Sealing force
Softer seals need less force to close but can take a set. Firmer seals need stiffer housings.
Silicone manufacturing guide
Choosing a Shore hardness for your silicone part.
Shore A is the number that appears on nearly every silicone drawing and is understood by almost nobody outside the rubber trade. Here's what it tells you, and what it doesn't.
The basics
Shore A measures how far a small pin sinks into the surface.
A durometer presses a spring-loaded pin into the rubber. Soft materials let it sink further and read lower; firm materials resist and read higher. That's all it measures: surface resistance to indentation.
It doesn't directly tell you how stretchy a material is, how well it recovers, or how it will feel in a particular shape. A thin, soft part and a thick, firm part can feel similar in the hand.
So we treat hardness as one input among several, and we always put physical samples in your hand before locking it in.
A feel for the range
Three broad bands of hardness.
Soft
Ear tips, skin pads, low-force seals and anything that should feel gentle. Easy to deform, can tear if thin.
Medium
Most gaskets, keypads, grips and general seals. The comfortable middle where most parts land.
Firm
Buffers, feet, structural seals and parts that must hold shape under load. Harder to demould from complex tools.
Knock-on effects
Four things that move when you change hardness.
Tactile feel
In keypads and buttons, hardness works together with geometry to set actuation force.
Tear resistance
Softer parts in thin sections tear more easily during demoulding and in use.
Moulding behaviour
Firm materials fill differently and demould less easily from undercuts.
The process
How we settle on a hardness.
The fastest route is almost always samples, not specifications.
Understand the job
What the part does: seal, cushion, grip, click.
Offer a sample range
Parts or plaques in several hardnesses to press, squeeze and fit.
Check in your assembly
Prototype parts tried in the real housing. See prototype tooling.
Record the band
An agreed hardness band written into the specification and checked per batch.
Keep reading
More guides from the workshop.
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Read the guideDesigned and developed in the UK. UK moulding capability, with some higher-volume production placed with trusted partners where that's the right commercial answer.
Get in touch
Tell us the part, the volume, and the timeline.
Rough annual volume, target unit price, and any deadlines. That's enough to work out whether compression, LSR injection or something else is the right tool.
Real people, a real workshop
You deal with the people who make it.
No call centre and no middlemen. When you contact TCI Products, you speak to the team who design, build and check your mould.
- A real Warwickshire workshopUnit 15, Waterloo Park, Bidford-on-Avon, Alcester B50 4JG.
- Real people on the phoneCall the team on 01789 224228, Monday to Friday.
- The same team on every jobDesign, production and aftercare come from the people you see here.
- Part of TCI GroupFive specialist brands, one engineering team. Visit TCI Group.
Thomas LaneManaging Director
George PrestonDesign & Project Manager
Kelly BallingerHead of Partnerships
Jim AndertonProduction Manager
TheodoreEmployee Welfare