How is the walnut paint surface applied in European classical furniture?

Modern European classical furniture, as a type of antique furniture, is highly sought after and loved by people for its solemn, elegant, and practical characteristics. Elegant without affectation, lyrical without frivolity, full of humanistic charm, showcasing European classical sentiments to the fullest. The surface coating of such furniture not only has a rich color and rich layers, but also is an organic layer of value and history.

Especially dark colored finishes, such as walnut and glass colors, are a more pure expression of the luxury and solemnity revealed by European classics. Therefore, the painting process is crucial for modern European classical furniture. This article only takes the walnut paint surface painting process as an example to briefly describe such production processes, and then provides a reference discussion on the surface decoration of European classical furniture.

1 What is the Painting Technology of European Classical Furniture

The painting process of modern European classical furniture is quite complex in terms of coating selection and process scheduling. In addition, the strict requirements for the working environment and construction techniques make this process require strict technical management. From the perspective of paint and coating, currently European classical furniture mostly uses NC (nitrocellulose paint) coating to express the surface with dark color, multi-level and antique effect. This type of coating not only dries quickly, is hard and wear-resistant, but also has good repainting performance, making it easy to repair colors. Its good transparency better highlights the beauty of the material itself. The walnut color paint film process mainly uses transparent nitrocellulose wood paint, which includes nitrocellulose transparent putty, transparent primer, transparent topcoat, etc. Its main functions include sealing the color of the lower layer, color layering, and surface brightening.

From the perspective of surface coloring, European classical furniture with walnut paint surfaces requires multiple coloring treatments to have a certain antique effect. Different colorants have strict formulas, coloring methods, and coloring sequences. Commonly used colorants include material finishing agents, base finishing agents, Grace, surface finishing agents, etc. Among the many colorants used in walnut paint films, walnut pigments and dyes are added.

The process of walnut paint finish on classical furniture can be generally summarized as patching work, coloring work, primer spraying work, sanding and painting polishing work, and topcoat spraying work.

2 Introduction to the Painting Technology of European Classical Furniture

Ash filling, also known as putty filling, is mainly carried out in the bottom and primer sections. The types of fillers used and the purpose of the ash filling operations in the two sections are different.

2-1 Ash filling operation in the bottom section

The so-called bottoming refers to the pre-treatment of the substrate before coating, which involves using fillers to fill natural and artificial defects such as holes, nail holes, scratches, and assembly gaps on the surface of the substrate, in order to obtain a relatively flat surface.

In practical work, workers often use colorless refined atomic putty (unsaturated polyester putty), brown red putty, and brown yellow putty, and then mix these three types of putty in different proportions based on the final color of the product, and finally add curing agent. Therefore, the blending of putty color and the control of dry curing time have high requirements for construction experience.

During the ash filling operation, different scrapers should be used according to the size of the product defect. When adding ash, it is necessary to scrape vigorously along the direction of the wood grain to achieve uniformity and compaction. It is best to make the nail holes and missing parts convex (they will naturally settle after drying). For pinholes and bubble holes on the substrate, the patching method is used, while for locally formed pores, the scraping method is used. If the defect is large (the diameter of the cavity is greater than 2mm, and the width of the crack is greater than 1mm), it can be filled with glue mixed with wood ash.

2-2 Ash filling operation in the primer section

After the first primer operation of the product, it is necessary to continue to repair the surface defects with secondary leveling and color difference adjustment, which is the main purpose of the operation. At this stage, a brownish red oily putty is used, that is, an appropriate amount of transparent putty is placed on the putty board, and then a curing agent is added in a 5:1 ratio, followed by an appropriate amount of talcum powder. The corresponding color essence is added according to the walnut color product color board (refer to C.IPigment Red 101 (77491)).

In the secondary ash filling work, the first step is to check if there are any unfilled or omitted areas in the first water-based ash, and carry out the secondary ash filling. For obvious color differences on the surface, color correction should be carried out.

It is particularly important to consider whether the performance of the putty ash matches that of the painted paint when color matching and patching. For example, products sprayed with NC paint (nitro paint) cannot be supplemented with PU (polyurethane resin) based ash. And the ash filling must be slightly raised so that the subsequent process can be polished smooth, but the area of ash filling should not be too large to avoid affecting the overall effect of the product.

03 Walnut color paint surface coloring process

The coloring process is an important part of European classical furniture, which not only determines the surface color and final coating effect of the finished product, but also affects the physical and chemical properties of the overall paint film. Walnut colored antique paint surface is formed by various coloring substances according to certain processing methods.

