Don't worry too much about this problem, such as professional production sites, KT boards, adhesive-backed photographic paper, etc. , can no longer be used. If you want to keep it longer, just put it in a place with similar temperature, as long as the humidity is not too high. As long as it is not exposed to the sun, it will be the same after a while. Under normal circumstances, it is impossible for the Louvre to preserve the Mona Lisa. Just keep it carefully. These things are not expensive either (of course, being killed by a painting company is not necessarily cheap). It really doesn't look good after a few years. You can draw another picture, or design a better picture with the baby's family of three.