GOI paste ( from GOI - State Optical Institute ) - grinding and polishing pastes based on chromium (III) oxide, used for grinding and polishing steel alloys, including thermally hardened, non-ferrous metals, hard plastics and polymers, glass (including optical glass), ceramic materials and products from them.
GOI paste can be used for polishing products from a variety of materials. To date, several of its varieties. For a particular material, choose a specific type of paste. The polishing procedure itself must be carried out correctly. We'll talk about how to use GOI paste.
GOI pastes were developed in 1931-1933. a group of Soviet scientists, employees of the State Optical Institute - I. V. Grebenshchikov, T. N. Krylova, V. P. Lavrov, S. V. Nesmelov.
This polishing tool was developed in our country and for a very long time - in the 30s of the XX century. It was invented by specialists from the State Optical Institute. Hence the name of the paste (in the first letters) - GOI. For nearly a hundred years, this tool has been used for polishing steel, other metals, ceramics, plastics, stone, and even glass. How to use GOI paste, our grandfathers also knew. It was originally made of chromium oxide and auxiliary substances and was green in color. Today, such a tool can also be found in stores and on the market. However, the production of green pasta is currently prohibited and discontinued. The fact is that chromium oxide is a toxic carcinogen. Modern pastes GOI are white or red and are made of aluminum oxide. Using the second type of polishing is faster. Using the same white paste, you can get a better and smoother surface.
GOI paste represents light green or dark green bars , consisting of chrome oxide abrasive powder, organic (fatty) binders and auxiliary substances (activating and intensifying additives). GOI pastes are produced both in the form of bars and in the form of soft (felt) polishing wheels already impregnated with a paste. They are a mixture of chromium oxide (gives a green color, the hue of which depends on the percentage - 65-80%), as well as solvents and chemical reagents - kerosene, stearin, silica gel and others. There are 3 main varieties of GOI pasta: coarse, medium (in images) and thin (No. 1 and No. 2). Coarse has a light green color, is most effective in terms of the volume of material removed, gives a matte surface. Medium has a green color, gives a clean surface. Thin pastes are respectively dark green and black with a greenish tint of color, are used for fine lapping (finishing), give a mirror shine.
Varieties of GOI pastes and their application
According to TU 6-18-36-85, four numbers of GOI paste are distinguished depending on the size of abrasive particles:
- No. 1 (black paste with a green sheen; abrasive ability 0.3-0.1 µm) for fine polishing, gives the treated surface a specular gloss. Composition: 65-70 parts of trivalent chromium oxide, 1.8 - silica gel, 10 - stearin, 10 - split fat, 2 - kerosene, 0.2 - two-carbonic (drinking) soda;
- No. 2 (dark green paste; abrasive ability of 7-1 microns) for fine polishing, gives a glossy finish to the treated surface. Composition: 65-74 parts of trivalent chromium oxide, 1 - silica gel, 10 - stearin, 10 - split fat, 2 - kerosene, 2 - oleic acid, 0.2 - bicarbonate soda;
- No. 3 (green paste; abrasive ability of 17-8 microns) for medium grinding, gives a clean surface without strokes and is used to achieve an even gloss of the polished surface. Ingredients: 70-80 parts of trivalent chromium oxide, 2 - silica gel, 10 - stearin, 10 - split fat, 2 - kerosene;
- No. 4 (light green paste; abrasive ability of 40-18 microns) for rough grinding, gives a matte surface and is used to remove the smallest scratches left on the surface after grinding with abrasives. Composition: 75-85 parts of trivalent chromium oxide, 2 - silica gel, 10 - stearin, 5 - split fat, 2 - kerosene.
Produced a green variety in solid bars, and in the form of a more liquid pasty mass (in the boxes). The popularity of both types is due not only to high quality polishing, but also more than affordable price.
