Silicone Needed
1.12 lb
Volume
28.6 in³
Cost
$25
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Inputs
Result
Mold box = 5" × 4" × 2.5" = 50 in³. Object = 24 in³. Silicone = (50 - 24) × 1.10 waste = 28.6 in³ = 0.90 lb at ~25.5 in³/lb.
Inputs
Result
Object = π × 1.5² × 5 = 35.3 in³. Mold box = π × 2² × 5.5 = 69.1 in³. Silicone = (69.1 - 35.3) × 1.10 = 37.2 in³.
The amount depends on your object size and mold wall thickness. A 4" × 3" × 2" box mold with 0.5" walls needs about 0.90 lb of silicone (~$20 for tin-cure). Larger objects or thicker walls increase the volume proportionally.
| Silicone Type | Cost/lb | Mold Life | Best For |
|---|---|---|---|
| Tin-Cure | $22 | 20–50 casts | Prototyping, short runs |
| Platinum-Cure | $32 | 100+ casts | Production, food molds |
| Food-Safe | $38 | 100+ casts | Chocolate, candy, ice |
Standard wall thickness is 0.5" (13mm) for most molds. Thin walls (0.25") work for small, simple shapes. Thick walls (0.75–1") are needed for large or heavy castings to prevent the mold from flexing during demolding.
Tin-cure (condensation cure) is cheaper at ~$22/lb but shrinks slightly over time and has a shorter mold life (20–50 casts). Platinum-cure (addition cure) costs ~$32/lb but offers negligible shrinkage, longer mold life (100+ casts), and food-safe options.
Mix silicone slowly to minimize air entrapment, then vacuum degas for 3–5 minutes at 29" Hg. Pour in a thin stream from a height to break bubbles. For small molds without a vacuum chamber, tap the mold container against the table to release trapped air.
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Last Updated: Mar 19, 2026
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