Silicone Putty

What is Silicone Putty?

It is a two-part RTV silicone rubber, non-toxic material with the viscosity of putty for making simple but detailed moulds. The mould will withstand temperatures up to 315°C.

This rubber does not require moulds or containers which liquid silicon or our RTV rubber requires. You simply mix equal parts of Part A and an equal quantity of Part B which requires less time and skill in preparing the rubber ready for application.

Simply put, it is the fastest, easiest means of producing a reusable mould that is flexible and accurate.

Safety Precautions

It is safe to use and does not give off any toxic fumes. Those who are allergic to silicone should still take all the necessary safety precautions. For most people however there is no need for gloves.

Silicone putty comes in two forms. A general purpose putty and one that is manufactured with food safety in mind that may be used in the manufacture of chocolates and other food materials.

Recommended Storage

Keep in a cool dark storage place with the lids firmly closed. If the putty is not exposed to air it will last for more than one year.


Part A and Part B of the silicone putty is coloured differently to enable you to ensure even and proper mixing. Don’t worry about weighing each part. Just estimate as closely as possible an equal size ball of each part. Knead them together with your fingers until the colour becomes uniform and without streaks. It is advisable to take only a minute or less to do this as the silicone starts curing soon after mixing.

How to use Silicone Putty

Once you have mixed the silicone putty press it over and around the object to create the impression. Let is set for 5 to 10 minutes. When pressing the putty over the model start by pressing from the centre of the object and moving outwards to ensure no air is trapped in the impression.

Silicone putty easily traps air as its viscosity doesn’t allow bubbles to rise as it does with liquid silicones so be careful.

A mould release is unnecessary as silicone does not stick to other objects, however one difficulty is that it can become entrapped in wood fibres and become difficult to remove. If the putty is pushed against a vertical surface it may fall away if not supported due to the easy release properties of the putty.

Unlike a mould made from a liquid silicone you will not finish with a level base to facilitate casting. One way to get around this is to attach two wooden strips to the bottom side of the putty which will act as legs on the mould.

Once the silicone putty has set it will allow you to rest the mould on these strips making a level mould to cast.

As silicone putty begins to set up in as little as three minutes after you have finished kneading, you must work quickly. Extend the putty out to at least 1 cm on all sides of the object to provide a level surface around the mould opening.

As silicone will stick to silicone any thin areas can be repaired by adding additional putty to the completed mould.

What can the moulds be used for?

Silicone Putty moulds can be used at high temperatures such as that of an oven. Therefore Polymer clays can be hardened in the moulds. All types of resin can be used as well as plasters. Chocolates and sweets can be formed in the food safe silicone putty moulds.

By Stan Alderson