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, glasses (including optical glass), ceramic materials and products from them.
GOI paste can be used for polishing products from a wide variety of materials. To date, several of its varieties are produced. For a particular material, you should choose a specific type of paste. The polishing procedure itself must be done correctly. We will 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 agent was developed in our country and a very long time ago - in the 30s of the XX century. Invented by specialists from the State Optical Institute. Hence the name of the paste (in the first letters) - GOI. For almost a hundred years, this tool has been used to polish steel, other metals, ceramics, plastics, stone and even glass. How to use GOI paste, our grandfathers also knew. Initially, it was made from chromium oxide and auxiliary substances and had a green color. Today, such a tool can also be found in stores and in the market. However, the production of green paste is currently prohibited and discontinued. The fact is that chromium oxide is a toxic carcinogen. Modern GOI pastes are white or red in color and are made of aluminum oxide. Using the second variety, polishing is faster. Using white paste, you can get a better and smoother surface.
GOI paste is a bar of light green or dark green color , consisting of an abrasive powder of chromium oxide, organic (fat) binders and excipients (activating and intensifying additives). GOI pastes are produced both in the form of bars, and in the form of soft (felt) polishing wheels already saturated with pasta. They are a mixture of chromium oxide (gives a green color, the hue of which depends on the percentage of 65-80%), as well as solvents and chemicals - kerosene, stearin, silica gel and others. There are 3 main varieties of GOI paste: coarse, medium (in the images) and thin (No. 1 and No. 2). Coarse has a light green color, is most effective for the removed volume of material, 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, used for fine grinding (lapping), give a mirror sheen.
Varieties of GOI pastes and their application
According to TU 6-18-36-85, four GOI paste numbers are distinguished depending on the size of the abrasive particles:
- No. 1 (black paste with a green tint; abrasive ability 0.3-0.1 microns) for fine polishing, give the treated surface a mirror finish. Composition: 65-70 parts of trivalent chromium oxide, 1.8 - silica gel, 10 - stearin, 10 - split fat, 2 - kerosene, 0.2 - bicarbonate (drinking) soda;
- No. 2 (dark green paste; abrasive ability 7-1 microns) for fine polishing, gives the treated surface a mirror finish. Composition: 65-74 parts of trivalent chromium oxide, 1 - silica gel, 10 - stearin, 10 - split fat, 2 - kerosene, 2 - oleic acid, 0.2 - bicarbonate of soda;
- No. 3 (green paste; abrasive ability 17-8 microns) for medium grinding, gives a clean surface without strokes and is used to achieve an even gloss of the polished surface. Composition: 70-80 parts of trivalent chromium oxide, 2 - silica gel, 10 - stearin, 10 - split fat, 2 - kerosene;
- No. 4 (light green paste; abrasive capacity 40-18 microns) for rough grinding, gives a matte surface and is used to remove the smallest scratches remaining 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.
A green variety was produced both in solid bars, and in the form of a more liquid pasty mass (in boxes). The popularity of both types is determined not only by the high quality of polishing, but also by more than an 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 a path of 40 m along a cast iron plate 400 × 400 mm.
|No.||Type of paste||Paste color||Abrasive ability, microns|
What to do before polishing
So, let's start to figure out how to use GOI paste. Small particles located in it, when rubbing the surface, remove a thin layer along with scratches and microcracks. Polishing is usually done with a soft cloth dipped in gasoline (can be from a lighter). A small layer of paste is applied to it and a little rubbed on an unnecessary piece of metal. This is necessary so that all too large pieces are broken in the paste. If they remain, the surface can not be polished, but rather scratched. The cloth should be really soft. You can take, for example, flannel. Sometimes the paste is applied to the polishing wheel. It is impossible to smear it directly on the surface of the workpiece. The product is pre-lightly smeared with liquid industrial oil ("spindle").
GOI paste: how to use
So, a rag with pasta is cooked. Now you can proceed directly to polishing. To do this, just rub the surface. In this case, do not press on the product too much. Otherwise, even more scratches may appear on it. For the same reason, too sharp movements of the hand should be avoided. Continue polishing until a completely smooth surface is obtained. From time to time, as necessary, a little “spindle” should be applied to the product.
How to polish with GOI paste objects with many deep defects? Usually in such cases, the surface is pre-treated with option No. 4. Then go to number 3. Finish processing No. 2, and the final gloss is induced by means No. 1.
After the operation is completed, you need to rinse the product in kerosene. The latter can be purchased at the pharmacy. If this does not succeed, it is allowed to rinse the polished object in running water. In some cases, the surface of the product after processing, rinsing and drying is additionally coated with a zaponlak. This can 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 cell phones into the "divine form". In this case, it will be necessary to polish, firstly, the case itself, and secondly, the display glass. Since plastic is a rather soft material, gentle paste from jars No. 2 should be used for its processing. Otherwise, the case can be scratched even more. The answer to the question of how to use GOI paste on plastic is simple: in the same way as when processing any other materials.
Glass is pre-polished with special rubber circles. Then use the GOI paste itself. The procedure in this case is the same, that is, using a rag. Oil and gasoline are not used when processing telephones.
How to use GOI paste for cleaning silver products
As already mentioned, this tool, both green, and red or white, can be used to process absolutely any metal. This also applies to silver. You can safely use GOI paste to lighten your spoons, cups and forks.
How to use GOI paste to clean silver? Before starting to polish, the product should first be thoroughly brushed with a toothbrush with tooth powder applied to it.
Then pour a little ammonia into a glass of water, make soap and pour a little powder. All this must be thoroughly mixed until completely dissolved. Next, the liquid is poured into some enameled saucepan. After that, silver cutlery is lowered into it. Then put the saucepan on the fire and bring the liquid to a boil. After that, the silver should be removed and washed in cold water. Then you can start processing it with GOI paste according to the method described above.
What can not be polished
Next, let's see in which cases GOI paste cannot be applied. How to use it, you now know. However, in no case should you use this tool for processing gilded things. Otherwise, the upper valuable layer will be very quickly erased to the lower metal. Steel (except for knives) and nickel are usually not processed manually, but using a special machine. Polishing metal watches is also done with a cloth. However, they must first be disassembled and the mechanism pulled out. You can not start polishing too much scratched surfaces with option number 2 or 1. In this case, the defects will become even more noticeable. The sapphire crystal on the watch cannot be polished with GOI paste. She simply does not take them.
Where is the product used
With how to polish paste GOI, we figured out. Now let's see where exactly 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 most often used in galvanic shops for processing products from non-ferrous and ferrous metals. Polishing is carried out using special polishing machines with felt circles.
Today on sale you can also find imported versions of such pastes. A very popular option is the French Dialux. The latter is characterized by a more solid consistency and is worse applied to the skin of the bar when sharpening knives than GOI paste. Dialux is considered more convenient to use. It is possible to polish metal surfaces with it much faster and better. However, such pastes are more expensive. There are much more varieties of Dialux than types of GOI. This product is available in sticks packed in paper of different colors. According to them, you can navigate in terms of using Dialux for a particular metal.
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