50g of leaded (63/37) solder paste. It's worked great for making prototypes at Wayne and Layne headquarters, but this is not for production use.
It contains lead, and it was shipped to us in a cardboard box wrapped in tape, without any refrigeration. It seems to have an amazingly long shelf-life.
Solder paste, like solder, has some nasty ingredients in it. This is true of both leaded and lead-free formulations--so it isn't enough to get the lead out. You don't want to eat it. This is similar to solder wire, however, the particles in solder paste are small (25 to 50 microns for this stuff), and they can easily get on your fingers or under your fingernails. Many of the chemicals have no biological pathway to exit your body, so they just build up over time. It wouldn't be a bad idea to wear gloves, but make sure to wash your hands afterward. There's even special de-leading soap that isn't very expensive.
Seriously folks, be careful with your solder paste. You don't want your child or pet getting into it. Do not store the solder paste in a refrigerator that will ever store food or drinks.
When you've finished, clean your tools and work surface. Isopropyl alcohol works well. Don't throw your waste into the normal garbage can; dispose of it at your local hazardous waste disposal facilities.