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Why Won’t My Silicone Cure?
One of the most frustrating issues resin and mold artists face is silicone that just won’t set properly. Symptoms can include a sticky surface, uncured edges, or even silicone that won’t dry at all. Not only is this messy and uncomfortable to handle, but it also means wasted materials and time.
The good news? Most curing problems come down to a few common factors and they’re easy to prevent once you know what to watch for.
Why Does Silicone Fail to Cure?
Silicone curing issues usually trace back to three main causes:
- Curing inhibition – Certain materials interfere with the curing reaction.
- Mixing mistakes – Incorrect ratios or poor stirring lead to uneven curing.
- Environmental factors – Temperature and humidity affect drying speed and quality.
By controlling these three areas, you can dramatically reduce the chances of curing failure.
How to Prevent Curing Problems
1. Avoid Curing Inhibition
- Master molds: Only use dry, compatible materials. Avoid fresh wood (contains moisture), UV-finished items, candles, and 3D-printed photosensitive materials, as they can all cause curing failure. If unsure, always spot-test by brushing a little silicone onto the mold before use.
- Adhesives: Double-sided tape and hot-melt glue can react with silicone. If you need to secure the master mold, use just a small dot of hot glue at the base, too much may stop the silicone from drying.
2. Mix Accurately and Thoroughly
- Ratio: Mix the 2 parts at a strict 1：1 weight ratio.
- Stirring: Scrape the sides and bottom of the cup while mixing, and stir for at least 3–5 minutes if working by hand. This ensures a uniform blend and proper curing.
3. Control Temperature and Humidity
- Keep your workspace at 73–78°F (23–26°C) with humidity below 50–60% RH.
- On rainy or humid days, cover the mold container after pouring to prevent excess moisture and dust from interfering with the curing process.
Can Uncured Silicone Be Saved?
- Sticky surfaces: Sprinkle baking soda or talcum powder on the surface, then gently press to absorb the grease and reduce tackiness.
- Completely uncured silicone: Sadly, this cannot be rescued. The best option is to discard the failed pour, clean the master mold with an alcohol wipe, and start fresh.