Introduction: How to Create Double-Casted Forms Using Rockite and Glycerin

For this experiment, I wanted to explore double-casting using Rockite and glycerin.

I'll be taking foam pieces, casting them inside of a mold using Rockite, and then casting the original shapes back into the forms with colored glycerin while using the first cast as formwork.

You will need:

  • foam core
  • cutting mat
  • straight edge
  • box cutter
  • hot glue gun
  • Rockite
  • honey-glycerin soap base
  • food coloring
  • black spray paint
  • clear matte enamel fixative spray
  • block of styrofoam
  • hot wire styrofoam cutter (optional)

The total time for the project is around 2 hours, not including curing time, and assumes a familiarity with the use of Rockite.

Step 1: Cut and Assemble Formwork

Using a cutting mat, a straightedge, and a box cutter, cut 6 individual pieces to use for the mold.

My approximate dimensions for the mold pieces were:

  • 1 x (6" x 3")
  • 2 x (6" x 2.5")
  • 2 x (2.5 x 3.5")

After adjusting the dimensions accordingly if you would like to change the size of the form, assemble the individual pieces using a hot glue gun.

Be sure to add tape to the outer seams to ensure that the no liquid will leak out during the curing process.

Step 2: Select Your Foam Pieces

Our next step is to select the pieces to use inside of the formwork.

Foam is a great option as it will be very easy to extract after the Rockite has cured. Harder materials such as wood or metal are not suitable as they will be embedded into the Rockite and would be difficult to remove.

To find interesting shapes to use inside of the mold, I sliced small pieces from a large piece of packing foam that I found inside of a TV box.

My set of rules for the foam pieces were:

  • Light should be able to travel through each created during the first cast, which for most pieces will require a flat edge to sit flush somewhere in the mold.
  • Each piece should be placed to allow for a strong, continuous form.

These rules ensure that each final piece will be unique, but that multiple pieces will work well together as a collective set.

Step 3: Pour the Rockite

Mix and pour Rockite into the formwork, and fill it to the desired height.

Place your selected foam pieces into the mold where desired, and tape them down so that they stay in place.

If you are using my size dimensions, the height of the Rockite (with the embedded foam pieces) should be 1.5".

Set aside the Rockite to cure for at least an hour.

Step 4: Remove the Formwork and Clean the Form

The next step is to remove the formwork and sand it down to give it smooth edges.

Depending on the shape of your foam pieces, this step will take some time to dig out all of the pieces and sand down the rough edges.

Step 5: Color the Block

The next step is to apply color to the Rockite block. I would consider this step to be optional as it covers the interesting textures of the Rockite, but gives it a nice smooth finish that might be preferred. If applying color, a dark color will work best as it will contrast well with the glycerin. I chose to color the block with black spray paint, and applied a clear matte enamel finish to protect the outside and give it a clean look.

Step 6: Pour the Glycerin

The next step is to create a new mold and pour the glycerin. After melting the glycerin, I added blue food coloring to it to give it a nice color. Pour to Glycerin into the voids and set aside to cast.

Step 7: Remove Formwork and Clean

The last step is to remove the formwork and clean the final form. Rough edges can be shaped easily using a wet paper towel. If desired, use a matte fixative to improve the durability of the final product.

Comments

author
rafununu (author)2017-01-19

Don't you need a hardener ? Glycerin is liquid at ~40°C and gel under.

author
BillyB126 (author)rafununu2017-01-20

Nope! I used a soap-making version of Glycerin that stays solid at room temperature!

author
studleylee (author)2017-01-18

I've not seen solid glycerin. Where do you get it?

author
studleylee (author)studleylee2017-01-18

Soap?

author
BillyB126 (author)studleylee2017-01-20

Yes I believe that it is a soap-making version of Glycerin! I apologize for not having specifics as I didn't save the packaging

author
BillyB126 (author)studleylee2017-01-19

l purchased a large tub for $10 at Michael's!

author
studleylee (author)BillyB1262017-01-19

Thanks. Useful to know!

author
Swansong (author)2017-01-18

This looks neat :) I'd add some lights to make it glow.

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