Two-Part Platinum Silicone Mix Ratio Calculator
Formulate 1:1 or 10:1 mix weight ratios for platinum or tin-cured liquid mold-making silicone. Avoid wasted material in your shop. Adjust the parameters in the interactive workbench below to get immediate recipe card outputs.
Silicone Mold Box Calculator
INSERT / MASTER OBJECT (DISPLACEMENT)
Scale from 1 prototype to full production run
MEASUREMENT OUTPUTS
Silicone Mold Box Summary
Studio Batch of 1 silicone mold (15cm x 10cm x 6cm) using Smooth-On OOMOO 30: • Per Mold Box: 663g Part A + 663g Part B [Total: 1327g]. • Total Studio Run (1 Units): 663g Part A + 663g Part B [Total Mass: 1327g / 1.33 kg]. • Mix Ratio: 1:1 | Safety Margin: 10%.
MakerRatio • Studio Workshop Batch Sheet
https://makerratio.com • Precision Craft Formula Record
Date: _______________
Batch #: ____________
Project: Smooth-On OOMOO 30 (Mold Box x 1)
Category: Silicone Rubber
Dimensions: Box: 15x10x6 cm (x1)
Mix Ratio: 1:1 | Batch: 1 unit(s)
Specific Gravity: 1.34 g/ml
Safety Spill Margin: 10%
Batch Mix Breakdown (By Exact Weight)
Workshop Safety & Quality Protocol:
[ ] Ambient room temp 70°F–78°F (21°C–25°C) & mold leveled.
[ ] Protective nitrile gloves on & workspace ventilation active.
[ ] Mix thoroughly scraping sides and bottom for 3 full minutes.
[ ] Verify pot life and demold window per manufacturer TDS.
Curing Schedule Log:
Pour Time: ___________
Gel / Tack-Free: ______
Demold Time: ________
Recommended Materials & Tools for this Project
Smooth-On OOMOO 30 Tin Silicone Rubber
Formula: 1:1 mix ratio by volume. Shore 30A hardness. Formulated for casting block molds with zero vacuum degassing required.
Adjustable Acrylic Mold Making Housing Frame
Specification: Modular interlocking plastic barrier walls for sealing and pouring custom silicone block molds without hot glue mess.
Transparency Notice: As an Amazon Associate, MakerRatio earns from qualifying purchases at zero extra cost to you. Product recommendations are selected based on verified Manufacturer Technical Data Sheets (TDS). Always consult chemical safety data before pouring.
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To calculate the exact volume and weight splits for this craft project, the workbench executes the following geometric equations:
Two-Part Liquid Silicone Formulations & Shore Hardness Roster
Shore A & Mix RatiosStoichiometric mix ratios, working pot life, specific gravity densities, and primary craft applications across leading two-part silicones.
| Silicone Brand & Chemical System | Mix Ratio (Wt / Vol) | Specific Gravity | Shore A Hardness | Pot Life / Demold Time | Primary Application |
|---|---|---|---|---|---|
| Smooth-On OOMOO 30 (Tin-Cure) | 1:1 by volume (100A:130B Wt) | 1.34 g/ml | Shore 30A | 30 mins / 6 hours | Beginner 1-piece block molds; no degassing needed. |
| Smooth-On Mold Star 15 (Platinum) | 1:1 by volume or weight | 1.18 g/ml | Shore 15A | 50 mins / 4 hours | Soft, stretchy molds for deep undercuts & delicate masters. |
| Smooth-On Mold Star 30 (Platinum) | 1:1 by volume or weight | 1.18 g/ml | Shore 30A | 45 mins / 6 hours | Rigid, tear-resistant molds for concrete & heavy resin. |
| Dragon Skin 10 NV (Platinum) | 1:1 by volume or weight | 1.07 g/ml | Shore 10A | 20 mins / 5 hours | High-elongation (1000%), ultra-flexible special effects molds. |
| PlatSil 71-11 (Platinum RTV) | 1:1 by weight | 1.10 g/ml | Shore 10A | 20 mins / 4 hours | Fast-demold prototyping & polyurethane resin casting. |
| RTV-1010 Condensation (Tin-Cure) | 10:1 by weight (100A:10B) | 1.15 g/ml | Shore 25A | 45 mins / 16 hours | Budget industrial mold making; high chemical resistance. |
| Smooth-On Sorta-Clear 37 (Platinum) | 1:1 by weight | 1.08 g/ml | Shore 37A | 25 mins / 4 hours | FDA-compliant food safe (chocolate/candy) & glass-clear molds. |
In-Depth Crafting Guide & Density Analysis
Two-part Room Temperature Vulcanizing (RTV) liquid silicones form durable, flexible molds for resin, wax, concrete, and low-melt metals. Whether using platinum-cure (addition cure) or tin-cure (condensation cure) systems, measuring exact Part A and Part B splits on a digital scale ensures complete chemical vulcanization.
This two-part silicone estimator uses manufacturer density presets, calculates 1:1 and 10:1 ratio splits, and adds an essential 10% waste buffer to account for viscous rubber clinging to mixing pitchers and stir sticks.
Frequently Asked Questions (Two-Part Silicone Weight Calculator)
What is 'Cure Inhibition' in platinum silicone and how do you prevent it?
Platinum-cure silicone catalysts are permanently poisoned by contact with sulfur (in modeling clay), latex gloves, amine-cured epoxies, and 3D printed UV resin photopolymers. If poisoned, the silicone touching the master remains sticky and liquid. Prevent this by using nitrile gloves, sulfur-free clay, and post-curing 3D prints in heat (140°F / 60°C for 4 hours) or sealing them with acrylic clear coat.
Why do tin-cure silicones (like OOMOO) specify different ratios by volume vs. by weight?
OOMOO 30 is 1:1 by volume, but Part B is significantly denser than Part A. If weighed on a digital gram scale, the proper stoichiometric ratio is 100g Part A to 130g Part B (1:1.3 by weight). Weighing 1:1 by weight will result in under-catalyzed, soft silicone.
How do you calculate a 10:1 condensation tin-cure silicone mix for 550 grams?
For a 10:1 ratio, Part A is Total × (10/11) and Part B (catalyst) is Total × (1/11). For 550g total: Part A = 500.0 grams and Part B = 50.0 grams.
Is vacuum degassing mandatory for all two-part liquid silicones?
Low-viscosity silicones (like Mold Star 15 or OOMOO) naturally release air bubbles when poured in a thin, pencil-width ribbon from 12 inches above the mold box. High-viscosity or transparent silicones (like Sorta-Clear 37) require vacuum degassing at 29 in-Hg for 2 to 3 minutes to eliminate microscopic bubbles.
What Shore A hardness is best for casting concrete vs. fragile resin miniatures?
For heavy concrete and Jesmonite, use Shore 30A to 40A so the mold holds its shape without bowing. For delicate resin miniatures with extreme overhangs and undercuts, use Shore 10A to 15A (like Mold Star 15 or Dragon Skin) so the silicone stretches without snapping fragile model features.
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