Homebrew PCBs

On 17/07/2013 7:16 p.m., Norm wrote:
>
> 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
>

Should is the operative word. In New Zealand make that $9.00 for 200 ml 
(about 1/3 of a pint).
>
> 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
>

35%, 3% still costs the same to transport, I've got plenty of water here 
already.

> 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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>
> 



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