Fast-Cast Polyurethane Resin (Smooth-Cast 300) for Hemisphere / Dome Mold Calculator
Pre-loads specific gravity (1.05) and 1:1 mix ratio to calculate exact Part A & Part B weights with cup scraping buffer.
A standard Hemisphere / Dome Mold (Ø10 cm minus 150 cm³ master) requires 127g (4.47 oz / 0.28 lbs) of Fast-Cast Polyurethane Resin (Smooth-Cast 300). Mix 63.4g Part A with 63.4g Part B (8% buffer included).
Casting Material & Volume Mode
Pre-loads specific gravity and 1:1 ratio by weight.
Geometry determines the container-volume formula. Use water displacement when the cavity is irregular.
Volume displaced by your master object inside the box.
Compensates for resin clinging to mixing paddles and cup walls (8% recommended).
Includes 8% waste buffer at SG 1.05
Ratio part: 1
Ratio part: 1
Net volume before buffer
Order Fast-Cast Polyurethane Resin (Smooth-Cast 300) Kit
High-tear strength Fast-Cast Polyurethane Resin (Smooth-Cast 300) with verified 1:1 ratio. Ideal for bubble-free casting.
Fast-Cast Polyurethane Resin (Smooth-Cast 300) vs Alternative Casting Compounds
Compare specific gravities, mix ratios, working times, and cure speeds across casting compounds.
| Material / Specification | Specific Gravity | Mix Ratio | Pot Life | Demold Time |
|---|---|---|---|---|
| Fast-Cast Polyurethane Resin (Smooth-Cast 300)ACTIVE | 1.05 | 1:1 (weight) | 3 min | 0.25 hrs |
| RTV-2 Platinum Silicone (Smooth-On Mold Star 15/30) | 1.07 | 1:1 (weight) | 30 min | 6 hrs |
| RTV-2 Tin Cure Silicone (Condensation Cure) | 1.12 | 10:1 (weight) | 45 min | 12 hrs |
| Jesmonite AC100 (Eco-Resin) | 1.75 | 2.5:1 (weight) | 12 min | 2 hrs |
| Jesmonite AC730 (Stone Casting) | 1.85 | 5:1 (weight) | 15 min | 4 hrs |
| Deep Pour River Epoxy (2:1 Ratio) | 1.11 | 2:1 (weight) | 90 min | 48 hrs |
Step-by-Step Mix Ratio Derivation: Fast-Cast Polyurethane Resin (Smooth-Cast 300)
How displacement volume, specific gravity, and ratio split combine into final scale weights.
Calculates the empty fluid cavity by taking the gross 261.8 cm³ hemisphere containment volume and deducting the 150 cm³ displaced by the master model.
Multiplies fluid volume by the specific gravity of Fast-Cast Polyurethane Resin (Smooth-Cast 300) (1.05 g/cm³) plus an 8% buffer for cup scraping and pouring loss.
Distributes batch mass according to the exact 1:1 ratio by weight.
Engineering Specifications & Troubleshooting Guide: Fast-Cast Polyurethane Resin (Smooth-Cast 300)
Factory-tested parameters, common failure modes, and workbench best practices.
- Ultra-fast curing polyurethane: pot life is only 3 minutes, turns bright porcelain white, and demolds in 10-15 minutes.
- Have all cups, molds, and clamps staged before combining Part A and B; you only have 90 seconds to pour.
- Moisture sensitive: keep bottles tightly capped with dry gas nitrogen blanket (XTEND-IT) to prevent foaming.
Hesitating during the pour; the liquid turns milky and thickens rapidly inside the cup if you take longer than 2.5 minutes.
Frequently Asked Questions: Fast-Cast Polyurethane Resin (Smooth-Cast 300)
Mix ratios, degas guidelines, cure times, and mold making tips.
Q1What is the mix ratio of Fast-Cast Polyurethane Resin (Smooth-Cast 300)?
Q2How much Fast-Cast Polyurethane Resin (Smooth-Cast 300) do I need for a Hemisphere / Dome Mold?
Q3How long before I can demold Fast-Cast Polyurethane Resin (Smooth-Cast 300)?
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