Homebrew PCBs

I'm having a tough time finding ferric chloride. Pretty tough to imagine in 
a large metro area (Chicago), but TV retailers is all I find under 
Electronics in the yellow pages. If I buy bulk anhydrous, what dilution 
should I make the working solution? I saw 40% by weight on MG's website and 
other places. (What, exactly, is a Baume? as in: "To form the basic stock 
etching solution, water is added in the ratio 2 parts water to 1 part ferric 
chloride solution in a solution strength of 42\ufffd Baume.") 
(http://www.polymetaal.nl/beguin/mapf/ferric_chloride.htm).

On Fri, 04 Nov 2005 11:03:45 +0100, Mike Young <mikewhy@...>  
wrote:

> I'm having a tough time finding ferric chloride. Pretty tough to imagine  
> in
> a large metro area (Chicago), but TV retailers is all I find under
> Electronics in the yellow pages. If I buy bulk anhydrous, what dilution
> should I make the working solution? I saw 40% by weight on MG's website  
> and
> other places. (What, exactly, is a Baume? as in: "To form the basic stock
> etching solution, water is added in the ratio 2 parts water to 1 part  
> ferric
> chloride solution in a solution strength of 42\ufffd Baume.")
> (http://www.polymetaal.nl/beguin/mapf/ferric_chloride.htm).

Well, you are looking in the wrong place! Look for chemicals not  
electronics.

I dunno about the dilution, i mixed it according to package (mine came  
 from a electronics mail-order).

Baume is some nasty scale for concentration i think, dunno why one would  
prefer it over %, ever.

ST

Purchase an inexpensive hydrometer which is used to measure the
specific gravity or Baume. You can mix the ferric chloride with water
until the specific gravity is correct according to the hydrometer. You
can also monitor the copper loading of the etchant by taking specific
gravity readings. The specific gravity reading will increase as more
copper is etched. 

I purchased my set of hydrometers many years ago and at that time they
were less than $10 USD each. They are very similar to the small anti
freeze testers sold in automotive stores. If you had a fresh etching
solution of known strength you could use it to calibrate your own home
made hydrometer. After calibration it would be simple to make up new
solutions as needed.

Tom

--- In Homebrew_PCBs@yahoogroups.com, "Mike Young" <mikewhy@s...> wrote:
>
> I'm having a tough time finding ferric chloride. Pretty tough to
imagine in 
> a large metro area (Chicago), but TV retailers is all I find under 
> Electronics in the yellow pages. If I buy bulk anhydrous, what dilution 
> should I make the working solution? I saw 40% by weight on MG's
website and 
> other places. (What, exactly, is a Baume? as in: "To form the basic
stock 
> etching solution, water is added in the ratio 2 parts water to 1
part ferric 

> chloride solution in a solution strength of 42° Baume.") 
> (http://www.polymetaal.nl/beguin/mapf/ferric_chloride.htm).
>