Traditional tools for stretching canvas are small hammers and spikes. When the canvas is cut, it should be three to four centimeters longer than the inner frame, not smaller. Start from the middle of the four sides of the inner frame (note that the canvas should be nailed to one side of the inclined inner frame). Tighten the canvas, first nail three nails on each side, as shown in figure 19. Then nail from the middle to the four corners in turn, and the nail spacing is about 3 ~ 4 cm. Don't nail all the nails to the battens, so as to adjust or disassemble the canvas. The appearance of special tools such as gun stapler, nail gun and wide-mouth pliers makes the method of stretching canvas labor-saving and interesting. As shown in Figure 20, first nail three nails in the middle of the long side of the wooden frame with a nail gun, then turn the wooden frame over and tighten the canvas with wide-mouth pliers, and nail three more nails on the opposite side. Nail the two short sides in the same way. With the help of pliers, tighten the canvas from the middle to the four corners in turn. When wrapping the corner, fold the canvas and tighten it with pliers, and then nail it with a nail gun. Canvas with extra edges can be fixed behind the photo frame. If there is no gun stapler, you can use an ordinary stapler instead. When using ordinary stapler, pay attention to remove the base, and when stretching the canvas with ordinary pliers, don't use too much force to avoid damaging the canvas.

It is convenient and practical to stretch the canvas with traditional methods and replace the studs with pushpins.

For a frame that does not need an outer frame, the canvas should be about five centimeters larger than the inner frame when stretched. Nails should be nailed on the back of the inner frame, and the corners should be hidden, as shown in Figure 2 1.

2. How to prevent the frame from deforming when the canvas is stretched?

After the canvas is stretched, there are three reasons why the picture is uneven and the picture frame is distorted: First, the quality of the inner frame itself is not good, and the seams at the four corners are not standardized. Second, the canvas is skewed. If the canvas is torn by hand, it is easy to deform, resulting in that the four sides of the canvas are not parallel to the four sides of the inner frame. Third, the stress is uneven when stretching the canvas.

Solution: If it is the problem of the inner frame, replace it with a good quality right-angle triangle or nail it at the four corners. If it is a canvas problem, check whether the four corners of the canvas are at right angles before stretching. Fold the canvas in half in the middle to see if the four corners are aligned. If they are not aligned, it means that the canvas is tilted. It is necessary to restore the square of the canvas by pulling, and at the same time change the method of stretching the canvas from the middle. First, wrap and fix the four corners of the canvas, and then flatten and fix them one by one with wide-mouth pliers. The key is that the distance between the painted canvas edge and the outer edge of the inner frame should be equal, so that the frame is not easy to deform. Another method is to fix one side of the canvas (first fix the two corners on this side), then fix the other two corners and the corresponding cloth edges, and then fix the cloth edges on both sides. At the same time, be careful not to use force when pulling canvas with wide-mouth pliers, and use force evenly. As long as the latitude and longitude lines of the canvas are parallel to the outside of the wooden frame, there will be no distortion of the frame.

3. What should I do if the canvas is easy to loosen after the bottom is done?

Due to the quality problem of canvas, it is easy to change the tightness after wetting. As a canvas with large shrinkage after wet water, wet stretching method is generally not used. If you use a finished oil canvas with a base, you need to spray some water evenly on the canvas before stretching, and then stretch it on the inner frame after it is soft, so as not to break the base.

For a picture frame with a wooden wedge, the wooden wedge should be driven into the inner corner of the inner frame after the canvas is stretched. After the foundation is laid, tapping the wedge gently will make the canvas taut. If it is a big picture frame with a dead angle, it is a headache for the painter to loosen the canvas after the bottom is finished. Pure flax woven with thick thread generally does not appear slack, and famous painters also use high-quality flax. If ordinary linen or cotton-linen blended fabric is used, fix the canvas on the frame with thumbtacks, wet the cloth with water, and then tighten the canvas after the cloth is dry. The purpose of using pushpins is to facilitate disassembly. If the canvas is greatly relaxed after the first wetting, it can be repeated, and finally the canvas is fixed with a gun stapler. Be careful not to lift all the pins at once, but fix them while lifting them.

