There's a sort of predictability and assurance to the process of making these lampshades that combines nicely with the infinite creative possibilities that are possible using varying amounts of the two ingredients (epoxy and concrete) that appeals to me. That, and the fact that I was looking for a way to make several similar lamps for a rather industrial-looking space I'm working on, made this the perfect project to tackle. Once I made one it felt like I could effortlessly manage making a new one daily.
concrete lampshade mold
FastSet All-Crete High Performance Cement Mix (20 lbs.)
Crystal Clear Table Top Epoxy (2 quarts)
powder pigment for resin/epoxy
A word about supplies: I included the exact products I used to make the lampshades, but you could probably use just about any type of cement mix (or even pre-mixed concrete) and probably even any two-part epoxy/resin and certainly any resin powders to make these. Also, once you've made one you'll see that the mold is designed to use very little of the two (epoxy and cement), so a little goes quite far. With the materials I suggested and the mold I purchased (it's approximately six inches high and five inches in diameter) I could probably have made about seven to ten lampshades with that amount of supplies. If you like the part of the lamp that's build with resin (the translucent part) more than the concrete, purchase more of that--perhaps half gallon containers rather than quarts.
When the lampshades are finished I recommend getting the electrical parts from the Color Cord Company. https://www.colorcord.com/
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Mixing and Pouring the Epoxy
When I first put my mold together I could not believe the epoxy wasn't going to spill out of it since the place where the mold comes apart is near the bottom, but with the mold firmly together the epoxy doesn't even slightly spill out. Still, I put my mold together and put it on a sturdy disposable platform on top of the table just to be safe. Once you have the mold together, it's time to mix the epoxy--the translucent bottom layer of the lampshade.
Because my cups didn't have measurements on them, I put marks on them first by simply measuring out the amount of each part of epoxy I wanted to use with a water substitution and marked the cup at the top of each measurement. (This is just to ensure I use equal parts of part A and B; you wouldn't want to guess and I'm even hesitant to estimate by looking at the bottles.) I began with 25 ml. of both parts. If you want the light to simply be diffused (through the epoxy part of the lamp shade) and don't want to add color to this area, just mix equal parts of the epoxy--the resin and the hardener--in a disposable cup. If you want to add some color, put a small amount of the powder into the mix as you stir it around. Obviously the sooner you add the powder, the more it'll be evenly mixed in. Sometimes I wanted a more marbled look, so I added it later in the stirring. Either way, you'll want to mix the two-part epoxy very well so that it hardens evenly. I usually mix quite rapidly for at least a full minute. Consider, too, that the bubbles in epoxy sometimes do show up in the final piece. If you want to get the bubbles out, you can use hot air (either from you own lungs or a hair dryer) to make them rise to the surface. I tend to embrace the bubbles because I like the way they look and because there's a limited amount of time you'll have before the epoxy thickens.
Once you've got the epoxy mixed and stirred, pour it into the mold. (Where you pour the epoxy into the mold can make a difference in the overall look of the lampshade, but you'll establish what you like as time goes on.)
Step 2: Waiting
While it may seem ridiculous to add a step for wait-time, it feels like a step in the process because it's kinda long. If you want to have some bizarre mixing going on between the concrete and the epoxy you could probably pour almost immediately, but I've found that waiting at least an hour is really important if you want a pretty firm separation between the two. For best results I actually wait at least two hours before I put the concrete mix on top of the thickened epoxy.
Step 3: Adding Concrete
This is the easy part. I had no idea that mixing concrete was so simple. In fact, I keep waiting for something to break because it seems like it's too easy? For a project like this, when you're not trying to hold up a bridge or something like that, you can really mix the concrete to be a certain consistency rather than measuring--or at least that's what I've found. I tend to mix just a little too much just in case and because I generally have more concrete mix than I need. Pour about 200-300 ml. of the concrete powder mix into a mixing container and then slowly stir in cold water. Stop when the consistency is thick and pasty, but pourable. This mix sets fast, so as soon as it feels like it's all stirred up, pour it right into the mold. If for some reason you didn't make enough, don't fret; just mix more and pour it on top of that. You'll probably end up with a subtle, but lovely line where you made the second pour.
Step 4: Waiting Longer
This wait is a longer one because the entire lampshade needs to settle and take shape. I've actually never taken the mold off too soon, actually, so I'm not sure what too soon is, but I know that the soonest I've taken the mold apart is within about 12 hours of when I finished pouring the concrete.
Step 5: Removing the Mold
Once you've waiting as long as you think you should wait--my recommendation being at least 12 hours--you can wiggle the mold off. Sometimes I've found that having a second person to pull the bottom off helps because the motion is done more evenly. If you think parts of the mold are getting sticky you can apply a thin layer of silicone spray so that the epoxy and concrete don't stick to that area as much. Still, I've found that the silicone mold only has a life that's so long. I made about 10 lampshades with my first mold and 20 with my second one before it started sticking too much to use again and get the lampshade out of the mold.
Step 6: Adding Electricity
I won't go into detail about adding electrical components to this project, but if you order the products from Color Cord or any other electrical supply I think this part is pretty straight forward. The silicone molds are made with standard elements in mind, so my experience is that they came fitting perfectly.
Participated in the
Stone Concrete and Cement Contest