- Home Improvement
How to Paint Your House (Part Two) Preparing Your Surfaces
Necessary Steps to Take Before Painting
Most coating problems and paint failures (85-90%) are due to improper surface preparation. While the glamor of painting is the final application, the foundation is how the surface is prepared according to the conditions present. A surface must be correctly assessed and then addressed before a quality paint job can be completed. Naturally the surface should be clean and dry, yet there is a lot more too it when you are dealing with various conditions.
Before Staining and Varnishing
BEFORE PIGMENTED OIL STAINS
For a more uniform color, a thin sealer is recommended when applying the stains on bare wood. This is especially important on soft woods like pine. Since the cross-cut wood grain absorbs far more stain than other surfaces, a linseed oil or clear shellac is recommended to cut the edges before staining. Wipe the surface with a clean cloth soaked in mineral spirits, then wipe it with a tack cloth. Oil stains are usually brushed on or wiped on with a rag. Applied properly they will leave no brush or lap marks. While the stains are still wet it is easier to control the depth of pigmentation. Wipe off excess stain with a clean rag about five or ten minutes after applying it. If a section gets too dark, simply rub it with a solvent that is similar to the solvent in the stain, or, once the stain dries it can be sanded to lighten the color .
BEFORE STAINING EXTERIOR SURFACES
Prepare the surface carefully. Caulk cracks around windows, door frames, etc. Nail down loose siding if necessary . Make sure the surface is dry, clean and free of grease and mildew. In the case of new construction, apply the stain to bare wood as soon as possible to prevent discoloration from the weather. When applying Solid Color Stains over previously stained or painted surfaces, remove dust, dirt, peeling paint and chalk deposits with siding cleaner and scraper. If a Solid Color Stain is to be used over bare
redwood or cedar, first apply a professionally recommended primer to avoid tannic acid bleeding through. In using a Semi-Transparent stain on old surfaces, remove the old finish by sanding or scraping down to the bare wood.
BEFORE APPLYING SHELLAC
Since most shellac has a shelf life of 18-24 months it is always good to check the expiration dates before purchasing. Almost always sold premixed it may be too thick for some applications, if so, dilute it. Follow the same preparation techniques used with varnishes.
BEFORE APPLYING VARNISH
It should be noted that in all cases labels on the products used should be read carefully since the manufacturer will have recommendations as to surface preparation, application and other valuable information regarding compatibility and incompatibility with other coating products. Many varnishes can be applied over many paints and stains. Over high-gloss coats a light sanding is recommended and wiping it with a tack cloth will help the varnish to adhere to the existing coating. Most urethanes can not be applied over or under shellac. Also, they peel, remain soft and/or blush if applied over sealers that contain shellac or polyvinyl alcohol. While some urethanes will adhere to lacquers on top of others they may "blush" and develop white spots. There are certain urethanes that should not be applied over fillers with stearates because the stearate will act like soap and cause adhesion problems .
Varnishes must be applied to clean, dust-free surfaces in a dust-free area, using clean application tools such as brushes, rollers, pads or sprayers. Always stir, not shake, cans of varnish.
On floors and stairs two coats of urethane should be recommended for maximum durability of the film; one thin coat followed by one heavy coat. Some Urethanes require one or two days drying time between coats. Some alkyds also require a day or two. There are other varnishes that can be recoated in six to eight hours and cure completely overnight. Make sure and read the label.
Varnishes are hard to touch up - a new coat of varnish may form a shiny patch on the previous coat.
Before applying to Varnished surfaces in Good Condition (not cracked or peeling): To refinish the surface with another clear coat, remove all dirt, grease, wax and scuff marks. Use a paint thinner or a professionally recommended stripper. Rinse and dry completely. Sand the surface lightly and remove dust with a tack cloth. Finish with a coat of clear varnish.
Before applying to Varnished surfaces in Poor Condition or to apply a stain: Remove all of the old finish completely ....
Refinishing Furniture: Remove all hardware and place in a horizontal position. Apply professional paint & varnish remover with a brush (use rubber gloves to protect hands and work in a well ventilated room). Let the remover stand until the old finish wrinkles or softens enough to be removed with a putty knife or steel wool. Take care not to gouge the surface. Repeat the process as often as necessary. Then clean the surface with steel wool dipped in paint thinner, rinsing frequently. Wipe surface dry and let stand overnight before sanding. Sand with the grain only - use medium\course paper or steel wool first and finer paper or steel wool later. Remove all sanding dust with a tack cloth, prior to varnishing.
