Paint technology — in traditional oil paints, linseed oil primarily functions as which ingredient? Select the most appropriate role.

Introduction / Context:
Conventional paints comprise pigment (color/base), vehicle or binder (film-former), thinner/solvent (viscosity adjustment), and small additives like driers. This question tests recognition of linseed oil’s principal role in oil-based paints, a fundamental topic in building materials and finishes.

Given Data / Assumptions:

• We are considering traditional oil paints used on wood, metal, and masonry.
• Linseed oil is a drying oil that oxidatively polymerizes in air.
• Driers are metallic salts (e.g., cobalt, manganese) used in small amounts.

Concept / Approach:
As a drying oil, linseed oil forms a solid film through oxidation and polymerization, binding pigments to the substrate. Therefore, it is the vehicle (binder). Thinners such as turpentine/mineral spirits only adjust viscosity and evaporate; pigments form the base; driers catalyze oxidation but are distinct additives.

Step-by-Step Solution:

Verification / Alternative check:
Standard paint formulation texts list linseed and other drying oils as vehicles, with pigments dispersed within to create the paint body.

Why Other Options Are Wrong:

• Thinner: Solvent only; no film formation.
• Base: Colorant/opacity provider, typically mineral pigments.
• Drier: Metallic soaps/salts; used in minute quantities to accelerate curing.

Common Pitfalls:
Assuming the largest liquid component must be a solvent; in oil paints the binder itself is the major liquid phase.

Final Answer:
Vehicle (binder)