This is an Instructable for making a custom chocolate bar based on engraved material using food-grade silicone (casts can be made of gummies or hard candy as well).

The idea was a gift for my niece who is addicted to chocolate. It was a great way to teach her about mold-making & casting, as well as sharing! (we made party favors)

You will need:

Materials
- Acrylic, size to your specifications
- Equinox Silicone Putty (I used Equinox 38)
- Chocolate
- (Optional) Hot Glue

Tools
- Access to laser cutter
- 2 pots
- Stove Top
- Refrigerator
- (Optional) Hot Glue Gun

Step 1: Design and Make Your Engraving

I designed a simple illustration in Adobe Illustrator, saved it in SVG format, and then used a laser cutter to etch the image into a 3"x2", 1/4" thick piece of acrylic. Be sure to wash the piece with cold water to remove dust particles prior to next step.

Alternatively you could use wood. I like acrylic because it is clean after being etched and doesn't need any additional modifications such as sealing. Also, I would NOT recommend using masonite or similar material that can be cut with a laser if particles might find their way into your mold.

If you are interested casting multiple piece at once, I recommend designing a gang mold at this stage.

Obviously this form is modeled after a Hershey's bar. If you are interested in making a grid of pieces that can be broken up, design your illustration for the form accordingly.

Step 2: Make the Mold

Equinox silicone putty is a unique product that can be directly pressed into a form. It is a food-grade silicone that can be used to make a range of edible products. It is also great for teaching children about mold-making because the product is non-toxic and very hands-on.

(Optional but Recommended) Hot Glue your form onto a clean surface. This will prevent the form from moving when you are making the mold.

(1) The process is extremely simple - grab two chunks of equal size and roll them into balls. Mix part B (the purple-colored material) first, and then incorporate part A (white material). Mix until homogenous.

(2) Press material onto the form. In order to get maximum detail, you'll want to make sure your "wall" is not too thick on-top and around the material. This may take a bit of practice & experimentation. See images for potential artifacts / defects.

(3) When form fully cures, wash with soap and warm water for 5 minutes. (for those familiar with mold-making, post-cure is NOT necessary for this product).

Safety Note: Keep in mind that the Material Safety Data Sheet (MDMS) recommends goggles and gloves, but technicians have advised me that this is not necessary as there are no hazardous materials found in the product, also explained in the data sheet. That being said, it may be wise to use safety gear if using this material with a group, as young children may swallow the material, throw it at each other, pick their nose, or rub their eyes before washing their hands. My niece is 4 and we were fine without goggles and gloves, but she was under my constant supervision. I chose this material as opposed to another type of pourable silicone BECAUSE it is safe to use with bare hands, as long as it doesn't find its way into one's eyes or mouth.

Another important note: when selecting your product, you should be familiar with technical terms such as "pot life" and "de-mold time" as Equinox comes in three different varieties. Pot life is the working time of the material and de-mold time is the duration until full-cure. I recommend using either Equinox 38 or 40 because the pot life is 4 minutes and 30 minutes respectively. Equinox 35 has a pot life of 1 minute, so it becomes hard EXTREMELY fast and is not recommended for use with children because it will begin to cure before the material can be fully mixed. I used Equinox 38 with my niece and it cured a little too quick for her, which resulted in artifacts in her first molds. For an adult, 4 minutes is enough time, provided your object is small.

Step 3: Melt Chocolate, Pour Mold, and Freeze

A technique for melting chocolate without burning is to use a double-boiler. If you don't have a double-boiler, you can simply put one pot on top of another.

(1) Boil water

(2) Put chocolate in second pot on top of pot with boiling water

(3) Scoop / pour chocolate into mold

(4) In order to ensure air bubbles are not present in surface, grab sides of mold and tap onto surface gently. This is a common technique used for pouring plaster, as well as concrete.

(5) Put into freezer for at least 1/2 hour.

I hope you enjoy this instructable, and if you decide to pursue a commercial application with this material, be sure to adhere to FDA standards for packaging food. For small scale gifts such as party favors, I found that wax paper is a good material for protecting the chocolate bars.