Refinish Floors: Remove old varnish (if necessary) then remove all moldings, furniture, rugs drapes, pictures, etc. Use a power floor sander and power edger to sand off the old finish. Pick up all Sanding dust with a vacuum. Go over the floor with a tack cloth to make sure it is completely "dust-free."
Surfaces Guide From Aluminum to Wood
Make sure that all mill scale, rust chips, flakes and blisters are removed with a scrape, sandpaper or wire brush. If the project is an exterior one, sand blasting may be the answer. Chemical products such as rust removers and rust converters may also be helpful. It is also a good idea to use a detergent to clean grease and dirt from the surface.
BLEEDING KNOTS & WOOD
Bleeding knots on the exterior of surfaces will require treatment before paint can be applied. First, the knot should be sanded down to remove any existing coating and seal. White-pigmented shellac/four-pound orange shellac, knot sealer, stain killer or prime sealer with stain killing properties are recommended to seal the knot. Most knot sealers and stain killers are shellac-based, since shellac is the only product available that effectively seals the bleed for an extended period of time. White-pigmented shellac is effective on 90% of all wood and wood knots - the stubborn ones may require four-pound orange shellac. The products listed below may be of benefit in sealing bleeding wood knots:
Knot Sealer Scrapers
Power Sanders Shellac
Primer-Sealer Stain Killer
Sanding Block Steel Wool
"Normal" chalking exists if the paint coat is still securely attached to the substrate, if it is uniform and not excessive. Chalking is not excessive if, upon rubbing it slightly, a dull luster is produced. Washing alone may take care of normal chalking. Some alkyd primers and specialized latex primers can also "fix" the chalk so that a new coat of paint will adhere. These primers may be labeled "adhesion primer." If chalking is excessive the old paint should be removed completely.
It is recommended that a bleach wash or clear water rinse (with a high pressure sprayer for exteriors) should be done. The bleach will kill any mildew, mold and algae on the surface. If the concrete has been penetrated by oils or gasoline (e.g. concrete floors) they will be virtually impossible to paint since it is so difficult to clean such surfaces well enough to make the paint stick. Acid etching with 5%-10% hydrochloric (muriatic) acid is usually required. It should be applied liberally and then rinsed thoroughly. After cleaning, an acrylic or latex block filler can be used. For a waterproof surface, follow with a hydrophilic coating. If there is an existing coating consult a dealer, since not all coatings are compatible.
As previously stated, Copper is not usually coated, however, some objects may have a factory applied lacquer coating which should be removed with a lacquer remover or steel wool and metal polish before recoating. A protective coating of lacquer will allow the original metal to show through, create a luster and protect the metal against tarnishing and abrasions.
CRACKED, CHIPPING PAINTED SURFACES:
Ideally any old paint should be completely removed, but as we all know that isn't generally feasible, besides there is no need to remove paint that is still firmly attached to the substrate. However, if these areas are not properly dealt with, an uneven surface
will result. If the paint is loose enough, a power washer can be used to blast it off. Scraping, wire brushing, chemical paint remover, sanding, can all be employed in removing old paint. After the loose paint is removed cracks should be filled with putty, and the edges of the remaining paint and any rough surfaces should be feathered and sanded smooth.
Warning: If old paint contains lead, there are federal regulations regarding removal
and disposal. Most likely there are also state and local agencies with additional health, safety and environmental regulations regarding lead paint. If lead paint is present local government authorities should be contacted for specific instructions.
If the door is raw wood, treat it as a flat wood surface. If previously coated look under condition of the wood. If it is metal refer to the type of metal surface.
EXPOSED NAILS & HARDWARE:
Hardware should be removed rather than trying to paint around it. This includes; electrical outlet covers, picture hangers, light switch covers, sconces, etc. If in the preparing of the surface, repairs are made which results in exposed nails, screws or other type of fastener, seal the metal to keep it from discoloring the top coat. Most alkyds will not adhere long when applied directly to galvanized metal. Sink the nails below the surface of the wood, then fill the dent with putty. Sand the putty to make the surface smooth, then prime. If the nails are rusted, sand the nail heads and seal them with a sealer, primer-sealer or primer that contains rust inhibitors; then sink them as with new nails, and follow the above procedures.
