The grouting process posed some challenges for us, and we want to share all that here because what we learned as a result we find to be very useful for future projects.

Please note that you should really be using rubber gloves or some other form of protection for your skin when working with grout.

We used some unsanded grout we had from a previous project. We didn't want to use white grout because that would require more cleaning and scrubbing, and scrubbing is something we really don't want to have to do because the exposed surface of the CDs is plastic, and if that surface has significant scratches it will fade the effect of the holographic film when light shines on it.

After mixing the grout, we wet the surface and then applied the grout making sure to get it in all the cracks. The instructions for our grout said to let it dry for 30 minutes before taking the excess off. After more than 30 minutes, we went to take the excess off and it really felt like it wasn't dry enough yet, it was coming out from between the cracks and exposing the wall surface we started with. The CDs don't have too much depth, so there's really just a bit of grout that goes in between the cracks. I think this also happened because we left too much space between pieces, so when trying to clean the excess off, the sponge had enough space to get in between the CD pieces to take out the grout (which we don't want because we need the grout to dry between the pieces to keep them together) We let it dry for a while longer and when we tried again it seemed to be doing the same thing (we definitely left too much space between the pieces). At this point, late in the night and frustrated by the thought that maybe this wouldn't work out and our dream of a shiny backsplash was being shattered, we reapplied more grout and left it overnight. ERROR! In the morning, the grout was REALLY REALLY dry. YAY! Right? No. When I went to clean it off with a wet sponge, it required way more muscle to take off than one should ever need for the task. But hey, hope was restored, so I was willing to put in that work to see it finished. I spent a couple of intense hours cleaning the dry grout with water and a hand towel - during this process I realized that the surface of the CDs was being scratched by the movement of the grout as I was cleaning it away, but there was not other option at this point. Once everything was cleaned away, I did a final wipe with vinegar water to take off any fine powder left on the surface.

In conclusion, if we had left less space between the pieces, we wouldn't have had the problem of the grout coming out when we tried to clean off the excess. The grout has a specific time for drying and if it is left longer it will become hard to take off. Because we let it get hard, cleaning it off was difficult and that scratched the pieces in the process. The scratching of the CDs did indeed fade the colors a little bit and made them a little less intense when light shines on them, but that really doesn't take the magic away.