The abrasive ability of the GOI paste is determined by the thickness of the metal removed from the steel plate 9 × 35 mm when it passes the 40 m path along the cast iron plate 400 × 400 mm.
|No||Type of pasta||Pasta color||Abrasive ability, micron|
What you need to do before polishing
So, let's start to understand how to use GOI paste. The small particles in it, when rubbing the surface, remove a thin layer together with scratches and microcracks. Polishing is usually done with a soft cloth dipped in gasoline (you can use a lighter). A small layer of paste is applied to it and a little rub off of it on an unnecessary piece of metal. This is necessary in order to break all too large pieces in the paste. If they remain, the surface can not be polished, but rather scratched. Cloth should be really soft. You can take, for example, flannel. Sometimes the paste is applied to the polishing disc. Directly on the surface of the processed product can not be smeared. The product is lightly pre-coated with industrial liquid oil ("spindle").
GOI pasta: how to use
So, a rag with pasta cooked. Now you can proceed directly to the polishing. To do this, you just need to rub the surface. Do not press on the product too hard. Otherwise, even more scratches may appear on it. For the same reason, too sharp hand movements should be avoided. Continue polishing until a completely smooth surface is obtained. From time to time, as needed, a little “spindle” should be applied to the product.
How to polish with GOI paste items with a lot of deep defects? Usually in such cases, the surface is pretreated with option # 4. Then go to number 3. Finish treatment number 2, and the final gloss induce the means number 1.
After the operation is completed, rinse the product in kerosene. The latter can be purchased at the pharmacy. If this cannot be done, it is allowed to wash the polished object in running water. In some cases, the surface of the product after processing, rinsing and drying is additionally covered with zaponlakom. This allows to significantly slow down the oxidation process. The knives are polished with a bar with leather stretched over it.
How to use GOI paste on glass and plastic
Very often, this tool is used to bring in the "divine form" of cell phones. In this case, you will need to polish, first, the case itself, and secondly, the display glass. Since plastic material is rather soft, for its processing it is necessary to use sparing paste from jars No. 2. Otherwise, the case can be scratched even more. The answer to the question of how to use GOI paste for plastics is simple: just like when processing any other materials.
The glass is pre-polished with special rubber circles. Next, use the actual GOI paste. The procedure in this case is the same, that is, using a rag. Oil and gasoline when processing phones do not apply.
How to use GOI paste for cleaning silverware
As already mentioned, this tool, both green and red or white, can be applied to the processing of absolutely any metals. It also concerns silver. You can safely use GOI paste to brighten your spoons, cups and forks.
How to use GOI paste for silver cleaning? Before proceeding to polishing, the product should first be thoroughly cleaned with a toothbrush with tooth powder applied on it.
Then pour some ammonia into a glass of water, shake soap and pour a little bit of powder. All this must be thoroughly mixed to complete dissolution. Next, the liquid is poured into some enamel saucepan. After that, silver cutlery falls into it. Then put the saucepan on the fire and bring the liquid to a boil. After that, the silver should be removed and rinsed in cold water. Next, you can proceed to its processing paste GOI according to the method described above.
What can not be polished
Next, let's see in which cases the GOI paste cannot be applied. How to use it, you now know. However, in no case can not use this tool for processing gold-plated things. Otherwise, the top valuable layer will be very quickly erased to the bottom metal. Steel (except knives) and nickel are usually processed not manually, but using a special machine. Polishing of metal watches is also made with a cloth. However, they must first be disassembled and the mechanism pulled out. Do not start polishing too scratched surfaces with option number 2 or 1. In this case, the defects will become even more noticeable. The sapphire glass on the watch cannot be polished with GOI paste. She simply does not take them.
Where the tool is used
With how to polish paste GOI, we figured out. Now let's see exactly where this tool is used. GOI paste is used not only at home for polishing, silver, watches, dangerous blades and razors, etc., but also in production. In the latter case, it is used most often in electroplating shops for processing products from non-ferrous and ferrous metals. Polishing is performed using special polishing machines with felt circles.
Today, on sale can be found and imported versions of these pastes. A very popular option is the French Dialux. The latter is distinguished by a firmer consistency and is worse applied to the skin of the bar when sharpening knives than the GOI paste. Dialux is considered more convenient to use. It is possible to polish metal surfaces with it much faster and with better quality. However, such pastes are more expensive. There are more types of Dialux than GOI types. Available this tool in the bars, packaged in paper of different colors. According to them you can navigate in terms of using Dialux for a particular metal.
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