Will New Silicone Adhere to Cured Silicone?

A question we often hear is: Will new silicone adhere to already cured silicone?

Suppose you're working on a mould and find yourself short on silicone mid-project. There's no need for concern!

Oh no! We’ve run out of silicone!

Typically, you can allow the first batch to cure fully before applying a new layer of silicone on top. This method will generally result in a single, uniform mould. However, there are a few considerations to keep in mind to ensure optimal adhesion and performance.

Firstly, cleanliness is crucial. Any dust, oils, or residues on the cured silicone surface can prevent the new silicone from adhering properly. If this top layer gets any dirt, dust or grime on it, then we advise you to thoroughly clean the surface with isopropyl alcohol and let it dry completely before applying the new layer.

Secondly, the type of silicone matters. Make sure both the initial and subsequent batches of silicone are either the same or compatible with each other. Using the same brand and type of silicone can increase the likelihood of them bonding well.

Doing a second pour to finish off this mould!

Lastly, consider the curing time and environmental conditions. Silicone may not bond well in overly humid or cold conditions. Ensuring a controlled environment can help achieve a seamless cure.

By keeping these points in mind, you can successfully extend or repair silicone moulds without starting from scratch.

The final mould, one uniform piece despite being made in two pours!

PS… generally our silicones will cure against each other and form one piece.

This goofy little rod is made up of the following:

Green = 20A, Yellow = 00-10, Red = 45A, White = 15A, Flesh = 30A, Black = 0A