The stretching method of large picture frame should first fix the four corners, and then fix the canvas from the outside to the inside. Or after the four corners are fixed, simply fix the four sides, wet them with water, and then carefully fix them after the canvas is dry and loose, so that the canvas will not become loose easily. If the canvas is stretched too tightly for the first time, the wooden frame will sometimes be uneven. Cotton canvas is easy to shrink when wet, and easy to relax when dry. It is best to adopt a simple fixing method first.

On cloudy days, the air is humid and the canvas often looks slack. If you relax a little, it will naturally tighten after the weather is fine and will not affect painting. If it is too loose, it should be tightened, but not too tight, so as not to shrink the canvas and deform the wooden frame after sunny days.

4. Why is linen the first choice for canvas?

/kloc-After the 6th century, canvas became the main supporting material of oil painting. Among many flax and cotton fabrics, pure flax is the most ideal canvas.

The price of pure flax is higher, so there are cheap varieties such as semi-flax, cotton and linen blended. Because cotton and hemp will expand and contract with the change of humidity, blended textiles are not suitable for canvas.

5. How to identify the quality of linen?

(1) Check whether the longitude and latitude lines are even. If the warp and weft are too uniform, it may be cotton fabric.

(2) Tighten the cloth sample and check the knitting density.

(3) High-quality primary color linen is brown, shiny and even in water absorption. Flax with poor hemp quality is treated into soft fiber, which absorbs water unevenly and turns black when wet.

(4) Worsted linen outside, the less plush on the surface, the better.

(5) The vertical and horizontal tightness of semi-hemp is different.

(6) Pull a thread. If the two ends are bent and bifurcated, the thread is cotton thread. The torn flax thread should be smooth at both ends, otherwise it will be impure.

(7) If caustic soda is applied to the canvas, linen will turn brown and cotton will turn pale yellow.

6. Why is it based on canvas?

As canvas, linen and other textiles can only be used after pretreatment. The so-called "processing" means "doing the foundation". The reason is:

(1) Fill the pores between textile textures to create a textured surface that saves pigments and is suitable for painting. Textiles are porous, so it is a waste of time and materials to paint directly on them for more exquisite paintings. Only by painting on the paved canvas can we effectively control the use of oil painting pigments.

(2) The supporting material is isolated from the paint color layer to prevent the oil in the pigment from corroding the fiber, and at the same time, to prevent the water penetrating from the back of the canvas from damaging the color layer. Acidic substances in oil painting pigments will make the canvas dirty, while moisture will oxidize the oil molecules in the color layer and make it aging. Therefore, the treatment of canvas foundation is directly related to the life of the work.

(3) A good canvas foundation can ensure the brightness and vividness of the colored layer. Unqualified foundation or canvas without foundation will make the picture gloomy after coloring.

(4) Brightening the background can improve the brightness of the picture color. (See "How does the background color affect the picture?" )

(5) Once the supporting materials of oil paintings or Tempelina paintings are corroded, the color layer can be transplanted from the old supporting materials to the new supporting materials through "back transformation".

7. What are the materials for oil painting?

(1) glue

Glue used to make canvas substrate includes: animal glue (bone glue, leather glue, etc. ), synthetic rubber such as vegetable resin latex and white latex.

(2) Oil

Oils used to make oily canvas base materials include turpentine, linseed oil, polishing oil and other media.

3) Supporting materials

Auxiliary materials: pure flax, semi-flax, cotton canvas, etc.

Hard supporting materials: wood board, plywood, fiberboard, cardboard, metal plate, etc.

(4) Filling materials

White powder is also called chalk powder, Spanish white, Paris white, clay and so on. , mainly composed of calcium carbonate. The big white powder sold in the market is a mixture of 60% calcium carbonate and 40% magnesium carbonate. When making primer, only glue can be used to combine. If it is combined with oil, it will become greasy. You can use marble powder instead of white powder.

Lead white powder (lead carbonate): In ancient China, it was called official powder and Hu powder. Ancient European painters used it to make basic or white pigments. Because of its toxicity, modern painters have rarely used it.

