Intarsia
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Visiting museums, exhibitions, art salons, you, obviously, paid attention to plot-decorative compositions made of multi-colored wood. This is a kind of mosaic or applique made of single-layer colored plywood - intarsia.
For intarsia, not only color is of great importance, but also the texture of the wood, which is found in different ways in tree species. Usually, no more than three to four colors inherent in wood are used in intarsia. If some color is missing, then you can tint the plywood with aniline, or even better with natural dyes (oak bark, buckthorn, bulbous plants).
To work in the intarsia technique, you must have a set of tools and equipment. The most useful tool is a knife. You can use a surgical scalpel or straight razor.
If you need to cut through two plywood at once, then use a knife with a long handle, which is supported on the shoulder. A lapping hammer is used to grind and smooth the assembled composition to the base. To clamp the typed pattern, you need: a press, or bar frames and wooden wedges of different thicknesses. The glue is brewed in a glue pot or ordinary tin can, which is placed in another dish (pan), but so that it does not touch the bottom. To cover the base with wood glue, you need to have a hard, wide brush. A plywood base or board is processed with a zinubel (a carpentry tool similar to a plane). If the set is planned to be glued to a wood board, then surface treatment with zinubel is not needed.
For intarsia, you also need a glued paper tape. You can make it yourself. To do this, a sheet of printer paper is lubricated on one side with a not very thick solution of wood glue. Then, when the tape is dry, it is cut into strips 15-20 mm wide. During operation, the tape is moistened with warm water and individual pieces of fitted plywood are glued together.
Having conceived a certain composition, it is imperative to choose its color and tones, remembering that an excess of colors and tones can only impoverish the artistic expressiveness of wood. Therefore, they are usually limited to three to four colors and two to three tones of color. When making a drawing for intarsia, one should avoid small details, trying to achieve the most generalized form possible.
The sketch is performed in a mirror image relative to the conceived composition, and a set of intarsia is produced from the mirror image.
The intarsia set procedure is as follows: pieces of plywood of the desired tone are cut along the contour of the drawing and glued together with glued tape, after which the finished set is applied to the base. First, a drawing is applied to the background using carbon paper; large planes are cut out and plywood inserts of the desired color are fitted in their place. You can qualitatively adjust the part by placing the desired piece of plywood under the base with a cutout. And so that it does not move, it is glued from the back side with adhesive paper to the base, then carefully cut along the contour with a knife. If you have to adjust several parts at the same time, this should be done especially carefully at the joints, and the order of adjusting the parts should be thought out so that there are no more than two butt sides. Cutting out the desired part,it is installed in the prepared place and glued on the back with adhesive paper, wiping the adhesive side with a damp piece of cloth, cotton wool or foam rubber. First, large planes are installed, then smaller ones.
It is very difficult to cut a part along the contour so that it does not chise or crumble. This can be avoided: stick the paper on one side so as to cover the entire plane intended for insertion.
Beginners should be warned against making different turns of the same piece of plywood. After polishing, the plywood can change its tone, appear lighter or darker, so it is better to lay the layers of wood in one direction. This, by the way, will facilitate the processing and cleaning of the finished work glued to the base.
It is better to get around the small details first and stick the work without them. Then, when the work dries up (3-4 hours), carefully cut the part, cover with paper and easily run with a hot iron, and the glue will warm up and become soft. Then the cut out part is easy to select with an awl or knife, and insert the desired piece into the place of the recess.
Having finished the set of intarsia, prepare the base. The basis for intarsia can be plywood, wood board or ordinary board. Best results are obtained with wood-based panels and plywood. The assembled intarsia is glued mainly with wood glue. It allows you to make corrections, which is not possible with gluing with other adhesives. You can also use PVA glue, but in this case, corrections should be made no later than 1-1.5 hours after clamping in a press or block frames.
The set is glued to the base as follows: the base is smeared with a wide bristle brush, and then the set with warm wood glue; taking water from the glue, the kit will swell and curl. Therefore, it is taken by the transverse sides, placed in the middle of the base and rolled to the brim. Then press and smooth quickly and vigorously with a damp but not wet cloth to prevent curling. Then rub it in with a special hammer until the set is glued over the entire plane, put a cardboard or newspaper on top and clamp it in a press or a bar frame. Intarsia is left in the press for at least 4-6 hours when gluing with wood glue, or 1-1.5 hours when gluing PVA.
