How to Buy Silicone Rubber
When deciding to buy silicone rubber to make chocolate molds, there are a few factors that you need to consider. First and foremost, you must make sure that the silicone you buy is food grade, or suitable for contact with food. Next, there are varying properties or characteristics that a silicone product will have, and you will want to make sure you buy a product that works best for your particular project. Some of the things you should consider are:
Working Time: The amount of time you have to work with the silicone before it starts to cure. You need to consider the amount of time you will need to mix the two part silicone mixture, degass it, if needed, and slowly pour it into the mold. This time can run from a matter of a few minutes to a few hours, depending on the product.
De-Mold Time: The amount of time it will take for the silicone to fully harden to the point where you can remove the model and test the mold. This can range from a few hours to a day. There are additives that can be purchased to speed up the de-mold time.
To View eBay Products you must right click to open in a New Window
Durometer: The hardness of the silicone rubber in its cured state. The hardness scale used for silicone primarily is the Shore A scale. The lower the number, the softer the rubber. You will choose a particular durometer based on the type of model you will be molding. The more detailed your model, or the deeper the undercuts, the softer you will want the silicone. An undercut is a cut, or groove.
Mix Ratio: This will tell you how to measure the two parts of the silicone mixture. Some silicones must be measured by weight. If you do not have the proper scales, you will want to find a silicone that can be easily mixed by volume.
RTV: This stands for Room Temperature Vulcanizing, which means the silicone rubber will cure at room temperature. Some silicones, particularly platinum based silicones, need to be cured with heat. If you buy a RTV silicone, you can just let it sit out until it hardens.
Thixotropic: A thicker type of rubber that can be brushed on. Brush on rubber is useful for making molds of large pieces or for items that cannot be moved.
Storage Information: Pay attention to how long the silicone is good for and what storage conditions must be maintained. Some silicones are only good for a few months and must not be kept in hot or humid areas.
Again, the type of silicone you buy will depend on your particular needs. Check with the manufacturer or distributor of the silicone for the properties before you make any purchase.