Gypsum powder (calcium sulfate): based on natural hydrated gypsum or plaster of Paris. It is denser and brighter than chalk, but less flexible. It is best to make gypsum foundation on hard supporting materials such as wooden boards.

Titanium dioxide: Strong hiding power, often mixed with white powder.

Lithopone (zinc sulfide and barium carbonate): The scientific name is Lithopone. Some material experts do not advocate the use of lithopone alone, but can be mixed with large white powder.

(5) Gypsum finished primer

(6) Auxiliary materials

Glycerol and honey: adding a little can increase the elasticity of adhesive.

Alum: Add 10g alum to one kilogram of glue solution to prevent moisture.

Formaldehyde: Spraying both sides of canvas with 4% formaldehyde solution can prevent corrosion, insects and moisture.

8. What are the basic types of classical oil painting?

Classical oil paintings need to be painted on wooden boards or canvases, and the materials used in foundation are bonding materials and filling materials. According to different materials, there are eight ways to make the foundation of classical oil painting.

9. How to use latex as a primer?

Latexes include plant resin latex and synthetic resin latex. Using water as solvent, the dried film is elastic and transparent, and it is a qualified material for making canvas substrate. At present, the white latex sold in shops belongs to synthetic resin latex-vinyl glue. The most suitable white latex for painting materials is polyvinyl acetate emulsion, which has high concentration, bright paint film after drying, high transparency, toughness and no cracking.

The quality of latex is very important to the canvas foundation. When the rubber bottom is dry, press it on the back of canvas by hand. If there is cracking sound, it means that the quality of latex is not good. When buying latex, you should open the box cover to check its concentration. The higher the concentration, the better. Latex mixed with water is not easy to store. If there is dry latex skin on the edge of the box cover, check its transparency and elasticity. Hard and fragile cannot be used.

1 1. What are the characteristics and manufacturing methods of oily foundation?

Oily foundation has the longest history and is the most popular. Mainly used for canvas, but also suitable for wooden boards. Oil base is basically composed of rubber base and oil layer. The traditional primer is animal hide glue (mostly rabbit skin), and the primer is oily paint (linseed oil 15g+ turpentine 15g+ lead white 25g). The production method is as follows: after the leather glue is heated and melted by adding water, it is coated on canvas while the glue solution is warm, and then coated with white oily primer after drying. The oil in the primer should be as little as possible to ensure that the subsequent colored layer is firm. Canvas can be used by priming, but if a smoother surface is needed, the canvas should be smooth, so priming should be applied two or three times. It takes several months to make a canvas with an oily foundation, and the longer the better. The ideal time is half a year.

12. What are the characteristics and production methods of semi-oily foundation?

Semi-oily primer is also called semi-absorbent primer, which is generally painted with latex paint, so it is also called emulsion primer or Tan Perez primer. There are many ways to use animal glue, latex, casein glue or egg yolk as emulsifier.

(3) casein gum base:

① Preparation of casein glue solution: 50g casein+125ml warm water+15g ammonium carbonate. Note: firstly, stir casein with warm water, and at the same time dissolve ammonium carbonate with very little water, and pour the dissolved ammonium carbonate into the stirred casein solution. After casein is completely dissolved, add 125ml warm water and stir it into paste. Then add 3g sodium chloride (preservative), dissolve it in water, and then pour it into the glue solution and stir it evenly.

② Take 1 part synthetic casein glue solution+1 ~ 3 parts water to brush the first glue base.

(3) After the first layer is dried, brush the coating agent.

Preparation of coating agent: 1 part of white powder+1 part of titanium dioxide or zinc powder+1 part of water+1 part of casein glue, then shake a few drops of ammonia water into emulsion, and then mix them together for later use.

(4) Egg base: Beat the yolk or whole egg into the glue solution, then slowly drop some linseed oil, and form an oil-in-water viscous emulsion by stirring or shaking. Mix white powder and water into slurry in advance, then mix with oily emulsion (you can add some honey), and coat two or three layers on the painting base coated with thin glue. In the past, refined bone glue or glue was used as glue solution. Latex, cellulose glue and 107 glue can be used today.

