Addition vs. Condensation Silicone: Which Cures Faster & Lasts Longer?
Addition-cure silicone uses a platinum catalyst that triggers cross-linking when heat or time is applied, producing no by-products. Condensation-cure silicone relies on tin catalysts plus atmospheric moisture, releasing acetic acid or alcohol as it hardens. Both turn liquid into flexible rubber, but their chemistry decides speed and lifespan.
Buyers grab whichever tube is cheaper or labeled “mold-making,” unaware the wrong type can lock up a 3-D printer or shrink a prosthetic limb weeks later. Hobbyists see “fast cure” and assume it’s the same inside, then wonder why one mold warps while another stays rock-solid for years. The mix-up costs time, money, and reputation.
Key Differences
Addition silicone reaches full strength in 30 min to 4 hr, shrinks <0.1%, and resists 200 °C+ for decades. Condensation grabs shape in 10–60 min but keeps shrinking 0.3–0.6% over days and slowly reverts above 150 °C. Platinum loves clean, dry surfaces; tin forgives dusty, humid benches.
Which One Should You Choose?
Pick addition for long-life molds, medical devices, or electronics that must stay precise. Grab condensation for quick repairs, hobby casts, or outdoor gaskets where cheap and fast beats perfect accuracy. Match cure to your timeline, then match chemistry to your environment.
Can I speed up condensation cure with heat?
Brief warmth helps, but too much traps released alcohol, causing bubbles and weak spots.
Does addition silicone stick to everything?
No—its low surface energy needs primer on glass, metals, and some plastics.
Why does my tin-cure mold shrink weeks later?
Post-cure shrink continues until all moisture and by-products escape; ventilate and wait longer before first pour.