Casting Techniques: Part 2

Earlier I mentioned a few ways of unconventionally making molds and casts in Casting Techniques: Part One (CT1). It went over how deciding which casting techniques are best for certain projects and why. Now we’ll get to the fun stuff – creating.

Casting and Replicas with Hot Glue

Items you’ll need:

A hot glue cast of river rock.

An object you’d like to recreate

Heavy duty aluminum foil

A hot glue gun (check CT1 if unsure which size to use)

Bag of glue sticks

1)      Heat up your glue gun. Make sure to have it standing on something to protect  surfaces from drips or burns.

2)      Rip a sheet of foil large enough to cover three-fourths of your object. Remember if you are using an object that has creases, indents or other features, you will need to press the foil tightly into those elements to have them show up on your mold.

3)      Start spreading glue over foil, using the nozzle of the gun to help guide and spread the glue covering the foil. Pay special attention to the ridges or indent features, making sure to get in every cranny. TIP: Hot glue sections at a time, let cool and go back to glue another section. This will help prevent burns.

4)      Once the foil surface is covered in glue, let it thoroughly cool. Pull the flexible mold off of the object. Check for any holes and apply glue to those spots and cool.

5)      With the completed mold, you can paint it and use it as a light-weight replica, or you could use it to cast multiple replicas in plaster or other casting materials.

Using Plaster of Paris of Paris

Plaster river rocks made from hot glue molds are arranged on a frame for a well prop.

Plaster is great for casting and sculpting objects. It holds up well in the elements and can be painted quite easily. If you don’t have any leftover plaster from a previous drywall patch-up, you’ll find it at your local craft, hardware or superstore.

The plaster powder usually comes with instructions on the ratio to water mix.  Depending upon your time restraints and the thickness of the object, you may want to change the ratio.

The ratio can be changed by adding more powder to shorten the drying time, but keep in mind, the thicker the mix, the faster you’ll need to work on pouring. If it’s too thick, it might not get into all the grooves of the mold.

Brittleness can be an issue if your object has thin edges. Adding fibers such as gauze or paper sometimes reduces this problem.

Liquid Latex or other chemical hardeners can be added to plaster, but the cost jumps up significantly without the significant benefit. If you drop or hit any piece of plaster hard enough, it’s going to break, with or without additives.

CAUTION:  Do not try to cast your hand or other body parts in Plaster of Paris. It heats up and can cause severe burns. Follow the package directions for more information.

John Britt Pottery shows how quickly you can mix plaster and make a 2-piece mold in this video:

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  1. Pingback: The Well from the Movie The Ring | Frugal Frights and Delights

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