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Choose a Product - 3 of 10Updated 13 November 2026

Final Hardness

Final hardness is the rigidity of a Plastiform impression after it has fully cured. It determines whether you can extract the impression from a complex shape without tearing it, and which measuring instruments you can use on it.

All Plastiform products fall into one of three hardness categories measured on the Shore A scale. Only P51 SD is given in Shore D.

Shore A is an international standard for elastomers that runs from 0 (very soft) to 100 (very hard).

Flexible: 40 Shore A and Below

Flexible impressions bend, stretch, and compress easily.

This lets you extract them from threaded holes, grooves, or any shape with a removal constraint the product accepts. The impression deforms on the way out, then returns to exact geometry as soon as the stress is released.

Because they are soft, flexible impressions cannot be inspected using contact pressure from calipers or CMM probes. Measure them with non-contact instruments only: profile projectors, scanners, vision systems, or optical microscopes.

Typical products: F20, F30 Visual, F30 Max, F40, P25, P35, M25

Use Flexible when:

  • The shape has undercuts, threads, or grooves
  • You have a non-contact measuring system
  • You do not need to slice the impression, or you pick one of the Flexible products the Double Blade Cutter accepts: F40, P25, P35 or M25

Medium: Between 40 and 80 Shore A

Medium hardness works for most applications. The impression is strong enough to extract from simple shapes and rigid enough for a cross cut.

Medium impressions can be sliced with the Double Blade Cutter to produce a thin cross section for profile projection or vision system analysis. This makes them the most versatile category for dimensional inspection.

For a Medium product, the technical sheet says whether contact measurement is possible. Non-contact methods remain the safer choice for precision.

Typical products: F50, F65, M60, M70

Use Medium when:

  • You want to slice the impression with the Double Blade Cutter
  • The shape has a low to moderate removal constraint
  • You need a balance between ease of removal and measurement adaptability

Rigid: 80 Shore A and Above

Rigid impressions barely deform.

They feel solid, almost like plastic. This makes them ideal for simple shapes with zero removal constraint where the impression slides straight out.

In exchange for the lack of flexibility, you gain the ability to measure with contact instruments: calipers, micrometers, CMM probes, and roughness testers. Keep in mind that contact measurement will always deform the impression slightly, so results are less precise than non-contact methods.

If you use a Rigid product on a shape with any undercut or thread, the impression will lock in place. Forcing it out will break it.

Typical products: F85, P80 Ra, P51 SD, M80 LP, M90

Use Rigid when:

  • You have no choice but to measure with a contact instrument
  • The shape is simple and straight with no undercuts
  • The impression is long and thin. Rigidity helps it hold its shape without bending under its own weight

Shore A vs Stretchability

Shore A measures rigidity, not stretchability. Two products with the same Shore A can behave very differently during extraction.

F30 Max and F30 Visual both sit at 30 Shore A. Both are Flexible. But F30 Max accepts a removal constraint of 40%, against 20% for F30 Visual, which makes it suitable for shapes with severe undercuts. F30 Visual has a glossy black surface that makes it ideal for visual inspection.

For extraction, check the product’s removal constraint percentage, not just Shore A.

See Removal Constraint for further information about this topic.

Related Pages

Final Hardness
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