Guide to Working with Plastics: A Wealth of Fillers and Paints--Compound to Patch Holes in Almost Anything

Patching, resealing and recoating are the inevitable by-products of having a home: No household surface takes care of itself. Exterior walls, roofs and walkways will weather, crack and change shape under attacks of wind, rain and temperature fluctuations. Interior walls, ceilings, floors and built-in fixtures submit to nicks, scuffs and regular washings, not to mention an occasional blow severe enough to cause greater damage.

In times past, such household repairs often took more time and effort than they were worth. It was easier to live with the scuffs and cracks than to fix them. When restoration was necessary, it was frequently left to professionals, who possessed the specialized tools and equipment—and the years of practice—needed to do the job well. But plastics have changed all that. Today’s easy-to-use synthetic fillers, caulking compounds, sealants and paints make most kinds of surface repairs and refinishing a simple and economical matter, even for the amateur. The same is true for the use of these materials on new work.

The qualities that set these plastics compounds apart from traditional materials are their superior powers of adhesion and their infinite shapability. True to their name, they can be formulated to respond to virtually any demands made of them.

Troweled-on polyester metal fillers, for example, will bond to irregularly shaped holes and dents, eliminating the need for costly welding. Silicone and polysulfide caulking compounds will remain permanently pliant, outlasting their oil-base predecessors, which in time become brittle. Quick-setting synthetic fillers and coatings can be applied without special tools and are packaged in small quantities for household-sized jobs. One-coat synthetic-rubber waterproofing emulsion eliminates the need for expensive layer-over-layer built-up. roofing. Fast-curing epoxy mortars and grouts are far stronger than conventional cement and plaster, and new plastic paints and varnishes cover any surface you are likely to want to finish or refinish. There is even an aquatic epoxy paint that goes on underwater, for refurbishing swimming pools.

Properly applied, most of these synthetic fillers and paints produce surfaces more durable than the natural materials they cover. But when they are used to repair leaks and cracks, more than resurfacing may be required. Sometimes there are serious structural defects that must first be diagnosed and remedied. The success of the job will also depend on choosing the right coating, one that is compatible with the surface beneath, and on preparing that surface properly. These important preliminaries are discussed in this chapter, along with the techniques for applying the new plastic coatings.

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---Convoluted cover-up. Colorless epoxy, called liquid glass, is swirled over a butcher-block table- top, protecting its surface while allowing the beauty of the grain to shine through. The pourable plastic, roughly the consistency of molasses, will be smoothed with the edge of a plastic- covered playing card to form a moisture-proof, scratch-proof seal 1/8 inch thick. With successive applications, the coating can be increased to 1/4 inch without altering the color or clarity of the material that lies underneath.

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Compounds to Patch Holes in Almost Anything

Plastic filling compounds are used to patch holes in everything from teeth to auto fenders. Strong, fast-setting and resistant to water and chemicals, they are ideal for a wide range of repairs around the home. Whether the job calls for filling a gouge in a kitchen countertop, patching a small hole in a water tank or shaping a replacement for a broken corner of a lawn chair, the right plastic filler and application technique can produce a nearly undetectable repair.

The polyester or epoxy resins that are the base for such plastic filling com pounds as wood putty or metal paste can be used in their clear form or mixed with filler materials and pigments to match almost any surface. The choice between epoxy and polyester should be based on the job at hand. Epoxies are more expensive, but they are stronger, adhere better to many surfaces, and offer greater resistance to heat and corrosive chemicals. If these properties are essential, a polyester resin is usually sufficient; polyesters match epoxies in water resistance, are more tolerant of mixing errors, and cure more quickly. Problems of polyester adhesion can usually be overcome by the simple process of roughening the surface or drilling anchor holes.

Both polyester and epoxy filling com pounds are available ready-mixed or in multiple-component products. A ready-mixed filler, such as the familiar plastic wood putty, can be used directly from the tube or can; the resin, hardener, filler and color are already blended. Most such ready-mixed compounds are sold in small quantities and are practical for touch-up work or small repairs, although they are more expensive per ounce than multiple- component fillers.

The parts of a multiple-component filler must be precisely measured and mixed, following the same procedures used for mixing casting plastics. With some of these products, you add the hardener to factory-mixed resin and filler; with others, you add a factory- mixed paste of hardener and filler to the liquid resin. If the hardener and filler are in paste form, mix the paste first with a small quantity of resin to liquefy it and 3 prevent lumps from forming when the rest of the resin is added.

Some products require you to mix fillers and pigments with the resin before you add the hardener. Because of the increased potential for error with such a product, you should make trial mixtures before you mix the batch you will use on your repair. Pay particular attention to the proportion of filler material to resin. Too little filler will result in excessive shrinkage as the mixture cures; too much filler will make the mixture crumbly and reduce its adhesion.

Filling compounds can be matched in color or other characteristics to a wide variety of surfaces by the addition of appropriate filler material. Metal powders, for example, can be used for cosmetic repairs as well as in applications where resistance to stress or friction is required. An iron filler is the one that offers the best resistance to heat or impact, where as an aluminum filler is preferable if the repair will be subject to friction. Graphite powder added to a filler improves its sliding properties.

Nonmetallic filler materials are also available, including ceramic powders, chopped glass fiber, and powdered stone. Glass fiber is an all-purpose filler that is also a strong reinforcement, which makes it useful for sheet-metal repairs. Since it’s water-resistant when cured, it’s well suited for repairing rust holes on water tanks, gutters, steel panels, or even cars. Thinned with acetone to the consistency of paint, glass fiber can also be used to prime bare metal before further repairs are made with chopped glass or other filler.

Fillers of powdered ceramic, which have good insulating properties, are the best to use for repairs where heat or electricity is present. Such ceramic fillers can be readily tinted by adding colored powders, which are available at most paint or hobby stores.