At present, most of the oil paintings sold in domestic art stores are semi-oil-absorbing canvases. The characteristics of semi-oil-absorbing canvas are between rubber-based and oily-based.

13. How does the production of color background affect the picture effect?

The basis for making colored paintings probably existed in the Gothic era. From16th century to19th century in Courbet, it was very popular to make red canvas with red basalt soil. Some are coated with a color isolation layer of oil and resin on the colloidal substrate, and some are coated with a red clay pigment with strong absorption when the last layer is coated on the oily substrate. Doing so can not only weaken the greasy feeling of oily foundation, but also help the painter to grasp the overall tone of the picture.

Rubens once mixed hard charcoal, white pigment and adhesive (possibly glue) and quickly coated it on the white gypsum foundation with a sponge, resulting in a textured silver-gray layer, which made the subsequent color layer look relaxed and full of vitality.

Here are two ways to make colored foundation:

(1) On the chalk base, the white base is coated with propylene pigment, turpentine and a small amount of colored oil. The acrylic pigments used are prepared according to the needs of painters, such as white, brown, ochre and earth tone.

(2) On the oily or semi-oily foundation, adding a little iron red powder (iron oxide) and Bo Tu with color oil quick-drying agent or daubing it at will to keep the brush marks, which will produce unexpected effects.

(3) On the basis of sketch, adjust the oil painting pigment with turpentine and thinly coat it with a color layer opposite to the final color. For example, the sky is blue, but first Bo Tu is covered with red earth.

The color substrate must be made on a white substrate, and Bo Tu cover dyeing method is adopted. The purpose is to ensure the transparency of the color of the picture. No matter how thick the subsequent coloring layer is, the background color will have an impact on the picture.

(1) White background can show the richness of color to the greatest extent. On a white background, the color is clear and definite. All colors are difficult to combine properly and organically on a white background, and can only be adjusted by the gray produced by mutual harmony, so painting on a white background needs rich gray. In the use of color, the contrast between cold and warm should be appropriate, and excessive coloring should be avoided. White background is suitable for transparent and translucent paintings. By using this technology, various "visual grays" can be produced, which were once adopted by ancient masters such as Rembrandt and Van Dyke. This gray is more attractive than the adjusted gray.

(2) The gray background has an earthy smell, which is often adopted by many painters and plays an irreplaceable role in human skin color. A gray background can make various colors have a harmonious and unified effect. The silver-gray background is between white and gray, which has the characteristics of * * * two background colors. Gray-green background can weaken warm color, earth red and ochre background can weaken blue-green tone and make colors tend to be harmonious. The contrast of cold and warm formed by color and background color can obtain extremely subtle effect. At present, many painters use the primary colors of linen-light brown and brown as the background color, which reduces the trouble of making the background color and is convenient and practical, but it is only suitable for fine linen and medium density linen. Coarse flax needs fillers (lithopone, white powder, etc. ) to fill the fabric holes.

(3) Painting on a dark background will dim the picture. All light colors will darken, so take this change into account when using a dark background color. Dark backgrounds are mostly warm colors, such as brown and iron red. Painters generally don't use black background, but ivory black plus white background is often used.

14. What are the characteristics and manufacturing methods of gypsum foundation?

Pure gypsum foundation-Rubber gypsum foundation was produced in the Middle Ages and is the best foundation for hard supporting materials (plates, etc.). ). Gypsum has strong adhesion and is compatible with most color matching media. Besides propylene, it is especially suitable for oil painting pigments, because it is a completely oil-free base material.

At the end of the Middle Ages, that is, at the beginning of oil painting, most easel paintings were painted on wooden boards, and gypsum was used as the foundation. Gypsum base contains no oil, is not easy to turn yellow, and can keep pure white. Therefore, the classical transparent oil paintings from14th century to15th century still shine like gems.

The traditional manufacturing method of gypsum foundation is as follows:

(1) basic materials. Animal hide glue or water glue 70-100g, water1l. Apply it two or three times. You must wait until the first layer of glue is completely dry before applying the following layers.

