Shore A Durometer Guide: Choosing the Right Silicone Hardness
Durometer is one of the most important specifications when ordering silicone molds. Understanding Shore A hardness helps you select the right mold for your
Kyler Yang · Founder5 min read
Introduction
Durometer is one of the most important specifications when ordering silicone molds. Understanding Shore A hardness helps you select the right mold for your application, balancing flexibility, detail reproduction, and durability.
This guide explains durometer, its measurement, and how to choose the right hardness for your needs.
What Is Durometer?
Definition
Durometer measures the hardness or softness of a material. For silicone molds, the Shore A scale is the standard measurement.
The Shore A Scale
| Range | Description | Typical Use |
|---|---|---|
| 5A - 10A | Ultra-soft | Extreme detail, intricate undercuts |
| 10A - 15A | Very soft | Jewelry, fine detail reproduction |
| 15A - 20A | Soft | Complex gummy shapes, undercuts |
| 20A - 25A | Medium-soft | Standard gummy molds, general purpose |
| 25A - 30A | Medium | Chocolate molds, candy molds |
| 30A - 40A | Medium-hard | Concrete molds, heavy-duty applications |
| 40A - 50A | Hard | Industrial applications |
How Durometer Is Measured
The Test
A durometer instrument presses a specified indentor into the silicone surface:
| Parameter | Value |
|---|---|
| Indentor shape | Cone with flattened tip |
| Applied force | Specified by Shore scale |
| Measurement | Depth of penetration |
| Scale | 0-100 (higher = harder) |
Reading the Scale
`` 0A ───────────────────────────────────── 100A Soft (rubbery) Hard (rigid) ``
Durometer Selection by Application
Gummy Production
| Product Type | Recommended Durometer | Why |
|---|---|---|
| Simple bears | 20A-25A | Balance of flexibility and support |
| Complex characters | 15A-20A | Extra flexibility for undercuts |
| High-volume production | 20A-25A | Durability and consistent release |
| Intricate detail | 15A-18A | Softer silicone captures more detail |
Chocolate Production
| Product Type | Recommended Durometer | Why |
|---|---|---|
| Standard chocolates | 25A-30A | Firm support for clean release |
| High-gloss finish | 25A-28A | Maintains cavity shape under hot chocolate |
| Filled chocolates | 25A-30A | Structural rigidity |
| Decorative pieces | 28A-30A | Sharp detail reproduction |
Candy and Hard Candy
| Product Type | Recommended Durometer | Why |
|---|---|---|
| Hard candy | 25A-35A | High temperature resistance |
| Turkish delight | 20A-25A | Moderate flexibility needed |
| Peanut butter cups | 25A-30A | Balanced properties |
Non-Food Applications
| Application | Recommended Durometer | Why |
|---|---|---|
| Resin casting | 15A-20A | Flexibility for demolding |
| Concrete | 30A-40A | Structural support for heavy material |
| Candles | 20A-30A | Heat resistance and flexibility |
| Soap | 15A-25A | Chemical resistance and release |
| Jewelry | 10A-15A | Maximum detail reproduction |
Durometer vs. Performance
Flexibility
| Durometer | Flexibility | Best For |
|---|---|---|
| 15A | Very high | Complex shapes with deep undercuts |
| 20A | High | Standard complex gummies |
| 25A | Medium | General purpose, chocolate |
| 30A | Low-medium | High-support applications |
| 35A | Low | Heavy-duty, concrete |
Detail Reproduction
| Durometer | Detail Quality | Notes |
|---|---|---|
| 15A | Excellent | Conforms to finest details |
| 20A | Excellent | Very good detail capture |
| 25A | Good | Adequate for most applications |
| 30A | Good | Slight reduction in fine detail |
| 35A | Fair | Best for simple shapes |
Durability
| Durometer | Expected Lifespan | Notes |
|---|---|---|
| 15A | 1,500-3,000 cycles | Softer = more wear |
| 20A | 2,000-4,000 cycles | Good balance |
| 25A | 2,500-5,000 cycles | Optimal for most uses |
| 30A | 3,000-5,000 cycles | Most durable |
| 35A | 3,000-5,000+ cycles | Maximum durability |
The Durometer Selection Flowchart
