Homebrew PCBs

On 7/16/2013 11:40 PM, Kerry Koppert wrote:
>
> I live in a small largely agricultural country any chemical is difficult
> to obtain (unless it has a household or agricultural use). I'd like to
> try hydrochloric acid and hydrogen peroxide as an etchant and I can buy
> HCl in the hardware store (for cleaning concrete) but H2O2 is a little
> more difficult $25 / litre for 35% plus hazardous goods freight from
> 300Km away.
>
>
> _
H2O2 is available at 3% concentration in drugstores (pharmacies) as a 
topical antiseptic should be cheap - here in the US it's about $0.95 per 
pint.  It is also available at beauty store suppliers at up to 30 volume 
(~12%) concentration as a hair bleach - again, here in the US my last 
quart of 30 volume was ~$5.00 .  35_*%*_ sounds dangerously strong - 
that might be the reason for the hazmat charge.  Earlier etchant 
formulations  seem to run 1 or 2 pints of 3% H2O2 to 1 pint of 35% HCl 
(muriatic acid),  if I remember correctly.  It would take only a couple 
of */ounces/* of the 35% H2O2 to a pint of acid.

  Also - for safety, remember that the H2O2 is basically water, and "add 
acid to water, just like you ought'er!" .  Adding water to the acid can 
cause a dangerous exothermic reaction and splash the nasty stuff around 
(OK, you all know this, but safety first!).

Norm


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