Cast Candle with Alginate

Introduction

Make a cast candle from a clay model or other positive. Make a single use block mold with alginate. Everything is very messy, but quite safe.

Tools

  • Melting pot or double boiler for wax (not to be used again with food)
  • Mixing cups and stirring sticks
  • Sculpting tools

Parts

  • Clay or plasticene
  • Alginate powder
  • Candle wax (a mix of beeswax and paraffin works especially well)
  • Candle wick

Step 1: Intro

  • Make a 1-piece block mold of a clay model or other small object
  • Pour wax into it to make a candle
  • This activity takes about 30 minutes start to finish, including waiting for the materials to harden
  • Wax is hot and can burn you
  • Moldmaking is messy and can damage your clothes – cleaning tips at the end

Step 2: Make a Model

  • Use a lime to lemon sized lump of clay
  • Or use an existing physical object
  • It should fit in the small cup (12oz) with 1 cm – 3/8″ on each side
  • Make up a crazier shape than this one!

Step 3: Design Guidelines

  • The shapes shown on this step would be more challenging, especially if you take them even more extreme than these
  • Very thin walls can be more challenging
  • Lots of holes can be challenging
  • Thin wires can be challenging
  • Think about how wax and mold compound will flow into the shape. Areas that trap bubbles are tricky
  • These guidelines are made to be broken – experiment and see what you can get away with

Step 4: Mount Model

  • Stick the model to the bottom of a small (12 oz) cup
  • A thin circle of clay on the bottom can make it easier to stick down
  • Either the top or the bottom of the model at this point can become the top of the candle

Step 5: Mix Alginate

  • Mix 8 oz water with 8 oz alginate powder (1:1 by volume)
  • Add the water to a big cup
  • While stirring sprinkle the powder into the water
  • Stir vigorously for 30-60 seconds
  • It’s ok if there are still small lumps

Step 6: Pour Mold

  • Pour the alginate over your model in the small cup
  • Tilting the cup may help release air bubbles
  • Tap the cup firmly on the table after pouring to release air bubbles
  • Pour at least 1cm – 3/8″ above the top of your model

Step 7: Wait

  • Alginate takes about 8 minutes to set up
  • Unmold when it is no longer liquid, it will be firm, but jiggly, like jello

Step 8: Unmold

  • Get the mold out of the cup
    • Run a wood knife around the edge of the cup to release vacuum
    • Turn the cup upside down, press on the bottom, tap firmly on the table several times to get the mold out
    • If all else fails, you can cut the cup open
  • Remove the clay model from the mold
    • Pull it out. The alginate is rubbery, but won’t stretch very far
    • If necessary, use the wood knife to cut down the side of the mold to extract the model
    • Use the minimum practical amount of cutting to get the model out

Step 9: Prepare for Wax

  • If necessary, use masking tape to tape the mold closed. It won’t stick, but you can do a complete circle to hold everything together
  • Push a wick through the bottom of the mold. This can become the top of your candle. Pull the wick through until it is flush with the bottom surface of the alginate (where it was touching the cup)
  • Use a metal wick holder to keep the wick centered
  • Try multiple wicks if you want to get wild

Step 10: Pour Wax

  • Wax is hot and can burn you
  • Fill a ladle 1/2 full and pour wax into your mold
  • Continue filling until it is at the top
  • The wax we are using is half paraffin (to lower cost) and half beeswax (to smell great, reduce shrinkage, and refine the microstructure)

Step 11: Wait Again

  • Wait until the wax is mostly solid
  • If you notice a shrinkage hole in your candle, you can fill it with more wax
  • Once it’s solid enough, carefully remove the metal wick holder
  • Once you’ve removed the wick holder, and the wax is solid enough to not spill, you can take it with you and unmold later

Step 12: Unmold Candle

  • Once it has cooled to room temperature, tear off the alginate
  • Cut the wick off the bottom of your candle

Step 13: Cleaning Tips

  • All of the materials in this activity are safe enough to eat, but very messy
  • If you get alginate on your clothes, let it set up, and then let it dry out. It should mostly flake off, and the remaining powder comes off in the wash. Don’t try to scrub it while it’s wet
  • If you get wax on your clothes, first try freezing them and peeling off the wax. Then check the internet for advice, it isn’t easy.