How to Choose the Right Hardness for Your Custom Silicone Products

Silicone is one of the most versatile engineering materials in the world — found in medical devices, baby products, automotive components, consumer electronics, food processing equipment, and countless everyday items. Its extraordinary range of properties — heat resistance, chemical inertness, flexibility, biocompatibility, and environmental durability — make it the material of choice across industries.

Yet one of the most critical and frequently misunderstood parameters in silicone product design is hardness. Choose the wrong hardness, and a product that looks perfect on paper fails in real-world use — too soft to hold its shape, too hard to provide the required flexibility, or simply wrong for the application's mechanical demands.

At Mitour Silicone, with over 18 years of custom silicone manufacturing experience, hardness selection is one of the first and most important conversations we have with every new client. This comprehensive guide explains everything you need to know about silicone hardness — from the science of the Shore scale to specific hardness recommendations for every major product category.

What Is Silicone Hardness and Why Does It Matter?

Defining Hardness in Silicone

Hardness is a material property that quantifies resistance to permanent deformation when an external force is applied to its surface. In practical terms, it is what you perceive as softness or firmness when you touch, squeeze, or compress a silicone product.

For silicone rubber, hardness reflects:

• Resistance to indentation — how much the surface yields under finger pressure

• Compression resistance — how much the material compresses under load

• Elastic recovery — how completely the material returns to its original shape after deformation

• Tactile feel — the subjective softness or firmness experienced by the end user

Why Hardness Selection Is Critical

Getting hardness right is not merely a technical specification — it directly determines product performance, user experience, safety compliance, and commercial success.

The Shore Hardness Scale: How Silicone Hardness Is Measured

What Is Shore Hardness?

Shore hardness is the internationally recognized standard for measuring the hardness of rubber and elastomeric materials. It was developed by Albert Ferdinand Shore in the 1920s and remains the dominant measurement system for silicone rubber worldwide.

Shore hardness is measured using a durometer — an instrument that applies a standardized force to a standardized indenter pressed against the material surface. The depth of indentation under that force determines the hardness value.

Shore Scale Types for Silicone

The Shore A Scale in Practice

$$\text{Shore A Scale: } 0 \text{ (no resistance)} \rightarrow 100 \text{ (maximum resistance)}$$

How Shore Hardness Is Measured

The measurement process follows ASTM D2240 or ISO 868 standards:

1. The material sample must be at least 6mm thick for accurate reading

2. The durometer indenter is pressed firmly against the flat sample surface

3. The reading is taken at a specified time (typically 15 seconds after contact)

4. Multiple readings are taken at different locations and averaged

5. Temperature is controlled at 23°C ± 2°C for standardized results

Important: Shore hardness readings are only comparable when measured under identical conditions — same durometer type, same contact time, same temperature. Always specify these conditions when communicating hardness requirements.

Liquid Silicone Rubber vs. Solid Silicone Rubber: Hardness Differences

Understanding the distinction between liquid silicone rubber (LSR) and solid silicone rubber (HCR/millable gum) is essential for hardness selection, as the two material types have different hardness ranges, processing methods, and application profiles.

Key Differences Overview

Hardness Ranges by Silicone Type

Liquid Silicone Rubber (LSR) Hardness Range

Solid Silicone Rubber (HCR) Hardness Range

Choosing Between LSR and HCR for Your Application

Complete Silicone Hardness Guide: Shore A Levels and Applications

Shore A 0–10: Extremely Soft Silicone

Properties

Applications

• Realistic prosthetics — Facial prosthetics, theatrical masks, special effects makeup that must mimic the exact feel of human skin

• Soft food molds — Ultra-delicate confectionery molds where minimal demolding force is critical

