Body Casting Tutorial: Hydrogel Mold & Cold Cast Bronze Casting

Body molds and castings can be made using a variety of products. The following tutorial details the steps needed to create a Hydrogel® body mold and a cold cast bronze body casting.

 

Step One: Apply Hydrogel® to Model

Position the model (the ropes, pictured in Figure 1, allow the model to hold her arms in that position more comfortably) and carefully apply Hydrogel® Mold Compound.

Hydrogel is a white powder that, after mixing with water, cures in approximately five minutes to a moist, rubbery material. Hydrogel is skin-safe and is useful for making quick, single-use molds. A variety of casting materials, like plaster, wax, and some polyurethane resins, can be poured directly into Hydrogel molds.

 

Hydrogel Mold Compound Polytek

 

Apply the first layer of Hydrogel very carefully to avoid entrapment of air. After application and cure of the first layer, apply a mixture of baking soda, water, and food coloring [Figure 1]. Food coloring helps to ensure thorough coverage against the white hydrogel, while the baking soda and water help to adhere the second layer of Hydrogel to the first layer.

 

Hydrogel Body Mold

Figure 1

 

Apply the second layer of Hydrogel. Overall, the thickness of the mold should be approximately 1/4″.

Add cotton batting to the second layer of Hydrogel [Figure 2 & 3] so that the plaster mold shell (constructed in Step Two) will have fibers to adhere to. When the second layer of Hydrogel cures (~5 minutes), remove excess cotton and prepare the plaster.

 

Body Mold Hydrogel - Cotton Batting

Figure 2

Hydrogel Body Mold - Preparing for Plaster Shell

Figure 3

 

Step Two: Make Plaster Mold Shell

Create a hard outer shell to support the soft Hydrogel mold.

Carefully apply plaster bandages over the Hydrogel (another option might be the use of plaster and burlap) [Figure 4].

 

Body Casting - Plaster Mold Shell

Figure 4

 

Step Three: Make a Plaster Casting

When the plaster mold shell has cured (the total mold making process took us approximately one hour), carefully remove it from the model [Figure 5].

 

Life Casting Mold

Figure 5

 

Immediately pour plaster into the Hydrogel mold; this needs to be done right away as Hydrogel molds dry out very quickly and become unusable.

When the plaster has cured, remove it from the Hydrogel mold [Figure 6] and retouch the casting as necessary (at this point, the Hydrogel mold is no longer needed).

 

Body Mold and Plaster Casting

Figure 6

 

Step Four: Make a Rubber Mold of the Plaster Casting

After retouching the plaster casting, a long-lasting rubber mold can be made.

We chose to use Polygel® 40, a self-thickening polyurethane rubber, to create this mold (NOTE: Polygel® 40 is no longer available – Polygel® 35 has taken its place). Polygel 35 has a mix ratio of 1A:1B, a working time of 8-10 minutes, and demold time of 8-12 hours.

Apply a relatively thin first layer of rubber in order to pick up detail and avoid air bubble entrapment [Figure 7].

 

Brush On Mold Body Casting

Figure 7

 

Apply layers of rubber until a mold thickness of at least 1/4″ is reached [Figure 8]. Always allow the previous layer of rubber to gel before applying the next one.

 

Polygel Brush On Rubber

Figure 8

 

If necessary, add PolyFiber II (a thickening agent) to Polygel to create a thicker rubber for filling undercuts on the casting.

 

Rubber Body Mold

 Figure 9

 

Allow the rubber to fully cure before moving on to the next step.

 

Step Five: Make a Two-Part Plastic Mold Shell

Construct a shim (cardboard and duct tape are used here) and registration marks (clay and rubber are used here) to align the two halves of the mold shell [Figure 10]. Apply a sealer (e.g., paste wax) to the cardboard shim to avoid bonding of the plastic. Also apply a release agent (e.g., Pol-Ease 2300 Release Agent) to the shim, rubber and clay to avoid bonding.

 

Shim for Two-Part Shell
Figure 10

 

Mold Shell Material: Combine Poly 1512X polyurethane plastic and Poly Fiber II (a thickening agent) to create a plastic with a brushable consistency [watch a video tutorial of creating a mold shell here: http://youtu.be/3sVc2U_-LNM].

Brush-on one half of the mold shell (to where it meets the shim) and allow it to cure (approximately 30 minutes).

NOTE: Cured plastic can have very sharp edges, so consider sanding down the edges before handling the mold shell.

Remove the cardboard shim, apply a release agent to the exposed cured plastic and rubber and then brush on the second half of the mold shell and allow it to cure. [Figure 11].

 

Two Part Plastic Mold Shell

Figure 11

 

When the mold shell is completely cured, drill holes through the parting line so hardware [e.g., nuts and bolts) can be inserted in order to secure the two pieces together for casting [Figure 12].

 

SecureMoldShell

Figure 12

 

Step Six : Cold Cast Bronze

The mold is now ready for casting. To create a cast bronze effect, use a combination of EasyFlo 60 polyurethane resin, Bronze Powder, and PolyColor Brown Dye [Figure 13]. EasyFlo 60 has a mix ratio of 1A:1B, a short working time of 2-2.5 minutes, and a demold time of 15-30 minutes.

 

Cold Cast Bronze Kit

Figure 13

 

Spray and brush out Pol-Ease® 2300 Release Agent onto the mold before pouring the resin mixture.

 

Rubber Mold Life Casting

 

Use the following volume ratio to create the cold cast resin:

By Volume:

1 Part EasyFlo 60 Part A

1 Part EasyFlo 60 Part B

2 Parts Bronze Powder

 

Thoroughly mix the resin and brush it into the Polygel® mold. Because of EasyFlo 60’s short working time, it is important to work relatively quickly.

 

Cold Cast Bronze Slush Cast

Brush On Cold Cast Bronze

Bronze Resin Casting

 

After allowing the mixture to cure for approximately 15-30 minutes, apply another layer of EasyFlo 60 plastic and PolyColor Brown Dye as supportive backing (we did not use bronze powder in this layer).

 

The Final Cold Cast Bronze Body Casting

When the resin is completely cured, remove it from the mold and hand burnish it with steel wool to expose the metal particles. Additionally, a patina can be applied (not pictured here).

 

Cold Cast Bronze Body Casting

 

Video Tutorial

Watch this video tutorial to see Hydrogel® being used to make a hand mold:

 

 

 

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