(2) Primer. Glue solution, zinc white and gypsum each 1 serving.

15. How to use oil painting paper and board?

In addition to canvas, oil painters also use oil painting paper, boards and other materials to paint.

Oil painting paper is made by sticking a layer of linen on the surface of thick cardboard, and the thickness is generally 4 ~ 6 mm Oil painting paper sold in the market should be brushed with diluted latex before use to avoid oil absorption. Oil painting paper is mostly used for going out to sketch, making color drafts, emergency sketch classes, etc. Holbein Jr., Rembrandt, Delacroix and other European painters all left paper-based oil paintings, but the oil paintings used at that time were made of rags, unlike today's paper, which is mostly made of plant pulp, and some paper-based oil paintings are stuck on boards or cloth.

Wood board was the main painting material chosen by ancient European masters before oil painting on canvas appeared. Choose pine, Chinese fir, cypress, basswood, poplar, etc. Nowadays, painters seldom paint on boards. Some painters use plywood (plywood or plywood), nail the plywood (plywood) to the wooden frame, mix latex with a small amount of water and lithopone or white powder into a semi-fluid, scrape the latex onto the board with a scraper, dry it, gently polish it with sandpaper, and then brush a layer of latex water. Plywood can also be used as rubber soles. In order to increase the adhesion of plywood to color, it is a better way to stick a layer of thin linen (cotton cloth is also acceptable) on the board before making the foundation. First, soak the cloth in latex water, and at the same time, Bo Tu a layer of glue on the board surface. Then, lay the soaked cloth flat on the board surface and brush it flat with a brush. Plywood must be fixed on the wooden frame first, otherwise it will be deformed. If the frame is small, the plywood area is not large, and the wooden frame is not nailed, glue can be brushed at the same time.

It is inconvenient to carry a picture frame when going out to sketch, and it is not easy to save it when using oil painting paper. It is very practical to stick linen to plywood for painting. Since you don't need a big picture when you go out to sketch, plywood doesn't need to be fixed with wooden strips. If the frame is larger, you can use five folding plates.

16. How to classify oil painting pigments?

17. What's the difference between lead white, zinc white and titanium white?

The chemical composition of lead white is lead carbonate, which makes the oil painting have better color coverage. Lead white powder is often used as a basic material. Lead white is the best white pigment in oil painting color at present. Pure lead white is very stable. If the ingredients are impure, they will turn yellow after a long time. The color of lead-white oil painting dries quickly, and the color layer is firm after drying. It is the best white color in traditional European oil painting and has been used by many oil painting masters. However, lead white is very toxic, and even inhalation of dust containing lead white will have serious consequences, so grinding lead white will bring danger to people. Most of the white oil painting pigments produced now are zinc white, titanium white or zinc titanium white.

The chemical composition of zinc white is zinc oxide, and its scientific name is zinc oxide powder. Zinc white powder is slightly lighter and whiter than lead white powder, and keeps yellow and stable for a long time. After drying, the color layer is thicker, but it is not as thick as lead white powder because of eating more oil. Dry slowly and brittle easily. European painters began to use zinc white pigment from 1840. Zinc white will turn into lemon yellow when heated (directly exposed to the sun) and turn back to white after cooling. Zinc white is nontoxic, colder than lead white, and tends to be blue.

The chemical composition of titanium dioxide is titanium oxide, which is an inert pigment. Not affected by climatic conditions, strong hiding power. It is a modern pigment. Pure titanium dioxide dries quickly and turns yellow easily after drying, so it is often mixed with zinc white. Zinc titanium dioxide not only reduces the brittleness of zinc oxide, but also improves the shortcomings of titanium dioxide used alone. Titanium dioxide has the same non-toxic advantages as zinc white. Zinc titanium dioxide is a white pigment widely used in China at present.

22. How to develop oil painting pigments?

Pigment powder (available in some chemical shops and art shops in China) can also be made by ourselves, and can be used to trial-produce soil or minerals with beautiful colors that can be seen in life.