Terms such as silicone putty, silicone mould making, press moulds and release agents will be described in this article to assist you to make simple moulds such as jewellery moulds this new easy way, using silicone putty.
Silicone putty has been used by the dental profession for many years. It has recently become a cost effective substitute for making simple press-in moulds that are suitable for use in the food industry.
It should be noted that Silicone Putty, although a dental product, has not been registered with the authorities as a food grade product.
The putty has a consistency of dough and is easy to work with. The cost effectiveness is realized because you only need the exact amount of putty to cover the surface of the object and to make a small lip around the object.
Making a Silicone Putty Mould:
Step 1:
Use equal parts of part A and part B of the putty. Mix together by kneading until the colour is consistent.
Step 2:
Using your hands, roll the putty into a ball and flatten it to about twice the thickness and width of the object to be used.
Place the object you wish to duplicate on some grease proof paper. Spray the object with a light coat of release agent such cooking oil.
Step 3:
Now commence to roll a ball of the putty over the top of the object, slowly pushing it steadily with your thumbs till the object is covered. Make a lip of about 1cm around the object with the putty to enable the mould to be held in a stable level position during the casting.
Note:The clay is pressed over the object rather than pushing the object into the putty and embedding it, as this slow action pushes the air ahead and prevents air bubbles being embedded in the mould.
Step 3:
The process time for working with silicone putty is about 3 minutes. To fully cure silicone putty takes between 20 minutes and an hour. Using heat can speed up the curing process. The object can be left in the mould overnight to ensure accurate curing.
Curing with Heat:
Once the object has been removed from the silicone putty mould curing can be expedited by using heat. To cure using heat, place the object on a sheet of tinfoil inside an oven. DO NOT use a toaster oven. Set the oven rack so that the mould is at least 15-20cm away from the heating element. Heat the mould for one hour at a temperature between 150-200º C.
Care of Food Moulds:
Food moulds made from food grade silicone putty, should only be used for foods and NEVER for any other purpose. They should be washed and cleaned after each use by using warm soapy water and left to dry. Moulds can be used in conventional ovens at temperatures up to 200ºC.
Low Temperature Alloy Metal Casting:
Low temperature melting alloy metals can be cast into silicone putty moulds as long as the temperature does not exceed 200ºC. It is important that prior to beginning a metal casting project the manufacturers MSDS sheets should be consulted to ensure that the standards of use are being met. This would include temperature, toxicity and safe handling of the materials are understood. It goes without saying that use of protective equipment should always be a priority when working with molten metals. This would include hand and eye protection as well as a heavy gauge apron.
Storage:
Store the original object in the mould by placing the two in a cool, dry location. This will help the mould to retain the original objects shape and help to prevent distortion.
Mould Making Problems:
* Mixing silicone putty has roughly a three minute time frame. Putty tends to get hotter and harder to work with if the three minute window is exceeded.
* Streaks in colour are a result of improper kneading of the silicone. Improper kneading can also lead to soft and uncured sections of the mould. Knead until the colour is consistent.
* If the mould has a rough texture it is due to improper curing. Gas within the silicone has caused air bubbles.