Sometimes the mold of a plaster pour is just as interesting as the finished product itself. With this project, the goal is to create a wire mold in which you can insert the plaster and leave the mold there as well.

Step 1: Materials

To make the plaster, you will need

2 plastic cups
1 cup of plaster (I recommend Plaster of Paris)
1 cup of water
1 stirring stick
2 Ziploc bags (sandwhich size preferable).

To make the box frame, you will need

.05 piano wire (about 8' total)
1/8" basswood stick, 24"
X-Acto or Olfa cutter
metal cutter
tacky glue
hot glue gun + sticks
pliers are recommended.

I recommend you make a digital model to plan ahead for the pour, but I also have uploaded my own Rhino file.

plaster.3dm
Download

Step 2: Step 1: Make Digital File

In order to know where the wires must be placed, it would help to have a digital model of the shape you wish to create. I highly recommend choosing a simple geometric form, with no more than 8 faces.

Once you choose a form, extend all the tangent lines of the shape until they intersect with where the bounding box will be (1.5" x 3" x 6"). Once you do that, create lines between where the tangent lines end and the actual bounding box. If done correctly, you will have created 6 faces with lines crossing them, along with some lines crossing the box diagonally.

See sample Rhino file for reference.

Step 3: Step 2: Creating the Box

Cut the basswood stick into

4 1.5" sticks
4 2 3/4" sticks
4 5 3/4" sticks

Glue them together with tacky glue to create a 1.5" x 3" x 6" box

Step 4: Step 3: Bending the Wire

To know where to place/bend the wire, use the digital file as a reference and mark on the box. Since it is sturdier to bend wire instead of to cut and then glue it, try your best to keep the lines continuous along the same faces of the box, as shown in the image.

This is the most difficult part of the project, since piano wire can be difficult to control and accuracy counts. Do your best to keep to the form you chose, but be aware that it'd be very difficult to make it perfect.

Once one piece of wire is too difficult to work with, cut it and glue it (with hot glue) to the box.

Repeat until all the faces of the box have the wires you need.

Step 5: Step 4: Gluing the Diagonal Wires to the Box

Once you have all the wires on the bounding box, start gluing the wires to each other. These are the wires that cross the box diagonally, and the ones that will actually work as the mold for your plaster.

I used hot glue to join them together, but if you would like better craft and stronger connections, I would recommend epoxy.

Once you finish, you should have something similar to the image.

Here is when the simplicity of the shape helps the process. The simpler the shape, the less lines/wires you create.

Step 6: Step 5: Inserting the Plastic

Insert one of the ziplock bags into the wire form. It might make it easier to cut off the top of the bag so the stiffness of the top doesn't interfere with your form.

Once you loosely place the bag inside, notice where you would like to stop your pour, and cut about 1/4" above that so you don't have extra plastic in the way. Once you do this, replace the bag inside the box and make sure it is inside the form well enough to take the form of the wire. It might help to pull at the plastic using pliers, just make sure you don't make any holes!

Step 7: Step 5: Making the Plaster

Grab about a cup of plaster and pour into one of your plastic cups. Fill another cup with water, and start pouring little by little into the plaster until you get the consistency of thin pancake batter. Stir with a stick until you have a smooth consistency.

Pour plaster into one of the ziplock bags. Close the bag entirely, and then cut a small opening at one of the corners. Carefully, twist the other corner without letting plaster spill out from the cut corner until you could comfortable squeeze plaster from the bag.

Step 8: Step 7: Pour Plaster!

Very carefully, squeeze the plaster into the plastic bag inside your form. Do so carefully and slowly, and stop every now and then to tug at the plastic to make sure the plaster goes in entirely.

Once you pour it in, rest the box carefully and wait at least 20 minutes to an hour (depending on the size of the pour).

Step 9: Step 8: Take Away the Plastic

Once the plaster dries, carefully cut the plastic with a knife and pull at it from the plaster model. Make sure you don't add too much pressure to the wires (as they might fall out).

Once you take the plastic out, you're done!

Side note: if you would like a cleaner look, strengthen your wire connections with epoxy, and carefully remove the wooden sticks from the wire. The wires should be able to stand by itself!