My questions are:: How many times can one use the same batch???
You can use the solution repeatedly, as long as the pieces are not
sitting in the precipitate. However, as the solution works (etches)
it does lose strength. You can freshen the strength by adding dry
crystals. I allow my solution to settle out occasionally, decant the
liquid from the precipitate (solids), and add fresh crystals to bring
the solution up to 15-30 degrees on the Baume hydrometer.
Is there a shelf life for Ferric chloride??
I'm sure there is, but I've been using the same solution, with
addition of crystals or distilled water for my specifications since
Can it be that mine was old???
I don't think age has as much to do with it as much as strength.
Keep it in a tightly sealed container and in the dark. It does have
components of chlorine that can be affected by sunlight and/or heat.
What about the strength. Does ferric chloride come in different
Strength of the solution definitely plays a part in how well the
solution etches. A stronger solution etches quickly, but can leave
striations in large open areas. A weaker solution will etch more
slowly, but can lead to undercutting of fine pattern lines.
You can get ferric chloride crystals from a chemical supplier in a
large city (may have to complete a form telling how it will be used
and documentation), or from an electronics supplier, such as Jameco.