• Medical simulation — Anatomical training models requiring lifelike tissue feel

• Cushioning inserts — Pressure-relief applications for medical devices

• Sex toys and adult products — Maximum skin-like softness and conformability

Design Considerations

• ⚠️ Requires careful structural support — cannot hold shape independently

• ⚠️ Very thin sections may tear during demolding

• ⚠️ Typically requires Shore C durometer for accurate measurement

Shore A 10–20: Very Soft Silicone

Properties

Applications

• Breast prostheses — Mastectomy prosthetics requiring natural weight, movement, and skin-like feel

• Breast pads and enhancers — Intimate apparel inserts requiring soft, natural feel against skin

• Body-shaping garments — Silicone inserts in shapewear and athletic garments

• Soft cushioning pads — Anti-pressure sore pads for medical and mobility applications

• Gel insoles (ultra-soft) — Maximum cushioning for sensitive feet

• Wearable sensor housings — Soft enclosures for body-worn electronics

Design Considerations

• ⚠️ Limited structural integrity — requires backing or support structure

• ✅ Excellent for skin-contact applications

• ✅ Preferred for products where natural feel is the primary requirement

Shore A 20–30: Soft Silicone

Properties

Applications

• Soft pacifiers — Ultra-soft nipple section for newborns and sensitive infants

• Newborn products — Soft teats, feeding accessories for premature or sensitive babies

• Soft grips — Handles for medical instruments and tools requiring gentle grip

• Flexible tubing — Medical and food-grade tubing requiring high flexibility

• Soft gaskets — Low-pressure sealing applications

• Cosmetic applicators — Soft silicone sponges and makeup tools

Shore A 30–50: Medium-Soft Silicone (Most Popular Range)

Properties

Applications

This is the most widely used hardness range in consumer silicone products:

Design Considerations

• ✅ Excellent for products requiring both flexibility and shape retention

• ✅ Best range for injection molding with fine detail requirements

• ✅ Ideal for products that undergo repeated compression and recovery

• ✅ Most forgiving range for mold design and processing

Shore A 50–60: Medium-Firm Silicone

Properties

Applications

Shore A 60–70: Medium-Hard Silicone

Properties

Applications

Shore A 70–90: Hard Silicone

Properties

Applications

Shore D: Very Hard Silicone (Above Shore A 90)

For applications requiring near-rigid silicone with minimal elasticity, Shore D measurement is used. These materials behave more like hard plastics than traditional rubber:

Hardness Selection Guide by Industry

Medical and Healthcare

Baby and Maternal Products

Kitchen and Food Products

Consumer Electronics

Automotive and Industrial

Beyond Hardness: Other Physical Properties to Consider

While hardness is the primary selection parameter, a complete silicone specification considers multiple interrelated properties:

Key Physical Properties

Temperature Performance

Food-grade silicone maintains its properties across an exceptional temperature range:

$$\text{Operating Range: } -60°C \text{ to } +250°C$$

Chemical Resistance

How to Specify Hardness for Your Custom Silicone Product

Step-by-Step Hardness Selection Process

Step 1: Define the Primary Function

Identify what the product must do mechanically:

• Does it need to seal? → Prioritize compression set resistance (Shore A 40–70)

• Does it need to flex repeatedly? → Prioritize elongation and recovery (Shore A 30–55)

• Does it need to cushion? → Prioritize softness and energy absorption (Shore A 10–40)

• Does it need structural rigidity? → Prioritize hardness and dimensional stability (Shore A 60–90)

Step 2: Consider the End User

• Infant/baby use → Softer (Shore A 25–45) for safety and comfort

• Medical patient → Softer (Shore A 20–50) for comfort and biocompatibility

• Industrial worker → Harder (Shore A 60–80) for durability

• Consumer product → Balanced (Shore A 40–60) for feel and performance

Step 3: Evaluate the Use Environment

• Temperature extremes → Verify hardness stability across the operating range

• Chemical exposure → Confirm chemical resistance at the specified hardness

• Repeated compression → Specify compression set requirements alongside hardness

Step 4: Prototype and Test

• Request samples at 2–3 hardness levels bracketing your target

• Test with actual users in realistic use conditions

• Measure performance against defined acceptance criteria

• Finalize hardness specification based on test results

Step 5: Document the Specification

A complete hardness specification includes:

