it might seem curious that anyone can buy it. When I
first bought some back in the 1980s, although nobody questioned why I wanted it, I did
have to sign the poisons book in my local branch of Timothy Whites' (remember them)?
However, in these enlightened days it's much easier. You can buy it in liquid form from
Tandy the electronics hobby store (also known as Radio Shack) or Maplin Electronics,
which have 114 stores nationwide. They sell it in little dried rocks, looking a little like (I
suspect) crack cocaine (only a guess).
So what's it used for? Well, Tandy and Maplin is a bit of a clue. The electronics
lads use it in the manufacture of printed circuit boards (PCBs ). The PCB starts off as a
sheet of fibreglass with a thin layer of copper. Using transfers, they outline the route
they want the circuit to go between the components, and then the whole thing is dunked
in Ferric Chloride. Within a short period (depending on the strength of the solution), the
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