3-1 Material color correction

European classical furniture has a large volume, and most of them use solid wood splicing materials. There is often color difference in the visible surface of the materials. If the color is not pre adjusted in advance, the subsequent coloring will be affected. Therefore, before formal coloring of wood, material color correction agents should be used to reduce color differences.

The walnut paint surface requires the material to have a brownish yellow background color, which means that the light colored part of the material needs to be dyed into a dark color. The reagent used in actual production is called "red water", which is a brown paint made by mixing pigments and dyes.

It should be pointed out that if the color difference of the material is too large, bleaching treatment should be carried out before the material color trimming. The bleaching water is mixed by hydrogen peroxide (30% - 35% by mass) and ammonia (23% - 25% by mass) at a volume ratio of 1:1, and can be mixed within 24-36 hours.

3-2 Base color coloring

As the first overall color application on the surface of furniture, the base color sets the tone of the product color. The walnut paint finishing process often uses two coloring substances, commonly known as "red water" and "yellow water". The "yellow water" here is a brownish yellow paint made by mixing pigments and dyes, often sprayed after the red water is sprayed, mainly to highlight the wood texture.

In actual homework, it is necessary to first try coating a product and compare it with the walnut color palette. If no differences are found, mass production can be carried out. Often, when producing 5-6 products, it is necessary to match the color once to ensure that the color does not deviate. When spraying, for dining chair, frame products or components, the spraying sequence should be from inside to outside; Chairs and other items should be sprayed from top to bottom; Plate components, on the other hand, are sprayed first on the reverse side, then on the front side, and then on the edges. It should be noted that when repairing the base color, it must be sprayed wet, but water droplets cannot be formed, and the color cannot be sprayed or curled.

3-3 brush off

Color wiping operation is an important process step in obtaining a rich and layered color tone on the surface of European classical furniture, and is the most "brilliant" process for walnut paint surfaces. The pigment used is Grace, also known as antique paint, which is an oily pigment colorant that uses its own translucency to reduce the surface brightness of the product, forming a layered contrast effect between light and dark.

In production, workers often use cotton cloth as a wiping tool, and the cotton cloth should not be dipped too much in oil to prevent waste and oil flow. During the wiping process, wipe clockwise first and then in the direction of the wood grain. The paint applied to the surface of the product should be wiped clean in a short period of time. If there are flow marks on the paint, it should be immediately removed. But for the trunking and corner parts, it is necessary to first brush them in place and then wipe them with a cotton cloth.

3-4 Facial color and edge trimming

After the previous series of color treatments, furniture products need to undergo the final color correction, which is to adjust the color according to the walnut color palette. Firstly, to create the corresponding effect according to the color palette, and secondly, to further deepen the color contrast. The parts for color correction are mainly concentrated on the surface and edges. The former is called "surface color correction" in production, while the latter is called "edge correction". The color additive required for color correction is an alcohol soluble reagent with color correction essence added. The ratio of its main agent, curing agent, and diluent is usually 1:0.5:0.7-1.

In the operation, the edge and the surface can be repaired by the spray gun and brush, and the steel velvet can also be locally rubbed after coating the reagent, so as to obtain the required effect of doing old.

If the product contains different components, it is necessary to adjust the color by increasing or decreasing the number of sprays to ensure consistency in color. At the same time, for each finished product, two steps should be taken back to observe whether the overall color is uniform and consistent, and corresponding treatment should be carried out.

4 Spray painting process for European classical furniture

The types of paint are diverse and complex, but they often have strong adhesion and sealing properties, and are the main film-forming substances on the surface. The formation of walnut colored paint film on European classical furniture needs to be combined with multiple uses of paint. It is commonly used after each coloring process to help seal the bottom layer color and adhere to the upper layer color, while determining the final visual and physical properties of the paint film, such as glossiness and wear resistance. Therefore, the painting and spraying process on the surface of furniture is crucial.

The walnut paint coating process introduced in this paper mainly uses nitrocellulose series paints, including nitrocellulose primer and nitrocellulose top paint. This paint has the characteristics of fast drying, hard wear resistance, good recoating and good transparency. In the bottom, also need to use PU sealing primer, sealing strong, thick coating is its main advantages.