For patching and repairing wood, many ready-mixed compounds are available in a variety of wood colors. These tinted fillers cannot be further colored with stain; however, they can be re-tinted be fore they are applied to achieve the exact color desired, or touched up with an oil- base paint after they have cured. You can avoid the necessity for this chore by mixing your own filler, using a polyester resin base and fine sawdust from the wood you are using. If you intend to stain such a mixture at the same time you are staining the surrounding wood, use a high concentration of sawdust in the filler, and brush the hardened patch with acetone to expose as much of the sawdust as possible prior to staining.

You will need a kitchen scale to mea sure ingredients by weight, or a glass measuring cup if the ingredients are to be measured by volume. Use disposable cups and spatulas for mixing, or use glass and metal utensils that can be cleaned with acetone to prevent impurities from getting in the filler. Clean paintbrushes with acetone between applications, or use very cheap brushes and discard them after they have been used.

An electric drill is handy when you are preparing a surface for repairs. Fitted with a sanding disk, it can be used to remove paint or corrosion quickly; with a burr bit, it can be used to grind a feathered edge around a hole. Masking tape and paraffin are needed to contain the filler and to protect the surrounding surface from solvents.

To put a smooth surface on the filler, you will need to cover it with a sheet of clear plastic household wrap, which won’t stick to the filler. To polish a finished repair, use a buffing disk with a plastic-polishing compound.

==Tips on Safe Handling==

Because almost all of the chemicals in plastic fillers are volatile and some what caustic, you must take care to ensure adequate ventilation and avoid open flames. Use plastic gloves and protective eye goggles to prevent accidental contact with the materials. If any resin does get on your skin, use the recommended solvent to remove it, then wash the affected area immediately with soap and water. Before opening any of the filler containers, read the manufacturer’s safety information and familiarize yourself with the remedies prescribed.

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A Nearly Invisible Patch for a Small Hole

1. Preparing the hole. With a burr attachment on an electric drill, feather the edge of the hole at a shallow angle to a distance of ¾ inch (inset). Use the drill’s cooling-fan exhaust to blow loose particles and dust from the hole.

2. Making a wax dam. Shape a bit of paraffin wax with your fingers to build a 1/8-inch dam around the hole, slightly outside the feathered edge. Don’t let the wax touch any part of the hole; it would keep the filler from sticking.

3. Filling the hole. Using a shallow dish, mix enough filler to fill the hole, then use the mixing spatula to drip filler into the hole. Tamp the filler with the spatula to force out any air bubbles. Then add filler until it’s about 1/16 inch above the undamaged part of the surface.

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4. Trimming off the excess. When the plastic filler has partially hardened (usually in about five minutes). Use a sharp, wide-bladed putty knife or a single-edged razor blade in a holder to shear away the wax dam and the excess filler flush with the surface. Avoid gouging the filler or the wood beside it with the corner of the blade.

Discard any leftover filler and clean the tools with acetone. Mix a small batch of fresh filler.

5. Finishing the filler. Drip a small amount of filler onto the repair and cover it with a piece of clear plastic wrap. Spread the filler evenly by lightly smoothing it with a single-edged razor blade drawn across the film. Remove the film and allow the filler to cure for two to five hours, according to the manufacturer’s instructions.

6. Buffing the repair. After lightly hand-sanding the patch with 400-grit emery paper, spread rubbing compound on a buffing attachment for an electric drill and buff the patch, using light pres sure and a circular motion. Continue until the patch area blends into the surrounding surface.

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Stopping a Crack and Sealing It with Filler

1. Drilling to stop the crack. Drill a hole ¼-inch in diameter through the cracked plastic surface to relieve the tension that is creating the crack. When you do this, use the end of the crack as the center point of the hole.

2. Widening the crack for filler. Use a small tri angular file to enlarge and deepen the crack, making a V-shaped groove at least 1/8 inch deep. Feather the edges of the grooves slightly, and clean out all loose particles and dust. Cover the undamaged surface with masking tape extending right to the feathered edges.

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3. Fling the crack. Using a shallow dish, mix enough plastic filler to fill up the filed groove, then apply the filler with a putty knife, working across the groove. Build up the filler about ‘A6 inch higher than the original surface. When the filler has partially hardened, remove the masking tape and complete the repair as shown in Steps 4 to 6.

Anchoring Filler in a Sheet-Metal Dent

1. Stripping paint from the surfaces. Remove paint and other protective coatings from the dam aged surface, using an electric drill fitted with a wire-brush attachment. Using heavy pressure and a slow, sweeping motion, expose shiny metal across the entire damaged area and 1 inch more of the surrounding surface in all directions. Use either detergent and water or alcohol to clean and degrease the stripped metal.

2. Drilling anchor holes. Drill ¼-inch anchor holes about 1 inch apart within the damaged area to offer a good grip for the filler. Paint a thin primer coat of polyester resin overall bare metal.

Cover the area around the primed surface with masking tape. When the primer is no longer tacky, fill the dent with polyester filler (Step 3). Let it cure, then sand it smooth and paint it to match the surrounding surface.

Renewing Stripped Threads with an Anchored Plug

--Preparing the hole. Remove the damaged threads by drilling out the hole with a bit one and a half times the original diameter of the hole. Use a small triangular file (left) to cut several notches in the side of the hole; these notches, which should be at least 1/8 inch deep, will prevent the filler plug from rotating. Clean the hole and degrease it with alcohol, then fill it as shown in Step 3, opposite, using a filler that matches the color of the surface.

Allow the filler to cure completely (this will generally take from about two to five hours), then re-drill the hole through the filler plug to the original diameter. Cut new threads in the new hole with a tapping tool (inset).