Adventures with Saffron

I went to Penzey's in Minneapolis, bought saffron and two kinds of cinnamon (I was out). If you are ever in the area, go, if only to smell. It's a wonderful place.
I bought the cheapest saffron they had, Spanish Superior saffron, at $6.79 a gram. I only used a little over half.
After getting some advice from Despina and from a few websites, I went for it. I tried two different mordants, vinegar and salt. I used two cards of white Splendor 100% silk, a 12 ply 8 yard skein which I cut into four lengths of about 2 yards each. This is the same brand silk thread I use for all of my blackwork. I soaked each skein in about a gallon of water, with some amount of salt and some amount of vinegar. I didn't measure, I just poured some in. I had to dissolve some of the salt by stirring but the water was warm so that worked fine. While each skein was soaking, I made a little gauze bag to put the saffron in so it wouldn't stick to the silk and cause darker areas on where that might happen.
The next step was boiling and stirring. This is the most boring step but it made my apartment smell really good for 3 hours. Each sample was boiled with the same water for close to an hour and a half. For the salt mordant skein, I added a second little gauze bag because it was paler than what I wanted. After each skein was finished boiling they were rinsed in warm water and hung up to dry overnight. While rinsing, I noticed that the vinegar mordant skein not only turned out darker (think on the lines of Northshield gold), but was extremely colorfast. It was the opposite with the salt mordant skein. In the past when I've painted different fabrics I've done heat setting and I thought about trying that to see what would happen. I'm told even the darker yellow will fade with exposure to UV light, but I'll need to wait and see about that. For now I'm keeping the silk in a dark place (my filing cabinet). Someone is going to explain why one skein is lighter and one is darker, and what exactly the vinegar and salt did. I'll take notes and post that here, but if anyone knows, feel free to comment on why that happened.