Bonding intarsia with a lapping hammer and polishing motion
After taking out the work and freeing it from the paper, check how the intarsia has adhered to the base. Defects such as air bubbles, overlapping joints with plywood are possible. They can be detected by ear by tapping the surface with your finger (a dull sound indicates the presence of bubbles and non-sticky areas).
Defects can be corrected: drive with a hot iron in those places that have flaws; the glue heats up, and rub these places with a grinding hammer until the plywood sticks. It so happens that you need to add a little glue under the plywood. To do this, make a slot, heat the place with an iron and lift the plywood with the tip of a knife. A strip of strong paper is inserted into the slot, smeared with glue on one side; rub in different directions in order to lubricate the inner surface as much as possible; if necessary, this procedure is repeated several times.
The overlap of one plywood with another is corrected as follows: cut off an extra strip of plywood with the tip of a knife, heat this place with an iron, raise the butt joints with the tip of a knife and cut a piece. To prevent the heated glue from sticking to the iron, the places that need to be heated are covered with a sheet of paper. The surface of the product cleaned from paper is leveled and sanded with cycles, glass and sandpaper with medium and fine grain. It is better to level the surface with a handle or a plank wrapped with sandpaper.
Intarsia varnishing
For varnishing, mainly transparent and nitrocellulose varnishes are used, which dry quickly (2-2.5 hours).
Before varnishing the work, you need to take a piece of cloth and clean it of dust. The varnish is applied to the intarsia surface with a swab, brush or spray bottle. After drying (4-6 hours), the swollen and raised villi are removed with fine sandpaper, wiping it over the entire surface of the product. After cleaning the villi with sandpaper, wipe the surface again with a soft cloth and apply a new layer of varnish. This procedure is repeated 3-4 times, applying each new layer only after the previous one has completely dried (4-6 hours). When applying a new layer of varnish, do not cover the same places twice, so as not to remove the layer previously applied.
Individual intarsia jobs benefit significantly on a normal matt surface without varnish and without polishing. To reveal the beauty of wood texture, use a solution of beeswax in turpentine. Products coated with such a solution have a pleasant surface with a bright identification of the texture of natural material (2-3 g of finely chopped wax are added to 100 g of heated turpentine and dissolved). The turpentine evaporates and the wax remains in the wood. Rubbing the surface of the product with a cloth, we get a uniform juicy matte surface.
Intarsia work polishing
Individual intarsia work will look better if finished with polishing. Polished wood brings out its texture more clearly. It is best to use alcohol polish. Compared to nitrocellulose varnishes, varnish is afraid of moisture, therefore, it can only be used to polish dried products and, after polishing, can be stored in a dry room.
The polishing process is much more complicated than varnishing. It consists in applying several thin layers of polish to the surface of the product plane using a tampon or spray gun, and at the same time achieving a smooth mirror surface.
The tampon is made from woolen or cotton fabric. It is wrapped in a clean cloth and impregnated with varnish. After the first layer has dried (4-6 hours), the surface is sanded with fine-grained sandpaper, cleaning off the swollen and raised wood fibers. The second and subsequent times, 2-3 drops of linseed, hemp, olive or ordinary sunflower oil are dripped onto the moistened tampon in order for the tampon to glide better over the surface. A thin, quickly disappearing smear of polish immediately forms on the surface of the product. If the smear does not dry for a long time and small bubbles appear, this indicates that there is more polish in the tampon than necessary. Then squeeze out a few drops of polish, drop two or three drops of oil and start polishing again. If there is no smear at all, there is not enough polish.
It is better to polish by holding the work in a vice in a horizontal position. First, the product is primed with 16% varnish. When priming, wood fibers rise on the surface, which, after drying, must be cleaned off with a sanding cloth. The first polishing is carried out with 8% polish after the primer has dried and the fibers are cleaned, and the second - with 5% polish.
It should be noted that between the individual stages of polishing it is necessary to take a break for several days, the first time is polished one day after the priming, the second - three days after the first, and the third time - 10-20 days after the second.
Finish the work on polishing as follows: with a swab moistened with alcohol, vigorously rub the surface of the product in a circular motion, which becomes mirror-smooth and clean.