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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