Well, I played around with different solutions of latex and paint and finally came up with one that gave a nice opaque black once it had dried. I tested it on some sample glass (Yes, I actually own sample glass) and the results were mightily impressive. Now the dilema. There seems to be a certain swing in opinion regarding the 'correct' phase of the moon in which one should create a black mirror. Older books regard the new moon as the optimal time whilst newer sources seem to prefer the full moon. The only reasoning for the difference seems to lie in what outside influences may affect the creation of the mirror; for example the lack of pure light during a new moon might invite devils to hide in my mirror. Well, what's so bad about that. I'm all for equal opportunities. Anyway, i'm going with my gut and my gut says: new moon.
The next one happens to be on the 4th of November at 8.35pm. So, not long to wait. I might make a few mirrors seeing as i'm mixing up the latex. You know for Christmas gifts or maybe for selling...