There are two problem areas with this type of metal. First there are large amounts of oil and greasy deposits left over from the manufacturing process. Second the Zinc coating applied to the base metal is soft and greasy by nature. The easiest way of preparing galvanized metal is to "weather" it, leave it out in the weather for six months or so before painting. This allows the oily residues to turn to soap and wash away. It also allows the zinc to oxidize and roughen the surface. Since this is not always possible a second technique is to wipe and wash the metal clean of all oily deposits and then chemically etch the zinc surface with a commercial galvanized pretreatment. These contain wetting agents and an acid and should be used according to label directions. Some coating experts recommend washing the surface with vinegar. These pretreatments usually require rinsing the surface to remove excess reactants before being coated. A specially formulated solvent based or latex primer should be used, then the finish coat can be applied.
The fence must be made ready to hold paint. At the very least it should be thoroughly washed down. Paint will not stick if there is any dirt, mildew and/or algae. A garden sprayer can be loaded up with a gallon of warm water, a pint of household bleach and a cup of trisodium phosphate (TSP) or strong cleaner. Spray this onto the fence and let it set for ten minutes . Scrub the fence with a stiff brush then rinse. Make sure the fence is dry before painting. Usually it is best to use a sprayer when coating a fence since there are many hard to reach faces and edges. If there is a large area to be covered the best tool is a high pressure airless unit that will take the paint right from the can. Ordinarily, regular house paints work well for fences, and they should be primed especially if the wood is bare. If mildew is a problem, latex paint will outperform oil-base. Opaque stains can also be used and are less likely to peel, crack or blister, but will need recoating more than paint.
Before painting clean the fence with a sponge soaked in paint thinner. This wash is a good idea even for new fences since they may be coated with an oily film that can interfere with adhesion. If the fence is old and rusty, scrub it with a wire brush or wire wheel of an electric drill before washing with paint thinner.
These fences are so open it is a messy waste of time to spray them . The best tool for the job is a long-napped roller. Get one with nap about an inch long, this will be able to reach into and around the wires and make quick work out of an otherwise tedious job.
The Paint: Any good paint formulated for metal will do the job. Many people use aluminum paint on chain-link fences, but if the paint needs to be less conspicuous, a darker color would be better.
For new gypsum board use an inexpensive blend or latex wall sealer. Over existing paint, sand the repaired areas and spot-prime. Do not use an alkyd.
INTERIOR FLAT WALL:
The idea is to create a smooth surface so that the new coating will bond securely and look attractive, so it is essential that all cracks, holes, dents, gouges, open or uneven
joints, exposed nails, or other hardware are patched, repaired or covered. After the repair, apply a sealer, primer or primer-sealer to the repaired areas. It is crucial that these areas are sealed since they are more porous than the surrounding wall . If the materials used in the repairs contain alkalies the sections must be primed with latex primer.
Before painting a masonry surface it must be free of dirt, oil, powdery dust and loose chalk. It should also be rough enough to ensure good adhesion. New, or unaged surfaces offer some challenges due to unbound moisture left over from the original mixing, a high degree of alkalinity and efflorescence in the form of a white, crusty material that can come to the surface. For masonry less than a year old an alkali resistant sealer, conditioner or all acrylic latex paint should first be applied. These tend to resist alkaline attack. Still, it is preferable to wait 30 days before coating new masonry . Previously painted masonry should be bleach-washed, brushed and then rinsed with clear water. The bleach will kill any mildew, mold and algae. If the masonry has started to crumble and needs repair, use a cement patch and then a block filler. If the coating or surface is exposed to extreme temperature changes, fill the holes and cracks with a flexible caulk. It is a good idea to apply a clear masonry sealer after the repairs are made and before the finish coat. Just as with concrete, masonry surfaces penetrated by oils or gasoline are virtually impossible to paint because they are difficult to clean well enough to make the paint stick . The same method of acid etching used on concrete, can be applied here. Make sure that the surface is rinsed thoroughl y before painting.
It is imperative that before coating a metal surface all mill scale, rust chips, flakes and blisters be removed by scraping, sanding or wire brushing. If the surface is an exterior one a sand blaster might be handy. Chemical products such as rust removers and rust converters can also be helpful. To clean grease and dirt from the surface use a coarse cloth dipped in mineral spirits.
Scrubbing affected surfaces with a bleach solution is the best approach because power spraying with water alone will not remove deeply embedded mildew and mold from wood. It is not advisable to use TSP (in those areas of the country that still allow it to be sold as a general cleaning agent), since the phosphate in TSP is a fertilizer and encourages the growth of mildew and mold .
