............ is an example of a drier used in varnish.
Try it first: pick an option, then read the explanation.
The Components of Varnish
Varnish is a simple coating, typically made of three main components. Understanding the role of each component is key to identifying them. These are the Resin (the solid that forms the film), the Solvent (the liquid that dissolves the resin), and the Drier (the catalyst that speeds up the drying process).
Detailed Analysis of the Options
(a) Copal & (c) Mastic
Component Type: Resin.
Function: Copal and Mastic are natural resins derived from trees. They are the solid, film-forming substance in the varnish. When the solvent evaporates, the resin is left behind to create the hard, protective layer. They are the substance *being dissolved*, not the drier.
(b) Litharge
Component Type: Drier.
Function: This is the correct answer. Litharge (Lead(II) oxide) is a metallic salt that acts as a catalyst in oil-based varnishes. It accelerates the oxidation and polymerization of the drying oils (like linseed oil), causing the varnish to dry and harden much faster than it would on its own. It is one of the most common traditional driers used in paints and varnishes.
(d) Turpentine
Component Type: Solvent.
Function: Turpentine is a volatile liquid distilled from pine resin. Its job is to dissolve the solid resin (like Copal or Mastic) to create a liquid varnish that can be easily applied. After application, the turpentine evaporates, leaving the resin film behind. It is the liquid carrier, not the drying agent.
Main Components of Varnish
| Component | Role | Examples |
|---|---|---|
| Drier | Speeds up drying (Catalyst) | Litharge, Lead Acetate, Manganese Dioxide |
| Resin | Forms the solid, protective film | Copal, Mastic, Shellac, Polyurethane |
| Solvent | Dissolves the resin to make it liquid | Turpentine, Alcohol (Spirit), Mineral Spirits |