It is the greatest fear of every mold maker: after hours of waiting, the silicone rubber is still tacky or even completely liquid around the original. This phenomenon is called cure inhibition (curing disruption). It is not only frustrating, but it can also damage your precious master model. In this article we explain how it occurs and how you can prevent it in the future.
Cure inhibition occurs when the chemical reaction of the silicone is blocked by external substances. Especially with addition silicones (platinum silicones), this is a well-known problem. The most common culprits are:
To ensure your silicone rubber cures flawlessly, follow these fixed steps from our troubleshooter.
Guessing or measuring with a measuring cup is not sufficient for silicone rubber. The density of component A and B often differs. Therefore, always use a digital scale and strictly maintain the 1:1 mixing ratio by weight. Even a small deviation can result in a mold that doesn't feel fully 'set'.
Mixing is more than just stirring. Mix the components carefully and do not forget to scrape the walls and bottom of the cup. For a 100% homogeneous mixture, we recommend the 2-
cup mixing method: mix the silicone first in the first cup, pour it into a second clean cup and mix briefly again. This prevents unmixed silicone from the walls from ending up in your mold.
Has the damage already been done and does your mold still feel slightly tacky on the surface after the full curing time? Don't throw the mold away immediately. You can often neutralize the stickiness by lightly rubbing the mold with talcum powder. This neutralizes the tacky feeling and allows you to still use the mold for your castings.
Before starting a large project, we always recommend doing a small 'drop test' on your original. This immediately shows whether the material of your model (such as 3D resin) disrupts the curing. If that is the case, use a suitable primer as a barrier layer.
Can't quite figure it out despite these tips, or do you have a specific question about your unique project? Don't worry, the experts at Polyestershoppen are ready for you. Whether it's about the right Shore hardness, preventing cure inhibition or technical advice for industrial applications: we are happy to help you achieve a perfect end result.
View our full silicone rubber troubleshooter for more in-depth information or contact us directly for personal advice by phone, chat or email. Together we will make your project a success!
In that case, there is likely severe cure inhibition or a weighing error. Carefully remove the liquid silicone with a spatula and clean your model with a solvent before trying again.
No, this does not work with 1:1 silicone rubber. It disrupts the chemical balance, causing the mold to remain sticky or become brittle.
Yes, silicone cures faster in a warm environment, but be aware: the processing time (pot life) also becomes shorter, and there may be more air entrapment and shrinkage at temperatures above 25-30 degrees Celsius.
Do you have a specific question? Call one of our specialists for free advice +3185 0220090