4-1 Spray primer process

The primers used for walnut colored paint surfaces include PU (polyurethane resin paint) sealing primer and NC (nitrocellulose paint) environmentally friendly transparent primer. Generally speaking, the first primer uses PU sealing primer with good sealing performance, and the subsequent 3-4 primer processes mostly use NC environmentally friendly transparent primer. Before spraying, factors such as weather and temperature changes should be considered, and auxiliary agents such as slow drying agents and anti white water should be added reasonably according to regulations.

For chair frame products, the distance between the nozzle and the spraying surface during spraying is 15-20cm, and the oil mist is adjusted slightly finer, with a spraying width of 8-10cm. The air pressure of the spray gun should be adjusted appropriately based on the amount of oil, and should not be too large or too small, as it may lead to waste of paint or insufficient spraying. When spraying, the hands should be stable, and the gun speed should be slightly slow and uniform. First, spray the inner side of the lower part of the chair frame and the outer side of the lower part of the chair frame, and then spray the back side of the upper part of the chair frame and the front side of the upper part of the chair frame.

For flat panel components, the distance between the nozzle and the spraying surface during spraying is 15-25cm, and the oil mist is slightly wider, with a spraying width of 15-25cm. First spray the edge of the flat surface, then spray the front side, and then move the gun in a "+" shape. After the front side dries, spray the back side.

Sprayed products must reach the specified drying time, and PU primer products must be dried for 8-12 hours; NC primer products must be dried for at least 2-3 hours. It should be noted that when the temperature is above 40 degrees Celsius or below 0 degrees Celsius, and the humidity is below 70%, the operation should be stopped to prevent the occurrence of paint whitening.

4-2 Topcoat spraying operation

The scratch resistance, hardness, luster, feel, transparency, aging resistance, and yellowing resistance are mainly reflected in the topcoat, so the spraying process of the topcoat directly affects the quality of the entire surface coating.

Before spraying the topcoat, a series of dust and dust removal measures should be taken first, such as turning on the water curtain machine, air intake and ventilation equipment, and maintaining air convection in the spraying room. In addition, it is important to keep the ground clean, damp, and dust-free. Close the doors of the dry area tightly to prevent dust from entering. For products to be processed, dust removal must be carried out using an air gun or cloth before painting.

The operation sequence when spraying the topcoat is basically the same as that of spraying the primer, so it will not be repeated. The color of the sprayed product must be basically consistent with the walnut color board, and the paint film thickness must be moderate. As for the drying time of the topcoat, NC topcoat should be at least 12 hours or more, and the drying time of bright products should be at least 45 hours. The temperature and humidity in the drying room should be well controlled. Generally speaking, the humidity inside the room should be maintained below 70%.

5 Sand ash and polishing process

As the saying goes, "A great paint job is all about sanding." This highlights the importance of sanding in the finishing process. Especially for paint polishing, it is a necessary process for multiple spraying. On the one hand, appropriate polishing can make the colorant better adhere to the surface of the paint film. On the other hand, the polished paint film can better combine with the subsequent paint film, thereby enhancing the physical and chemical properties of the paint film. The walnut paint surface mainly uses nitrocellulose paint, and combined with its old craftsmanship, the selection of sandpaper model and sanding method is particularly important.

In practical operations, if there are process lines in the product, the lines are usually ground first and then the flat surface is ground. Grind the concave process slot by cutting 240 # sandpaper into strips, folding them manually for polishing, and then using 320 # sandpaper to remove sand marks; The convex shape is first manually polished with 320 # sandpaper, and then the sand marks are removed with 400 # sandpaper. It should be noted that during manual polishing, the strength should be controlled to avoid sand leakage of the product, and dust should be blown away while polishing to see the degree of polishing.

For the polishing of the flat surface, it is necessary to first use 240 # sandpaper for machine grinding, then use 320 # sandpaper for machine grinding, and then use 320 # sandpaper for manual grinding to remove all the ring marks of the machine along the fiber direction. In addition, if the walnut paint surface needs to be polished, it needs to be sanded with a 320 # sandpaper machine first, and then manually polished with a 400 # sandpaper.

The process of walnut colored paint on European classical furniture is complex and diverse, based on the pre-treatment of materials before painting, the key is the combination of multiple coloring and painting, and the focus is on appropriate and reasonable polishing operations. Only when the various processes are fully coordinated and combined can the practicality and aesthetics of the paint film be guaranteed. The painting method described in this article is only one of the surface decoration techniques of European classical furniture, and thus the extraordinary charm of this type of furniture painting technology can still be seen.