Guide to Polyurethane Finishes

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What You'll Need
Polyurethane finish
Linseed oil
Denatured alcohol
Clean cloths
Rubber gloves
Eye protection
Proper respiration gear
Adequate ventilation in the work area

Polyurethanes are liquid plastic resins that dry to a durable satin or gloss finish. Polyurethane finishes are much more resistant to moisture and spills and moderate heat than traditional varnishes and do not need much protection.

Most manufactured furniture is not polyurethane coated, as it requires considerably more drying time and inter-coat work to apply commercially.


Dust regularly with a soft dry cloth and wipe dry. When needed, wipe with a moist cloth, not wet. This will remove fingerprints and light soil. When dirt or grime has built up, clean with mineral spirits.

Wax or polish can build into an enemy. Remove it with a cloth dampened with mineral spirits. Clean small areas at a time. Wipe each area with a clean cloth before going on to the next. Wear rubber gloves to protect your hands, and dispose of them afterward, or wash in hot suds and air dry. Air-dry cloths used in cleaning to evaporate the solvent before disposing of them.

Test for Existing Finish on Furniture

Rub a Few Drops of Boiled Linseed Oil Into the Wood - If it absorbs, the wood has an oil finish. If it beads up, the wood has a hard finish (continue).

Rub Acetone Over a Spot in a Gentle, Circular Motion - Polyurethane finishes shed acetone like water. Lacquer dissolves in 30 seconds with rubbing. Varnishes and shellacs turn to a sticky, gel-like substance after a minute or two (continue).

Try a Few Drops of Denatured Alcohol - Shellac dissolves quickly in denatured alcohol. Varnish reacts slowly.

Caution: Always, take the greatest care whenever working with or around any type of chemical solvents or agents such as denatured alcohol which is highly toxic if ingested and give off toxic fumes, but especially if burned. At all times use a respirator sufficient to the task at hand per manufacturer's guidelines and keep all potentially hazardous materials well out of the reach of children.

Eye protection can prevent accidental blindness from splashes or spills. Never touch your eyes while working on any similar project with bare or gloved hands that may have residue from solvents, paints, ar other chemical agents. MSDS -- Material Safety Data Sheets for the solvents, resins, finishes, and others listed here can be read at

This has been your guide to polyurethane finishes. Now you can ensure your furniture looks good as new for longer!

This article has been contributed in part by Michigan State University Extension