SNOWDROP

I could do with some help on this one. I found a piece of black card to photograph the snowdrop against, but then when I looked at the result it was not as dark as I had hoped. I altered the background in Picasa but that reduced the size considerably, and therefore presumably the quality. The image started at 893kb and is now only 217kb. What am I doing wrong, and is there any other way to produce a black background. I tried adjusting it in my ancient edition of Photoshop too but with the same result.

Apart from this, and breaking the toilet flush while trying to mend it, it's been quite a good day. And there's roast chicken tonight which is always a good thing. Happy days.