What substance is commonly used as a solvent in shellac finishes?

Shellac is a traditional finish that is made from natural resins secreted by the lac bug. To dissolve shellac and create a workable finish, a solvent is required, and the most commonly used solvent for shellac is alcohol, specifically ethyl alcohol or denatured alcohol. Alcohol effectively dissolves the resin, allowing it to be applied to wood surfaces smoothly.

The use of alcohol as a solvent is advantageous because it evaporates quickly, which helps in achieving a fast-drying finish. Additionally, it provides good adhesion characteristics and enhances the clarity of the finish, allowing the natural beauty of the wood to shine through.

Other options such as water, oil, and acetone do not effectively serve as solvents for shellac finishes. Water can cause shellac to emulsify and lose its film-forming properties, while oil could lead to a poor finish and longer drying times. Acetone, on the other hand, is too strong and can alter the properties of shellac, potentially leading to unwanted effects on the final finish quality. Thus, alcohol remains the preferred and correct choice for dissolving shellac in woodworking applications.