Guide to Working with Plastics: A Wealth of Fillers and Paints--A New Generation of Buffered Sealants

Polymers, the stuff of plastic resins, have infiltrated the manufacture of such age-old sealing agents as mortars, grouts and caulks—in some cases a polymer fortifies existing formulas, and in others it re places the older material altogether. Most modern caulks are made completely of plastics; mortars and grouts are still largely cement, sand and water. But modified mortars and grouts supplement the standard v and are useful where greater strength is needed.

The toughest of the fortified mortars is one that has an epoxy added—it is about three times stronger than conventional mortar. It’s also more resistant to the elements, and it adheres to wood, a property that permits stone flooring to be laid over a wooden subfloor rather than over a concrete slab. For patching concrete, epoxy-fortified mortar is superior to conventional mortar.

Epoxy-fortified mortar has three ingredients—a liquid resin, a liquid hardener and a cement-sand powder; all are avail able from building-supply and hardware stores. The two epoxy components are mixed first, then the mortar powder is added, usually in a ratio of about 1 quart of epoxy mix to 13 pounds of powder. The epoxy components come in 1-pint to 5-gallon containers.

Working with epoxy mortars requires the same tools as for regular mortar—a mixing bucket, a stirrer and a notched trowel—with the addition of rubber gloves to spare your hands possible irritation from the epoxy. The working methods are also the same, except that epoxy mortars set up faster than regular mortars. Mixed, they have a pot life of about three hours; spread, the mortar must be topped by brick or stone in about 20 minutes, or a skin will form across the top, rendering further cementing impossible.

Latex, another plastic resin added to mortar, yields a product about twice as strong as conventional mortar and mid way in cost between epoxy mortar and the conventional type. It’s noted for its resistance to moisture and to cracking caused by vibration. But unlike epoxy mortar, it does not adhere to wood. Sold in two parts—a liquid resin and a cement-sand powder—latex mortar is mixed and applied in the same way as epoxy mortar.

Latex additives are also used to fortify grout, the cement mixture troweled between tiles or stone, giving this product advantages that latex gives to mortar: greater strength and resistance to water. Translated into practical terms, this means fewer repairs and easier cleaning.

Commonly available in tile stores, although at a premium price, latex grout comes in two parts— liquid latex and cement powder—to be mixed in the proportion of roughly 26 ounces of latex to 10 pounds of powder. No more difficult to use than regular grout and calling for no extra tools, the mixture—like other plastic sealants—must be applied faster than conventional grout.

Plastic caulks, like their predecessors, the linseed-oil-base colloids, are avail able in tube and rope form, as well as in cans and caulking-gun cartridges. Applied to outside surfaces, especially places where dissimilar materials meet, these modern caulks do a better job of keeping out weather and insects.

Of the many caulks on the market, the most common (chart) are acrylic latex, solvent acrylic, butyl, polysulfide, polyurethane and silicone. The two acrylic caulks are for indoor and outdoor work respectively. The butyl will last longer than these outdoors, and more durable still are the last three, called elastomers for their rubber-like properties. Unfortunately, some of these elastomers will shed paints that cannot flex readily under temperature changes, but to make painting unnecessary, they come ready-made in common colors.

Working with Resin-fortified Materials

114---

---Using resin-impregnated materials. Clean the work area and assemble the tools and materials you need. Mix the mortar or grout according to the manufacturer’s instructions (here, the mortar is an epoxy type), and trowel out enough to last for about 10 minutes of work. For mortar, spread the mixture with a notched trowel held at a 45° angle (above, left). For grout, spread the mixture with a rubber float held at a 45° angle, forcing the grout into the spaces between the tiles (above, right). Use a finger to press grout into corners. Let the grout dry for 5 to 10 minutes, then wipe the tile with a clean, wet sponge. Rinse the sponge often in a bucket of water, but don’t pour the grout-filled water in a sink or bathtub; the grout may clog the drain. Let the tile surface dry until a haze appears, then buff the tile with a crumpled piece of nylon.

--Ranking caulks. The chart above shows common kinds of plastic caulks along with their main distinguishing features. Listed horizontally, the caulks are rated for durability and adhesion, and for the length of time they take to lose their initial stickiness, which indicates how long they stay workable. Also given with each listing is the solvent needed to smooth or clean the caulk; the final column shows special factors governing the use of a given caulk. All the caulks are available in colors, all but the latex caulks are suit able for outdoor work and, in general, the longer lasting the caulk, the higher its price. The sol vents abbreviated are trichloroethylene (TCE).and methyl ethyl ketone (MEK).

A Simplified Seal Done with a Caulking Gun

Applying the caulk the right way. Before be ginning the caulking operation, check the condition of the surface to be caulked; except when you are using latex caulk, which can be applied on a damp surface, the area should be clean and dry. Also check the cartridge label for special instructions covering such situations as caulking in cold weather or over unprimed surfaces. Then prepare the cartridge: Cut off the nozzle at a 45° angle and puncture the inner seal by pushing a long nail into the nozzle. Hold the cartridge against the work at a 45° angle and pull it toward you, pumping the trigger, Make the bead of caulk overlap both edges of the crack. Smooth the bead with a solvent-soaked cloth.

TABLE OF: Common Caulks and How to Use Them

Durability | Adhesion | Tack-free | Solvent | Comments

Acrylic Latex | 2 to 10 years | Good | 1/4 to 1/2 hour | Water | Not recommended for outdoor use or on metals

Solvent acrylic | 2 to 10 years | Good | ¼ to ½ hour | Toluene | Satisfactory on most surfaces; good for around doors and windows

Butyl | 7 to 10 years | Excellent | ½ to 1½ hours | Naphtha, paint thinner | For use mainly on masonry; high moisture resistance; shrinks slightly as it cures; principal color gray

Polysulfide | 20 years | Excellent | 24 to 72 hours | Toluene, ICE, MEK | Requires recommended primer on masonry; not recommended for use on glass; available in aluminum color for use on storm windows

Polyurethane | 20 years | Excellent | 24 hours | Toluene, paint thinner, MEK | Relatively easy to apply; requires recommended primer on metal

Silicone| 20 years and up | Excellent | 1 hour | Naphtha, toluene, xylol, paint thinner | Excellent around bathtubs and outdoors on glass and metal; requires primer on masonry