I'm not sure between the caulking and hot glue which one sticks better. I thought the caulking was working fine, but several caps have had to be re-glued. I had used a caulking gun to squirt it out on cardboard and the students dipped the caps and stuck them down. I think some students just didn't get enough caulking on the back, while others got WAAAAAY too much. The maintenance crew that hung the panels suggested Spikes Special Adhesive and left me a small tube for repairs. It does seem to be sticking really well and is definitely stronger than the caulking. However, I don't know how the cost would compare. I suppose it's another option for someone to look into.
Overall, I was pleased with how things came together. In previous years, I've let the students totally design the panels. This year since I knew they would be permanent, I gave students the option of submitting plans and I had things sketched out before they came. The outer space panel was based on a student's sketch and I designed the READ mural for the library.
Students working on painting and applying caps to the space mural.
The space mural turned out pretty good, but has weird gaps. Students said we were out of black caps (found out later they just didn't look carefully enough) so we spaced the caps out. Now there are gaps just a tiny bit too small for me to fill them in. I hung up signs on either side reminding students not to touch but it's a high traffic area so I'm sure it will happen. One of the custodians is talking about using some small screws to secure more caps.