Homebrew PCBs

Malcolm Parker-Lisberg wrote:
>  
>
> Make your own tin electroless tin plating solution, see:
> <http://www.voodooengineering.com/index.php/tinning/87-diy-tin-plating-solutiion>
> All chemicals available on ebay
>
That page lists the components as

    * 0.5g Stannous Chloride
    * 2.0g Thiourea
    * 3.0g Sulfamic Acid
    * 100.0 mL Distilled water

and further down that the proportions don't seem to be very critical.  
Aside the fact that Thiourea seems like quite a nasty thing, the 
Wikipedia does have this...

~~~
Silver polishing

According to the label on the consumer product, the liquid silver 
cleaning product TarnX contains thiourea, a detergent, and sulfamic acid.
~~~

Come to think of it, I vaguely remember that this might have been looked 
into by somebody previously.