Stray thoughts, too late for the solstice, but here goes.
Fogginess may be part of the nature of the beast.
Did you gauge the fogginess by looking at the neg or doing a scan? Looking at the image after scanning may make it look better and bring out the color.
The paper you use will have a huge impact on what the image looks like. See this link: http://www.greggkemp.com/projects/pa...or-solargraphy A rule of thumb is to use multigrade paper and not graded paper.
Do you live in a snowy climate? Six month solargraphs where I live are likely to have between four and ten weeks of snow cover on the ground. This can lighten an image, to say the least.

And best of luck with the solargraphs. They are fascinating and often a pleasant surprise.