This is a question that has actually come up a couple of times in the last few years since I started designing and selling Suncatcher Stickers. I decided it was time to set some minds at ease. I'm going to use this comment from my Instagram Comment section to kick off this blog post because I can totally see where they're coming from with the question.
Short answer: NO. Suncatcher Stickers will not cause fires.
Long answer as provided by my Very Clever Suncatcher Printer: "It’s impossible. The material actually diffuses the light and makes it cooler. The light is diffracted (split into many parts) and is not focused (which would be like a lens). There is no way that the material could suddenly magnify and heat up."
So, what is Diffraction? Time for a little science lesson.
Diffraction of light refers to the bending or spreading out of light waves as they encounter an obstacle or pass through a narrow opening.
Think of the light waves as tiny ripples in a pond. When you drop a pebble into the water, the ripples spread out in all directions, even passing through narrow gaps between rocks. Similarly, when light encounters a narrow opening, it diffracts and spreads out on the other side.
When light waves diffract, they undergo changes in their direction or interference patterns, but the energy carried by the light remains the same. The diffraction itself does not cause an increase in temperature or generate heat.
HOORAY! I hope this helps, and you can enjoy your rainbows in peace, and not worry about setting fire to your house.