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Preparation of Surfaces
We have an expression that painting is 90% preparation and 10% decoration. Never has this statement been so true as in the case of graining and marbling.
It is necessary for a properly finished job to begin with a substrate as smooth as a baby's behind, free of irregularities, cracks, pit holes, indention's, etc. The reason for this is that when you are graining, the graining liquid will pool in these areas and being colored, will look unsightly. So it will be best to spend extra time to do it right.
If the surface is beyond help, then stripping the old paint off would be the only solution. Virtually any surface that can be painted can be grained as well. Proper prime coats, whether wood or metal, are essential. Spackling imperfections are necessary. Do not apply spackle just directly over an unprimed substrate. For example, let's take an old, badly abused door. Let's say it has been varnished several times and beat to a pulp. First, we need to clean it thoroughly to remove dirt and grease using a non-oily solvent like Xylene or Naphtha. Sand the door thoroughly, then apply a light coat of white pigmented shellac if you are planning a paint-varnish system. If you are planning a lacquer system a coat of white flat lacquer undercoater dusted on very carefully to avoid lifting. It is necessary to find the right primer to adhere to the varnish or lacquer.
Should you decide to strip off the old varnish, you can prime the door, after sanding, with two coats of oil base undercoater, sanding in between coats. On surfaces previously grained, it is just like those which have been varnished because they have been varnished over their graining. It is essential to get your primer on smooth, free of brush marks. This may require the use of leveling agents such as Penetrol if hand brushing, or the correct thinners if spraying. After the primer is on we can begin to prepare our work. Having the primer on helps you see the imperfections in our substrate much better, as well as provide better adhesion to the varnish or paint below.
Spackle all imperfections with a dense spackle rather than some which are light weight, quick drying, or easily sanded. We have found Min it-Patch from MAB to be very adequate for this purpose. When graining over a metallic surface, such as an elevator door, "bondo" or body filler should be used to assure proper hardness and adhesion. If you do metallic surfaces such as these, it is best to treat them as you would a car, using the same primers, body fillers, and spot putty for preparations.
In our quest for a smooth substrate it is essential to check over our work several times for imperfections, preferably with a handheld drop light of about 50 watts. Holding this light next to our work shows shadows revealing imperfections in our work. This is by far the best way to check for problem areas. We have also found that a plastic squeegee (bought at auto body suppliers) is best to apply your spackle, bondo, or spot putty. The spackle will shrink so it might be necessary to apply two or three coats to fill the problem area. Proper sanding of these areas are essential. It would be wise to avoid the use of a belt sander. They are just too hard to control and take it off too fast.
A conventional orbital sander is best, followed by hand sanding with a block on flat areas and by hand on curved or irregular areas. Be careful to sand thoroughly so as not to leave any ridges. Use about 100 grit sandpaper for your preliminary sanding and finish with 200 or 220 grit.
After you have checked and rechecked your work and have determined it to be free of imperfections, you are ready to apply a second coat of primer. Remember to seal all your patched areas before your ground coat. You only need to seal the areas where you have spackled. Recheck your work again and then sand your entire work with 220 grit. Keep in mind, when you apply your ground coat over the primer, if the primer is not smooth. When you sand your ground coat before graining, little white spots will appear where the imperfections or junk in your paint was. I cannot emphasized enough how important it is to begin and end with smooth surfaces, continually sanding between coats at least lightly. Be sure to strain all paints thoroughly from your primers to your final coat of varnish for smooth work. You are now ready to apply your ground or base coat.
GROUND COATS OR BASE COATS
The most important factor for successful imitation of wood is that of the ground color, to which the graining applied, it should be similar to the color of the wood which we desire to represent. Often too little attention is paid to this detail of the work. I have been called in many times in the past to grain jobs where they tell me. The ground coat has already been applied, and they would like, dark oak graining. When I get there I find a light oak ground color much to my dismay. I have seen much work rendered ineffectively by a ground color unsuited to the wood being represented.
The most important rule for ground colors applies to all types of woods. The color of the ground should be similar in tone and, if anything, slightly lighter than the lightest color seen in the wood being rendered. NOT the unfinished wood, but the wood filled, sealed, shellacked or varnished and finished.
We are now ready to apply our ground coat. Let us dismiss the idea of using latex or water based paints for ground coats for beginners. It just does not work very well. It is difficult to get it on smoothly and it does not sand. It is best to avoid completely. Find some oil base eggshell enamel or oil base flat enamel (even oil base gloss enamel will work if sanded well to dull the sheen). Remember the smoother the paint applied, the better your graining will look. Spraying your ground color is by far the best way to achieve a smooth finish. If you are using a lacquer system, use a flat ground color if you plan to use water colors over it. If you are using oil colors over your ground coat, a satin sheen is most desirable. (Using a lacquer system has advantages when it is necessary to finish the job quickly and spraying is feasible.) This not to say that you cannot use latex based products for base coats because I have used them with success but it is much easier to work with the oil products.
If time is not too important, a higher quality job is done by using oil based eggshell enamel and a varnish system. If you put on a water color antique, then use a flat enamel as the water color takes better to the flat paint. Before application of your ground coat, make sure you strain your paint thoroughly as to provide a smooth finish. This coat should be on thick to fill any small void or scratches still there. Avoid runs, but put it on thick. For this reason it is advisable to use a heavy bodied eggshell enamel. When spraying the ground coat is not possible, use an eggshell enamel that flows out well to avoid brush marks. Use if possible, a combination ox hair and bristle hair brush for optimum results. If one coat is not adequate use a second.
The color of the ground coat is, of course, dependent upon the type of wood desired. Normally the color is a bit lighter than the lightest portion of the wood you want to represent. For example, in a light oak colored wood the ground color would be a light beige color. Only painstaking practice and trial and error will suffice to get this color picking down. Keep in mind that this ground color is followed normally (as in oak) by first an antique to provide texture, second the actual graining, and third the toner, then two or three coats of varnish. It's better to be a bit light and "swing it in" with slightly tinted varnish. See the specific section on the desired wood you wish to grain for more information on the exact color of the ground. Remember, sand lightly after every step except for actual graining.
Important note: More often than not, if you are going over your oil base ground coat with an oil glaze, one day or overnight will not be adequate time for your ground coat to dry. Even with the addition of Japan Drier results are marginal. It is best to let your ground coat (if an oil base enamel) dry through the weekend if possible, to avoid lifting or dissolving by the oil glaze. If lacquer is used, it is not a problem.
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