Instructables
This is a little cast concrete pendant I made for my lovely girlfriends' birthday a little while back, paired it with hammered copper bracelet and a fancy little display stand.  

This whole project takes roughly 2 or so hours from start to finish, and the results are great, she has gotten a ton of compliments on the piece, and it only cost me about $3 worth of materials.
 
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Step 1: Tools and Materials

To make this concrete pendant, there are a few materials and tools that you will need to gather before you can begin.  

Materials
  • Plywood or solid wood-  2 pieces cut to the same size, these are going to end up being the form we cast the concrete in, mine were approx 4 1/2" x 6"
  • small piece of solid strand copper wire, I used the ground wire out of a small piece of 12-2 romex about 2" long
  • Kreg pocket screws or really any 1 1/4 screw ( I like the Kreg ones because they are self drilling and washer head)
  • Hydraulic cement
  • Mixing cups and a stirring implement-  I used a couple of small solo cups and a plastic spoon
  • Finish- concrete sealer or a lacquer
Tools
  • Router Table
  • Router
  • Core Box Bit- I used a 5/16
  • Dowel- same size at the core box bit, mine was a 5/16 again
  • Drill/Driver
  • Clamp
  • File
  • 220 and 400 grit sandpaper
Duplicity1 year ago
I have not made a necklace, but have made concrete weights before. An easier trick I have used has been pieces of copper water pipe or pieces of plastic PVC pipe. If you seal one end and lightly spray with silicone spray to act as a mold release you can just pour the concrete in, add you wire loop and when it hardens just tap it out from the bottom. You would then clean up if you were going to lacquer but the silicon spray actually leaves a really cool and durable finish. With something like pipe, it is super smooth when you pop it out. No sanding required.
jbeaton (author)  Duplicity1 year ago
thanks for the idea, sounds like that would work out pretty nicely. For this one i wanted the rounded bottom just for aesthetics, but to get a cleaner cylindrical look that would definitely work. I think I may give that a try the next time I am doing some casting. Thanks for taking the time to read through and post!

Using Duplicity's method, you can always shape the end of the cylinder after demolding to get the rounded end that you want.

Battlespeed9 months ago

Is it really completely cured enough to seal it that soon? Seems like you'd want this to set for a day at least before sealing it.

artworker1 year ago
How much does it weigh? Just asking as I am planning to make something complex and little larger than this.
jbeaton (author)  artworker1 year ago
just threw it on the scale and it weighs 22g or about .8oz. not very heavy at all
Cool! thx!