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Copper etching with hydrochloric acid


#1

Hi All

I am new to this forum and I will pose this question

I have been using ferric chloride quite successfully to etch copper
jewellery, however it has been reclassified in New Zealand as a
dangerous good and my old supplier will no longer carry it and is
available only in commercially in large quantities through other
suppliers. So I had a look on the net for alternatives and found
computer circuit board etchers were people that needed the same
effect as jewellery etchersand had explored other options. ammonium
persulphate was one but what interested me was a mix of hydrochloric
acid and hydrogen peroxide that was reusable and looked like it gave
a very clean etch. however it seems to etch very fast which is never
good if you want to avoid undercutting. Has anyone tried this with
copper jewellery? and what depth of etch can you get?

I patinate the etched area with liver of sulphur and a clear
distintion between patinated (blackened) copper and plain copper is
needed, hence a the deeper the etch the better.

Thanks Chris


#2

If it etches too quickly to suit you why not just reduce the
concentration with water until it etches at the speed you’re looking
for?

Mike DeBurgh, GJG


#3

Hi Chris,

The chemical classification situation is like a revolving door. But
you can easily procure ammonium persulphate over the counter in NZ
in small quantities. Just visit your local branch of Jaycar
Electronics who you will find keep stock of it as product CAT. NO.
NC4254 in 400 gram jars for about NZ$15.

Just look at http://www.jaycar.co.nz to find the nearest store and
search on “persulphate” to get an easy result. They, too, no longer
keep ferric chloride.

Mark B
Fourth Axis
http://fourth-axis.com/four-4-jaw-chuck-jwx-30/


#4

Google saltwater etching. You don’t need any acid to do it just salt
and a source of DC current like a battery or battery charger or DC
power supply.

Works on copper and steel just fine, it will not work on silver
though.

James Binnion


#5

Salt water and a D battery work great. You need to put the battery in
a holder with leads from each terminal. Connect your anode (+) to a
copper wire attached to the piece you want to etch, and your cathode
(-) to a copper wire connected to the plain piece. Submerge both
pieces in a saturated solution of kosher salt and distilled water,
vertically. You’ll get a better etch if you have a bubbler at the
bottom of the container. I use an aquarium pump and an airstone. Let
run for about an hour, and check your depth. This works on copper,
brass, nickel, and bronze, as long as the two pieces of metal are the
same.

Good luck.
Emie


#6
however it seems to etch very fast which is never good if you want
to avoid undercutting. Has anyone tried this with copper jewellery?
and what depth of etch can you get? I patinate the etched area with
liver of sulphur and a clear distintion between patinated
(blackened) copper and plain copper is needed, hence a the deeper
the etch the better. 

Oh Chris,

I thought I should mention a couple of unintended consequences that
may flow from etching with hydrogen peroxide and hydrochloric acid.
When a mixture of hydrogen peroxide and hydrochloric acid from
printed circuit boardetching is mixed with waste acetone from cleaning
the finished board and allowed to stand, you form acetone peroxide.
While amounts obtained this way are typically much smaller than from
intentional production, they are also less pure and prepared without
cooling, hence very unstable.

So you may possibly blow yourself to smithereens. Another result
could be your arrest and imprisonment, if the authorities get the
idea you are working with these common precursors in the manufacture
of MDMA.

So, here’s good luck to you! Now you know why I suggested the
ammonium persulphate route instead.

Mark B
Fourth Axis