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Eventually, every old-house restorer gets stuck with removing the mastic adhesive left behind by linoleum. The problem is, many different kinds of mastics have been used over the course of a century, making it difficult to predict their exact ingredients and the methods that might soften them. Even more of a concern is the fact that some of these mastics—and the lining felts that accompany them—used asbestos as a component (some floor tiles are also this mineral). This rules out machine sanding (which clogs the paper anyway) and other operations that will make these materials friable, releasing asbestos fibers into the air and creating a potential health threat. Gummed down by these limitations, the two main tools become a cautious trial-and-error approach and plenty of elbow grease. Consider the following guidelines.

• Note that waterproof glue was applied at the edges and seams of linoleum; a weaker (and often water-soluble) paste anchored centers to the felt layer.
• Start with hot water. Soak the mastic for 20 to 60 minutes or until it is soft enough to be mopped or scraped up (keeping the surface continually wet also limits friability). Adding vinegar or high-strength citrus-based solvents (Limo Sol is one brand) to the water may improve effectiveness. On floors, long-handled garden edgers are a break from scraping with putty knives.
• Try heat or cold where water doesn’t work. Modern mastics and those containing linseed oil may soften with heat from a lamp or hot-air gun. Some readers report freezing mastic with dry ice breaks the bond with the substrate.
• Resort to chemical solvents last. Start with the most innocuous solvent and test in an inconspicuous area before proceeding or increasing strength. Isopropyl alcohol, paint thinner, xylol, lacquer thinner, or paint stripper may yield results. Work with plenty of ventilation and proper safety precautions.