Using 3D Chocolate Molds
For Solid Plaster Casting
By Bob Sherman
Chocolate molds are well suited to plaster crafting and they are very inexpensive. This article will explain how to use 3D chocolate molds for making solid plaster castings. 3D molds are sometimes referred to as assembly molds because they have two or more parts that need top be clamped together.
Important - This method works well for pieces up to approximately 4 inches in diameter - sizes larger than that should be hollow molded which will be discussed in a future article. Use of this method on larger molds may damage the mold because of the heat generated as the plaster cures.
PLEASE NOTE!! - Plaster crafting is fairly safe if you observe these safety rules when mixing plaster. Once hardened there is little or no hazard from handling plaster items:
- Plaster is very alkaline and and exposure to high dust levels may irritate the skin, eyes, nose, throat, or upper respiratory tract. Wear a dust mask, eye protection, and rubber gloves when mixing plaster.
- Do not wear contact lenses when working with plaster.
- Plaster generates a lot of heat when setting - never use plaster to make casts of body parts.
- Keep away from children or pets.
- Other safety precautions may apply depending on the plaster product you use - read the directions.
Plaster is used throughout this article to describe casting products containing mostly plaster of paris. The two most common are plaster and hydrocal. Either type will work for this.
- Plaster is generally 100% plaster of paris and is called a variety of names depending on the manufacturer. These include: Plaster Of Paris, Casting Plaster, or just plain Plaster.
- Hydrocal is a mixture of plaster of paris and portland cement and is called a variety of names depending on the manufacturer. These include Hydrocal, Hydrostone, and Ultracal. Typically hydrocals are 3 times stronger than plaster and more dimensionally stable. For castings with thin areas hydrocals are a good choice.
Plaster Casting Supplies
The following plaster craft supplies will be needed to follow along with this article. Clicking on the item name will bring you to that item's page with a full description and ordering information.
Please Note: We are discontinuing plaster crafting products but have left these instructions up as a public service.The links below may may be non functional by the time you read this.
|Chocolate Mold||A 3D chocolate mold is needed. A Happy Bunny Mold was used here.|
|Mold Clips||Needed to hold the mold halves together. For a mold this size two packages are needed. If you prefer, binder clips from the stationery store may be used.|
|Mixing Bowl||A flexible mixing bowl simplifies cleanup, but you may use any plastic bowl.|
|Plaster Blender||This requires a power drill to use, but makes blending the plaster much easier. If you don't have a power drill, a potato masher may be used to mix the plaster manually. For very small batches you could even use a stick.|
|Airid||Optional, but recommended. This will help eliminate air bubbles in your castings.|
|Plaster or Hydrocal||Plaster was used here. We sell these to accommodate our customers, but you may wish to source it locally since the shipping cost is high due to the weight. Plaster may be found in most home centers and hardware stores. Hydrocal is much harder to find locally.|
|Scale||Optional. Plaster can be mixed by guesswork, but a scale will allow good repeatable results every time.|
|Mold Prop||Something to hold the mold upright. I normally use an appropriately sized box.|
|Knife||I use a standard utility knife but any semi sharp knife will suffice.|
|Toothpicks||To support hangers if necessary.|
Step By Step Instructions
|1. Use a scissors to trim away the mold sheet leaving 1/2inch of sheet around the mold cavity.||2. Use a sharp knife to carefully cut an opening on the bottom of one half of the mold.|
|3. Visually align the two halves and clamp together.||4. Fill the mold with cold water and pour it into your mixing bowl. Add a couple extra ounces. If you are using a scale, calculate how much plaster is needed for that much water. Always use cold water because warm water speeds the hardening process.|
|5. The plaster is sprinkled into the water slowly. If you are not using a scale, continue until you have a mound approximately one inch higher than the water. Let it sit undisturbed for a few moments to allow the plaster to absorb the water.||6. Mix until smooth. It is important not to over mix as that will cause the plaster to harden faster which may make it start to set in the bowl.|
|7. Fill the mold and allow it to harden.||8. When it becomes warm to the touch, it may be de molded.|
Continue To Page 2
Disclaimer: The information presented here is accurate to the best of my knowledge and common plaster crafting practices as of the time of this writing. Originally published in March 2007 and modified in April 2012. The author and the publisher accept no liability for the use or misuse of any of the information presented in this article. This article is presented for informational purposes and is used at your own risk.
Author: Bob Sherman
Publisher: Bobby's Craft Boutique Inc.
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