Part 1 What Are Soft Plastic Fishing Lures Made Of? (PVC, Plastisol & Plasticizers Explained)

Soft plastics aren’t rubber — they’re engineered PVC systems where plasticizer ratio and formulation control determine whether a bait feels alive or stiff.

What are soft plastic fishing lures made of?

Soft plastic fishing lures are made from PVC (polyvinyl chloride) resin suspended in liquid plasticizer, a material system known as plastisol. When heated to approximately 320–350°F, the PVC resin particles absorb plasticizer, fuse into a homogeneous melt, and then solidify into a flexible finished lure after cooling. Additives such as salt, stabilizers, pigments, and elastomers are used to fine-tune density, durability, and action.

If you want a deeper technical breakdown of how plastisol behaves during heating and fusion, see the science of plastisol and how soft lures are engineered for action.

Most anglers assume soft plastic fishing lures are simply “rubber,” but that assumption ignores the engineered material system behind them. These baits are precision-formulated PVC plastisol systems where resin selection, plasticizer balance, additive loading, and controlled fusion determine final flexibility, density, durability, and action. Small changes at the formulation level produce measurable differences in how a lure moves, feels, and performs in the water.

Soft plastic fishing lures are often confused with rubber or silicone, but their material systems and processing methods are fundamentally different.

Soft Plastic Lure Materials Comparison

Property	PVC Plastisol (Soft Lures)	Rubber	Silicone
Base Material	PVC resin + liquid plasticizer	Natural or synthetic rubber polymers	Silicone elastomer
Processing	Heated to ~320–350°F to fuse	Vulcanized (chemical crosslinking)	Cured via heat or catalyst
Flexibility Control	Adjusted by plasticizer ratio	Controlled by formulation and crosslinking	Generally soft and elastic
Density Control	Easily adjusted with salt or additives	Limited control	Limited control
Buoyancy Tuning	Yes (via fillers/additives)	Difficult	Moderate
Recyclable/Re-meltable	Yes (thermoplastic)	No (thermoset once cured)	No (thermoset once cured)
Typical Use in Fishing Lures	Primary material for soft plastics	Rarely used	Used in specialty baits

Most modern soft plastic fishing lures are PVC plastisol systems because they allow precise control over flexibility, density, action, and durability.

This article breaks down the three core factors that determine how a soft plastic behaves:

1. PVC — the structural backbone

2. Plasticizers — the flexibility control

3. Formulation differences — why not all plastics act the same

1. PVC: The Backbone of Soft Plastics

At the core of nearly every traditional soft plastic lure is PVC — Polyvinyl Chloride.

PVC starts as a fine white powder. In this form, it is rigid and brittle. On its own, PVC behaves more like plumbing pipe than a fishing worm.

What PVC Actually Is

PVC (polyvinyl chloride) is a thermoplastic polymer made of repeating vinyl chloride units. As a thermoplastic, it softens when heated and solidifies again when cooled without undergoing a permanent chemical change. This reversible behavior is what makes plastisol processing possible. In its unmodified form, PVC is rigid and brittle; flexibility only occurs when plasticizers are introduced to separate and lubricate the polymer chains

At the molecular level, PVC consists of long-chain polymers that naturally pack tightly together. When heated alone and allowed to cool, PVC forms a hard, inflexible solid. Only when plasticizer molecules are blended into the system do those chains gain mobility, allowing the finished lure to bend, stretch, and recover in the water.

These chains:

• Are stiff by nature

• Do not flex easily

• Lock together tightly when cooled

If you heat PVC powder alone and let it cool, you do not get a soft bait. You get a hard chunk of plastic.

So why does it become soft in fishing lures?

Because PVC is only half the system.

2. Plasticizers: The Flexibility Engine

Plasticizers are liquid additives blended into PVC before heating.

When plastisol is heated to approximately 320–350°F, the PVC resin particles fuse into a homogeneous solid that remains flexible after cooling.

Their job is simple:

They force the PVC chains apart.

Plastisol Fusion Process: PVC resin particles suspended in liquid plasticizer heat to 320–350°F, fuse into a homogeneous material, and solidify into a flexible soft plastic after cooling.

What Plasticizers Do

When plasticizer is added:

• It wedges itself between PVC molecular chains

• It reduces internal friction

• It allows the chains to slide past each other

The more plasticizer added, the more flexible the finished material becomes.

This is the single biggest reason some soft plastics feel supple while others feel stiff.

The Basic Rule

More plasticizer =

• Softer feel

• More stretch

• More “life” in the water

Less plasticizer =

• Firmer body

• More durability

• Tighter action

This ratio is not random. It is engineered.