`` Start → What product? │ ├── Gummy → Is shape complex (undercuts)? │ ├── Yes → 15A-20A │ └── No → 20A-25A │ ├── Chocolate → Is high gloss required? │ ├── Yes → 25A-28A │ └── No → 25A-30A │ ├── Candy → Hard candy? │ ├── Yes → 25A-35A │ └── No → 20A-25A │ └── Non-food → Application type? ├── Resin/Jewelry → 10A-20A ├── Concrete → 30A-40A └── Candles/Soap → 20A-30A ``
Custom Durometer Options
Standard Formulations
| Durometer | Availability | Lead Time |
|---|---|---|
| 15A | Standard | after sample approval, depending on the job |
| 20A | Standard | after sample approval, depending on the job |
| 25A | Standard | after sample approval, depending on the job |
| 30A | Standard | after sample approval, depending on the job |
Custom Durometer
| Factor | Impact |
|---|---|
| Non-standard hardness | +2-3 days lead time |
| Minimum order | May apply |
| Cost premium | +10-20% |
| Availability | Check with manufacturer |
Durometer Myths Debunked
Myth 1: "Softer is always better for detail"
Fact: While softer silicones conform better, extremely soft silicone (below 10A) can be difficult to handle and may tear during demolding. 15A-20A is the practical range for maximum detail.
Myth 2: "Harder means more durable"
Fact: Within the 20A-35A range, harder silicones are generally more durable. However, outside this range, other factors (formulation, filler content) matter more than durometer alone.
Myth 3: "Durometer doesn't affect food safety"
Fact: Durometer is a physical property. All food-grade platinum silicones are FDA compliant regardless of hardness, but the base formulation may vary.
Myth 4: "You can't change durometer after ordering"
Fact: Durometer is determined during manufacturing. You cannot change it afterward. Select correctly at ordering.
Temperature Effects on Durometer
Temperature-Hardness Relationship
| Temperature | Effect on Durometer |
|---|---|
| Below 0°C | Silicone becomes harder (temporary) |
| 0°C - 25°C | Standard durometer rating |
| 25°C - 60°C | Slight softening (reversible) |
| Above 60°C | Significant softening, risk of deformation |
Practical Implications
| Application | Temperature Consideration |
|---|---|
| Hot chocolate pouring | 34°C — minimal effect on 25A+ molds |
| Hot gummy mass | 40-55°C — consider higher durometer |
| Freezer storage | -18°C — temporary hardening, reversible |
| Dishwasher cleaning | 60-70°C — avoid heated dry cycle |
Durometer Testing
In-House Testing
If you need to verify durometer:
| Method | Equipment | Accuracy |
|---|---|---|
| Shore A durometer gauge | Portable gauge | ±1A |
| Comparative test | Side-by-side with known standard | ±2A |
| Manufacturer certificate | From mold supplier | ±0.5A |
When to Test
| Scenario | Recommendation |
|---|---|
| New mold receipt | Verify durometer matches specification |
| Quality issues | Test if durometer degradation suspected |
| Long-term storage | Periodic verification |
| After repair | Verify repaired area properties |
FAQ
Q: What durometer should I choose for gummy bears? A: 20A-25A Shore A is the standard recommendation for gummy bear production, providing the best balance of flexibility and durability.
Q: Can I use a 25A mold for chocolate? A: Yes, 25A is suitable for chocolate. Many chocolate molds use 25A-30A for better structural support.
Q: Does durometer affect FDA compliance? A: No. FDA compliance is determined by the silicone formulation, not the durometer. All our platinum-cured silicones are FDA compliant across the 15A-35A range.
Q: What happens if I choose the wrong durometer? A: Too soft — difficulty demolding complex shapes, faster wear. Too hard — difficulty releasing undercuts, potential product damage.
Conclusion
Selecting the right durometer is essential for optimal mold performance. Match your durometer choice to your product type, shape complexity, and production requirements. When in doubt, our engineering team can recommend the optimal durometer for your application.
*Published: 2026-08-12 | Category: Technical Guide | Read Time: 8 minutes*
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