Shore 20A is very soft (baby nipples, facial brushes). Shore 40A is the versatile middle (teethers, kitchen utensils, beauty applicators). Shore 60A is firm yet flexible (seals, keypads, phone cases). Shore 80A is rigid rubber (feet, bumpers, industrial gaskets). If you pick the wrong hardness, the part either feels too cheap, fails its sealing function, or breaks in the customer's hand. This guide covers every common silicone product category and which hardness works.
Why hardness is the #1 product-design decision buyers get wrong
A new buyer sends a drawing to a factory. The factory quotes. The buyer approves samples. The samples feel "off" — too soft, too firm, too bouncy, too hard. The buyer assumes the factory made a mistake. The factory says "you did not specify hardness."
Hardness — measured on the Shore A durometer scale for silicone — determines how the product feels in the hand, how it seals, how it wears, and how it performs over time. It is not a nice-to-have spec; it is the first parameter on any silicone part drawing.
This guide walks through the common hardness ranges, what they feel like, and which product categories they fit.
The Shore A scale for silicone at a glance
| Shore A | Feel | Common analog | Typical applications |
|---|---|---|---|
| 10–20A | Very soft, gels like a gummy bear | Memory foam, jelly | Baby nipples, very soft facial puffs, roll-up mats |
| 20–30A | Soft, pliable | A stress ball | Baby teethers, beauty blenders, soft grip handles |
| 30–40A | Medium-soft, "silicone kitchenware" feel | A spatula you've used for 6 months | Kitchen utensils, baking mats, food storage bags |
| 40–50A | Medium, balanced softness | A yoga block | Baby bowls, pet bowls, phone pouches, cosmetic containers |
| 50–60A | Medium-firm, firm yet flexible | A keyboard key | Keypads, remote covers, cable boots, suction cups |
| 60–70A | Firm rubber | A car tire sidewall | Seals, gaskets, O-rings, industrial feet |
| 70–80A | Very firm, almost rigid | A hockey puck | Bumpers, feet, industrial grips, vibration dampeners |
| 80A+ | Hard rubber | A sneaker sole | Heavy industrial parts, precision connectors |
Shore 20A: baby nipples, facial brushes, soft grip
Feel: Squeezes easily, returns slowly. Compresses to half its thickness with two fingers.
Best for:
- Baby bottle nipples (typically 15–25A)
- Very soft facial cleansing brushes
- Roll-up silicone mats that need to fold flat
- Medical soft-touch grips
- Seals that need to conform to uneven surfaces
Watch out: Shore 20A is harder to mold cleanly. It flashes more, deforms faster in storage, and can stick to itself. Expect slightly higher defect rates and a narrower color range.
Shore 30–40A: the "silicone kitchenware" default
Feel: The classic "silicone spatula" feel. Flexible enough to fold over a bowl edge, firm enough not to collapse under food weight.
Best for:
- Spatulas, spoonulas, whisks
- Baking mats, baking cups
- Food storage bags
- Baby teethers (30–40A)
- Facial mask applicators (35–45A)
This is the most common hardness for consumer silicone products. If you don't know where to start, 40A is a safe default.
Shore 50A: balanced medium, multi-purpose
Feel: Firm but squeezable. You can press a fingernail into it, but it doesn't collapse easily.
Best for:
- Baby bowls and plates
- Pet bowls and pet mats
- Phone pouches and cable organizers
- Cosmetic containers
- Wine tumblers
- Kitchen utensils that need more structure than 40A
Why 50A? If your product holds shape (a bowl, a tumbler) but still needs to be squeezable, 50A is usually the sweet spot. 40A is too floppy for bowls; 60A is too hard for baby-safe feel.
Shore 60A: keypads, suction cups, seals
Feel: Firm rubber. A fingernail leaves a small indent. Feels like a TV remote button.
Best for:
- Remote control keypads and membrane buttons
- Suction cups (need firmness to hold vacuum)
- Cable boots, wire grommets
- Door seals, window seals
- Phone cases with grip texture
- Keyboard wrist rests
Watch out: 60A is too firm for food-contact products where softness is part of the experience. Don't use it for baby teethers or kitchen utensils unless you have a specific reason.
