The only safety concerns are your skin and eyes. That cream is pretty potent stuff. I haven't been able to find anything official, but anecdotal sources say its in the range of 15-20% peroxide. You definitely don't want to get it in your eyes, and it will burn your skin if you don't wash it off within a few minutes. It is a mostly safe procedure. You pretty much just paint on the cream with a brush and wrap the object in Saran Wrap to keep it from drying out. I also paint the inside of the Saran Wrap with the stuff so it stays extra gooey. Then plop it out in the sunshine or under the blacklight for awhile. Sunlight is far faster, but less predictable. 8 hours of sunlight is about the same as 24-28 hours under the blacklight. I imagine an unfiltered UV lamp might work faster, but those can be dangerous if used improperly. It's only time, and it's not like I can't go off and do something else while it cooks. 8 hours of sunlight is about all it takes to get the desired results. If it gets streaky or isn't quite done, you can just do it again. It's pretty hard to mess up.