The size of the magnifying glass is the important attribute for solaring, not magnification strength. A larger diameter lens means more surface area to collect the light which is focused into a point. More light equals more heat. I think the magnification strength changes the distance of the focal length, with higher power lenses having shorter focal lengths. I have a 30x loupe myself (for looking at trichomes!), and it is not useful for solaring. I've used a 5x 3-inch magnifier from the reading glasses rack at Walmart with great success, and my current lens is about 3 inches diameter as well, from inside a rear-projection television. I love solar smoking/vaping. I spent an entire summer solaring when I first tried it a few years ago. Way preferred to butane, but of course my vapes see the most action these days...still, there is something very majestic about directly using the sun's energy to get high. And you'll find clouds improve your patience.