• Shore scale type (A, C, or D)

• Nominal hardness value (e.g., Shore A 45)

• Acceptable tolerance range (e.g., ±5 Shore A)

• Measurement standard (ASTM D2240 or ISO 868)

• Test conditions (temperature, contact time)

Common Hardness Selection Mistakes to Avoid

Conclusion

Choosing the right hardness for your custom silicone product is one of the most consequential decisions in the product development process. The Shore A scale provides a precise, objective framework for specifying and communicating hardness requirements — but translating a Shore A number into the right real-world product performance requires deep material knowledge and application experience.

The key principles to remember:

• Shore A 0–20 for maximum softness and skin conformability

• Shore A 20–50 for flexible consumer products, baby items, and food contact applications

• Shore A 50–70 for balanced firmness and durability in electronics, seals, and protective products

• Shore A 70–90 for hard-wearing industrial and automotive applications

• Shore D for near-rigid structural silicone components

At Mitour Silicone, our engineering team works with clients at every stage of hardness selection — from initial application analysis through prototype testing and final specification — ensuring that every custom silicone product we manufacture performs exactly as intended.

FAQs

Q: What is the most common silicone hardness for consumer products?

A: Shore A 40–60 is the most common range for consumer silicone products, offering the best balance of flexibility, shape retention, durability, and tactile appeal. Products like phone cases, kitchen utensils, and watch bands typically fall within this range.

Q: Can silicone hardness be customized to an exact Shore A value?

A: Yes. Silicone formulations can be precisely engineered to target specific Shore A values, typically with a tolerance of ±3–5 Shore A. At Mitour Silicone, we can formulate to virtually any Shore A value within the 0–90 range.

Q: Does silicone hardness change with temperature?

A: Yes — silicone becomes slightly softer at higher temperatures and slightly firmer at lower temperatures. However, this change is significantly smaller than for most other elastomers, which is one of silicone's key advantages for applications with wide operating temperature ranges.

Q: What hardness is best for silicone seals and gaskets?

A: Shore A 40–70 is the typical range for sealing applications, with the specific value depending on the sealing pressure, surface finish, and compression set requirements. Higher pressure applications generally require harder silicone (Shore A 60–70) for better compression set resistance.

Q: Is softer silicone always safer for baby products?

A: Not necessarily. While softness contributes to comfort, the most important factor for baby product safety is material certification (food-grade, FDA, LFGB). The appropriate hardness depends on the specific product — a teether needs enough resistance for effective chewing (Shore A 35–45), while a pacifier nipple should be softer (Shore A 25–35).

Q: How do I request a specific hardness for a custom silicone product from Mitour Silicone?

A: Simply specify your target Shore A value and tolerance when submitting your product inquiry. Our engineering team will confirm the feasibility, recommend any adjustments based on your application requirements, and provide samples at your specified hardness for testing and approval before production.

Q: Can the same product use different hardness silicone in different sections?

A: Yes — this is called multi-durometer or overmolding. It's commonly used in products like toothbrush handles (hard core, soft grip surface) or medical devices (rigid structural section, soft patient-contact section). Mitour Silicone has extensive experience with multi-durometer silicone product manufacturing.

Partner with Mitour Silicone for Expert Hardness Selection

Choosing the right silicone hardness requires more than a chart — it requires manufacturing experience, material science expertise, and a deep understanding of your product's performance requirements. Mitour Silicone brings all three to every custom project.

With 18 years of silicone manufacturing experience, ISO 9001 quality management, and complete FDA/LFGB certification capability, we are your trusted partner from hardness specification through certified finished product.

[Contact Us Today →] Share your product requirements, request hardness samples, or consult with our engineering team about the optimal silicone specification for your custom product!