Homebrew PCBs

On Tue, 11 Apr 2006 at 23:51:11 +0200, top-poster Ronald Vanschoren 
regurgitated:
>I just bought this thing:
>http://www.conrad.fr/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&storeId=10001&productId=221211&langId=-2&parent_category_rn=18948
>Not sure if it is pure NaOH, but I guess so. I says to solve it into 1
>liter of water and develop for about 1 minute.*
>*
>guja wrote:
>
> >7-10 g NaOH in 1 liter!
> >
> >Ronald Vanschoren <yahoogroups@...> wrote:    .....
> >  I developed the PCB in a NaOH solution (1 liter for 35grams NaOH).

Reading this backwards, as required by Ronald...

[ guja deserves part of the blame ;-)
   but at least they trimmed their quotes
   - except the group links :-(( ]

...Ronald first says that he used 35g/litre NaOH then,
when challenged to use only 7-10g/litre,
Ronald admits to using CRC "revelateur en poudre 1442"
which he 'guesses' is pure NaOH.

But (a) it's not 35g, it's only 30g
and (b) it's not 'pure NaOH' - it isn't _even_ NaOH'  at all !!

It's 100% disodium metasilicate.

Hint: when unsure of a commercial product,
search for a MSDS (Materials Safety Data Sheet), like
http://www.crcind.com/wwwcrc/msds/BB4031442-3.htm .

Sodium metasilicate is commonly used in laundry products
because (AIUI, IANAChemist) it dissociates into a highly
alkaline solution (pH 12.6 at 1 % concentration) but, unlike
NaOH, it does not decay in storage by absorbtion of
atmospheric carbon dioxide.

So 35g/litre NaOH is a different animal from 30g/litre
"revelateur en poudre", with a much bigger bite.

But what would you expect from a top-poster :-P

Sorry, Ronald, only joking - anyway, we'll be rid of you
after you self-medicate with a proprietary cold remedy
_and_ paracetamol tablets ;-) The chemistry does matter!


Regards, LenW
-- 
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