Homebrew PCBs

I normally top post, but because you helped me so much I'll write it at 
the bottom especially for you :-p

Len Warner wrote:
> 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
>   
Ok should have looked into it better, I just trusted the guy who sold it 
as he said it was NaOH (I should have had a clue about his competence 
when he first tried to sell me etchant). But it _is_ 35gr as you can see 
on the package if you click this link

http://www2.produktinfo.conrad.com/datenblaetter/50000-74999/065226-an-01-fr-T_sachet_revelateur.pdf

Not that it makes much of a difference though.

Actually it's a good thing that it's the metasilicate stuff (I think), 
because I read on some places on the net that it is hard to overdevelop 
using metasilicate. What are your ideas/experiences on this?

Thanks for pointing it out.


Ronald