Soft vs Firm Soft Plastic Formulations

Property	High Plasticizer (Soft)	Low Plasticizer (Firm)
Shore A Hardness	5A–15A	20A–35A
Flexibility	Very high	Moderate
Stretch	High elongation	Lower elongation
Tear Resistance	Lower	Higher
Action in Water	Subtle / “alive”	Tighter / controlled
Durability	Lower	Higher
Best Use	Finesse, trout, panfish	Flipping, heavy cover

3. Why Not All Soft Plastics Feel the Same

Two baits can look identical but feel completely different.

That difference usually comes down to formulation control in three areas:

1. Plasticizer Ratio

A high-plasticizer finesse worm will:

• Collapse easily

• Quiver with minimal movement

• Feel oily or extremely soft

A low-plasticizer flipping bait will:

• Hold shape under pressure

• Resist tearing

• Feel dense or firm

2. Resin Particle Size

Not all PVC resins are identical.

Finer resins:

• Fuse smoother

• Produce clearer plastisol

• Create more uniform texture

Coarser resins:

• May feel slightly grainier

• Affect clarity

• Change how additives disperse

3. Additive Loading

Salt, stabilizers, pigments, and other additives all alter performance.

For example:

Heavy salt loading:

• Increases density

• Dampens action

• Makes a bait feel more rigid

Floating agents:

• Reduce density

• Increase buoyancy

• Can soften perceived structure

Every additive shifts the behavior of the final lure.

How Additives Change Soft Plastic Performance

Additive	Effect on Density	Effect on Action	Effect on Feel
Salt	Increases	Dampens	Firmer
Floating Agents	Decreases	Increases lift	Softer perceived
Elastomers	Neutral	Smoother	Rubber-like
Stabilizers	Neutral	None	Heat stability

Why Some Soft Plastic Fishing Lures Feel “Alive"

When anglers say a bait feels alive, they are usually describing:

• High flexibility

• Low stiffness resistance

• Rapid recovery after deformation

• Minimal dampening of movement

Technically, this comes from:

• Proper plasticizer balance

• Controlled fusion during heating

• Correct additive loading

• Clean resin dispersion

If the formula is off — even slightly — the bait may:

• Feel rubbery

• Snap back too slowly

• Resist subtle rod input

• Appear stiff in cold water

The “alive” feeling is not accidental. It is the result of precise chemical balance.

Why Some Baits Feel Stiff or Rubbery

Stiffness can come from:

• Lower plasticizer ratios

• Excessive salt

• Overheating during fusion

• Incorrect plasticizer type

• Poor resin dispersion

  
  

Rubbery texture often indicates:

• Too much elastomeric additive

• Incomplete fusion

• Excess stabilizer interaction

• Cold-temperature performance issues

  
  

These are formulation decisions, not random outcomes.

The Critical Reality

Soft plastic performance is not determined by shape alone.

You can have the best mold design in the world. If the plastisol formula is wrong, the bait will not perform correctly.

Action begins at the molecular level.

PVC provides structure, plasticizers control flexibility, and additives fine-tune behavior.

Change any one of those, and the bait changes.

Frequently Asked Questions

Are soft plastic fishing lures made of rubber?

No. Most soft plastic fishing lures are made from PVC-based plastisol systems, not rubber or silicone. Although they may feel flexible, their softness comes from plasticizers blended into PVC resin. The final texture and action are controlled through formulation and heating, not natural rubber compounds.

What is plastisol in fishing lures?

Plastisol is a liquid suspension of PVC (polyvinyl chloride) resin particles in plasticizer. When heated to approximately 320–350°F, the PVC particles absorb the plasticizer and fuse into a homogeneous, flexible solid. After cooling, the material retains its shape and becomes the finished soft plastic fishing lure.

What makes one soft plastic bait softer than another?

Softness depends on plasticizer ratio, PVC resin characteristics, additive loading, and processing quality. Higher plasticizer levels reduce stiffness, while resin particle size and fusion control affect elasticity and recovery. Small formulation differences change flexibility, density, and action, which is why some baits feel supple and responsive while others feel stiff or rubbery.

Key Takeaway

Soft plastics are engineered systems built from:

• PVC resin (structure)

• Plasticizer (flexibility)

• Controlled additives (performance modifiers)

The difference is not brand magic. It is formulation control.

Understanding the material system is only the first step. How those material choices are applied in actual lure design determines how a bait performs in real fishing conditions.

To see how these material principles translate into real-world trout and panfish designs, we outline how we design our soft plastics for trout and panfish.

In Part 2, we break down how heating and fusion affect the final performance of plastisol — and why improper processing can ruin even a perfect soft plastic fishing lure formula.