These are individual pieces of wood that make up door frames, window frames, window sills, etc. In older homes that have settled the joints are uneven and rough . Prior to painting all open or uneven joints should be filled, masked and prepared using one or more of the following products ; caulk, caulk gun, clamps, glue, power sander, putty knife, sanding block , sandpaper, scrapers, steel wool.
* See Wallpaper. **Also see cracked, chipping paint
When used in patching and filling holes and especially if an alkyd/oil based paint is being applied, it is crucial to first use an alkaline-resistant primer.
If siding is wood and warped, split or broken, replace and then treat as New Wood. For aluminum see section on aluminum.
SHAKES AND SHINGLES :
New shakes and shingles are usually coated at the factory with a clear stain or water repellent both of which contain wax. It is usually easier for an oil-based paint to bond with the surface if a coating, other than the stain, is applied. Old shakes and shingles that are split, warped or broken should be replaced. Warning: Do not paint shingles treated with creosote for eight years.
Generally a new surface it can be treated like gypsum board or you can refer to INTERIOR FLAT WALL on pg..
Steel will corrode and oxidize if exposed to water and oxygen. Seal out the oxygen and/or water with corrosion-resistant paints. Be sure and remove all mill scale, rust, chips, flakes and blisters as discussed in METAL, Also See Galvanized Steel.
You can paint over wallpaper IF there is just one layer on the wall and the layer is firmly bonded. However, there are two reasons to encourage the removal of wallpaper if the decision has been made to paint. 1. The paint might not adhere to the wallpaper. 2. Colors from the wallpaper might bleed through and discolor the new paint. Beyond that there is also the subject of appearance. Seam lines and even raised patterns will still be visible after wallpaper is painted over. The wallpaper glue will eventually fail and then the paint and the wallpaper will peel off. To remove wallpaper the following tools would be helpful: a box knife, sealer, putty knife, shellac, razor sprayer, scrapers. Steaming is another method that is generally the quickest and easiest way to remove wallpaper. Applying hot steam breaks down and softens the glue making it easy to just pull off the old wallpaper. Once the wallpaper is removed it is essential to also remove the glue residue by washing with a strong detergent or scraping. Some paints will not adhere to the glue, which could break down into soap and also leave raised patterns on the surface.
Repair chipping, peeling paint. Remove all hardware and cover exposed nails. Prepare according to the type and nature of the substrate. Also see open/uneven joints pg._.
Begin preparing the surface by removing any dirt, oil, grease, wax, etc. with soapy water. If mildew is present wipe down the surface with a bleach solution. Rinse thoroughly. If there are imperfections in the wood they can be sanded and spot primed. Take care to seal knots and sap pockets with the appropriate product to prevent bleed-through, see Bleeding Knots pg. _. On bare or scraped wood that is prone to exposure it is a good idea to treat with a water repellent or preservative
before priming. They should dry thoroughly for at least two dry weather days before priming. Once the sealer or preservative is dry, then the primer can be applied over the entire surface to provide a sound base coat.
Wood that has already been painted and weathered will require more involved preparation. First, scrape clean any blistered, flaking or loose paint so that only tight paint remains . "Feather" the old paint where it meets a lower surface, by sanding into the edges. Glossy surfaces should also be sanded to provide a good anchor for the new coat. Second, repair damaged or deteriorating carpentry. Next, wash or wipe the surface clean of dust and paint scrapings with a dry paint brush or clean cloth. If the weathered paint has a chalky surface this should be washed off with soap and water and then rinsed. If there is mildew present clean the surface with a bleach solution rinse and let dry. Finally caulk and fill any joints, seams, cracks, set nail heads, holes or indentations. Window glazing putty has been used but fails quickly without the protection of paint. Better choices are caulks or epoxy-based wood fillers. Make sure all residue is removed, smoothed out and that the surface is clean before primer or paint is applied.
Natural or Clear Finishes
Because these coatings are designed to enhance the natural qualities of the wood, the surface has to be in good shape, without flaws, marks or stains. You cannot just cover over problems. Make sure the surface is clean, dust free and dry before applying the finish of your choice.
It is often said that a building is only as good as its foundation. It is the same for a coating. A good paint job depends upon careful surface preparation. The general rule of thumb for all surface preparation, no matter what the substrate, is that it be clean, sound and free from all material.
We know about the types of coatings and their properties. We are thoroughly familiar with various substrates and their unique characteristics. We have reviewed application methods and techniques and know how to prepare the surface for the best results; we are now ready for the piece de resistance, the icing on the cake. We are ready to paint.