Shore 70A: industrial seals, O-rings, gaskets
Feel: Very firm. Feels like a car tire sidewall.
Best for:
- O-rings, gaskets, flange seals
- Industrial feet and bumpers
- Vibration dampeners
- Automotive boots and connectors
- Waterproof seals for enclosures
This is the workhorse for industrial silicone parts. Most O-rings are 70A.
Shore 80A+: hard rubber
Feel: Almost rigid. Bends but doesn't flex easily. Feels like a sneaker sole.
Best for:
- Heavy-duty bumpers
- Anti-slip feet for appliances
- Precision connector parts
- Industrial grips that must not deform under load
How to pick the right hardness for your product
Ask these four questions:
1. What is the hand feel your customer expects?
If the product is marketed as "soft" or "gentle," start at 30A. If it's marketed as "durable" or "firm," start at 50A.
2. Does it seal against another surface?
If yes, 50–60A is the range. Too soft and it deforms; too hard and it doesn't conform.
3. Does it hold liquid or shape?
Bowls, tumblers, cups need 40–50A. Below 40A they collapse; above 60A they feel plastic.
4. Does it flex repeatedly?
Keypads, hinges, cable boots need 50–60A. Softer materials fatigue faster; harder materials crack.
The tolerance problem: ±5 Shore A
Hardness is not a precise spec. Realistically, any molded silicone part has a tolerance of ±5 Shore A. This means:
- A part specified at 40A might measure 35A on one side, 45A on the other
- That is normal and acceptable for consumer products
- For precision sealing applications, specify ±3 Shore A (at higher cost)
- For medical devices, specify ±2 Shore A (with Cpk study required)
Practical implication: If your product is designed to be "40A," do not panic if samples measure 38A or 42A. What matters is consistency across production.
How hardness interacts with color and temperature
Hardness is set by the silicone compound formulation. Color pigmenting typically reduces hardness slightly (by 2–5 Shore A). If you need 40A in red but the compound supplier only stocks 40A white, the red version might run at 37–38A.
Temperature also affects feel:
- Cold silicone (refrigerator, winter) feels 5–10 Shore A firmer
- Hot silicone (oven, boiling water) feels 5–10 Shore A softer
- Design your product for the coldest temperature it will experience
Testing hardness yourself
You can buy a Shore A durometer for $50–$150 online. For ongoing quality control, this is worth it. Test:
- Three points on each part
- Average the three readings
- Compare to your spec ±5A
- Log results in your supplier's FAI report
If you don't want to invest in a durometer, ask your factory to include hardness readings on the first article inspection (FAI) report. Real factories do this automatically.
FAQ
Q: Can I mold multiple hardnesses in one part?
A: Yes, via overmolding (two-shot LSR). Common for grips: firm core at 60A, soft outer grip at 30A. This is more expensive but produces premium-feeling products.
Q: What hardness is a baby bottle nipple?
A: Typically 15–25 Shore A. Below 20A for newborns, 20–25A for older babies.
Q: What hardness is a silicone phone case?
A: Usually 50–60A. Below 50A the case stretches too much; above 60A it's hard to install.
Q: Can I change hardness after tooling is cut?
A: Yes — hardness comes from the material, not the mold. You can switch compound without changing tooling. But each hardness requires its own compliance test if food-contact.
Q: What is the most common hardness for Amazon kitchenware?
A: 40A for spatulas, 50A for baking mats, 50A for storage bags.
Q: Does hardness affect material price?
A: Slightly. Below 20A and above 70A, materials are typically 10–30% more expensive because they are specialty compounds. Mid-range (30–60A) is commodity-priced.
Q: Can I test hardness without a durometer?
A: Roughly yes: press your thumbnail into the part. If it leaves a deep indent, it's under 30A. If it leaves a shallow indent, it's 40–50A. If it barely indents, it's 60A+. This is a rough estimate only.
See our Silicone Hardness Chart for a printable reference, or ask for a hardness recommendation for your product category.