Why enhance a material?

Raw materials rarely arrive with the exact properties a product needs. Enhancement processes deliberately change a material to improve its strength, hardness, durability, workability or appearance. The main routes are:

• Timber: seasoning, preservation, lamination and steam bending.
• Metal: heat treatments (annealing, hardening, tempering, case hardening) and work hardening; alloying.
• Polymer: additives — plasticisers, fillers, pigments, fibre reinforcement.

Seasoning and treating timber

Freshly felled timber is full of water. Seasoning reduces its moisture content so it becomes stronger, more stable and less likely to warp, split or rot.

• Air seasoning — stacked outdoors under cover; cheap but slow (months–years).
• Kiln seasoning — heated, humidity-controlled chamber; fast and reaches lower moisture content, but uses energy.

Also: preservatives (e.g. tanalising / pressure treatment) protect against fungal and insect attack for outdoor use.

Why season timber?

Your turn — moisture content

Heat-treating metals

Controlled heating and cooling changes a metal’s internal structure and therefore its properties:

• Annealing — heat then cool slowly; softens the metal and relieves internal stress so it can be worked.
• Hardening — heat then quench (cool rapidly in water/oil); makes steel harder but more brittle.
• Tempering — gently reheat a hardened part; reduces brittleness and restores some toughness (a controlled trade-off).
• Case hardening — gives a hard, wear-resistant skin over a tough core (e.g. gears).

Match treatment to its effect

Tap a treatment, then tap the effect it has on the metal.

After hardening…

Work hardening

Work (cold) hardening occurs when a metal is repeatedly bent, hammered or rolled cold. The grain structure distorts, making the metal harder and stronger but more brittle — bend a paperclip back and forth and it eventually snaps.

The effect can be reversed by annealing, which recrystallises the grains and softens the metal again.

Alloying

Alloying mixes a base metal with other elements to enhance properties that the pure metal lacks:

• Stainless steel (iron + chromium) — chromium gives corrosion resistance.
• Duralumin (aluminium + copper) — much stronger than pure aluminium yet still light.
• Brass (copper + zinc) — harder, more corrosion-resistant and easier to machine than copper.

Why add chromium to steel?

Enhancing polymers with additives

Polymers are modified by mixing in additives before moulding:

• Plasticisers — make a rigid polymer (e.g. PVC) flexible for hoses and cable sheathing.
• Fillers — bulk out the polymer to cut cost and can add stiffness.
• Pigments & UV stabilisers — add colour and slow degradation in sunlight.
• Fibre reinforcement — glass or carbon fibres greatly increase strength (composites).

Lamination and bending

• Bent (glue) lamination — thin timber strips (laminae) glued and clamped in a former set into strong, curved shapes (e.g. glulam beams, chair frames).
• Steam bending — timber softened with steam then bent around a former.
• Laminated glass — a plastic interlayer bonds glass sheets so they hold together if broken (car windscreens).

Which material does it enhance?

Tap an enhancement process, then tap the material group it belongs to.

The big ideas to know

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