Badges, brooches, ornaments and many items are covered by enamel - glass deposited on the metal. Here we will try to make the glass. For these experiments required a special oven. For this reason the manufacture of glass you cannot do at home. But, in addition, you need the skills to work with hot melts, so that the experiments we have carried out in the presence of elders.
On the plants and in the chemical laboratories of the glass produced from the mixture is thoroughly mixed dry powder mixture of salts, oxides and other compounds. When heated in the furnace up to very high temperatures, often above 1500°C, the salts are decomposed to oxides, which interact with each other, form the silicates, borates, phosphates and other stable at high temperatures connections. Together they make up the glass.
We will prepare the so-called low-melting glass, which is enough for laboratory electric furnaces with temperature up to 1000°C. Still need crucibles, crucible tongs (not to burn yourself) and a small flat plate, steel or cast iron. We first brewed glass, and then find a use for it.
Stir with a spatula on a sheet of paper 10 g of sodium tetraborate (borax), 20 g of lead oxide and 1.5 g of cobalt oxide, sifted through a sieve. This is our charge. Pour it into a small crucible and sealed with a spatula to make a cone with the vertex at the center of the crucible. The densified mixture should occupy in the crucible of not more than three quarters of the volume, then the glass will not spill. Using the tongs, place the crucible in the furnace (crucible or muffle), heated to 800-900 °C and wait until the charge will not merge. About it is judged by the selection of the bubbles as soon as it stopped, the glass is ready. Remove the crucible with the tongs from the oven and immediately pour the molten glass on a steel or cast-iron stove with a clean surface. Cooling down on the stove, the glass forms a wedge of blue-violet color.
To get the glass of other colors, replace the cobalt oxide other coloring oxides. Iron oxide(III) (1-1,5 g) stained glass in brown, copper oxide(II) (0.5-1 g)-green, a mixture of 0.3 g of copper oxide with 1 g of cobalt oxide and 1 g of iron oxide (III)-black. If we take only the boric acid and lead oxide, the glass will remain colorless and transparent. Try it with other oxides, for example, chromium, manganese, Nickel, tin.
Glass grind with the pestle in a porcelain mortar, to avoid splinters, be sure to wrap a hand towel, and a mortar with pestle cover with a clean cloth.
Ssypte fine glass powder on the thick glass, add a little water and stir to a creamy state curenton - glass or porcelain disc with handle. Instead courante you can take a small flat-bottomed mortar or polished piece of granite - so did the old masters, when rubbed paint. The resulting mass is called the slip. It will be applied on the surface of aluminum is about the same as doing it, manufacturing jewelry.
Clean aluminum surface with sandpaper and degrease the boiling soda solution. On a clean surface will draw a scalpel or a needle loop of the figure. Surface using the normal brush cover slip, dry over the flame, and then heat in the same flame as long as the glass does not napravite on the metal. You get enamel. If the icon is small, it can be covered with a layer of glass and heat it in the flame entirely. If a product is larger (say, a tablet), you have to split it into parts and put the glass on them. To color enamel was more intense, apply the glass again. This way you can receive not only decoration, but also a reliable enamel coating to protect the aluminum parts in all kinds of devices and models. As in this case, the enamel shall bear the additional load, the metal surface after degreasing and washing, it is desirable to cover a dense oxide film; it is enough to hold the item for 5-10 minutes in the oven with a temperature below 600°C.
Of course, for the most part the slip easier not apply with a brush, spray or just watering (but the layer should be thin). Dry the item in an oven at 50-60°C, and then migrate in the electric furnace, heated to 700-800°C.
The low-melting glass can be prepared colored plates mosaic. Pieces of broken crockery (you will always give in a China shop) pour a thin layer of slip, allow to dry at room temperature or in a drying Cabinet and naplate glass on the plate, soaking them in an electric furnace at a temperature of not lower than 700°C.
Having mastered working with glass, you can help your colleagues from biological mug: there often produce stuffed animals and stuffed the desired colored eyes...
In the steel plate thickness of about 1.5 cm drill several holes of different sizes with a conical or spherical bottom. In the same way as before, alloy colored glass. Gamma, perhaps, enough and to change the intensity, slightly increase or decrease the content of coloring additives.
A small drop of bright molten glass is put into a hollow steel plate, then pour in the glass the color of the iris. The drop will be included in the bulk, but will not mix with it, so will be reproduced and the pupil and iris. Cool products slowly, avoiding sudden temperature changes. This solidified but still hot "eye" remove from the mold heated tweezers, put in a friable asbestos and have it cool to room temperature.
Of course, low-melting glass can be found and other applications. But isn't it better if you look for them yourself?
And at the end of the experiments with glass, using the same furnace, will try to turn ordinary glass into a color. A natural question: is it possible in this way to make sunglasses? You can, but this is unlikely to be able to you the first time, because the process is capricious and requires some skills. Therefore, grasp the points only after practice on pieces of glass and ensure that the result meets expectations.
Based paint for glass is rosin. From resinates, salts of acids, forming part of the rosin, you previously prepared driers for oil paints. Again refer to resinatum, because they can form on the glass thin even film and serve as carriers of the coloring matter,
In caustic soda solution of concentration about 20% of tiredness while stirring and keeping in mind, of course, be careful, pieces of rosin until then, until the liquid becomes dark yellow. Filtering, add a little solution of ferric chloride FeCl3 or other salts of trivalent iron. Keep in mind that the concentration of the solution should be small, salt can not be taken in excess - precipitate of iron hydroxide, which in this case is formed, we hurt. If the salt concentration is small, it produces a red precipitate of resinate iron - he is there and needs.
Filter red precipitate and dry it pas the air, and then dissolved to saturation in pure gasoline (no car, and gasoline-solvent) even better would be to take hexane or petroleum ether. With a brush or spray paint the glass surface with a thin layer, let dry and put on 5-10 minutes in a furnace heated to about 600°C. But rosin refers to organic substances, and they are such a temperature not survive! Right, but that's what it takes - even organic basis will burn out. Then, the glass will remain thin film of iron oxide, inched to the surface. Although the oxide is generally opaque, so thin it skips part of the light rays, i.e., can serve as a filter.
May the light shielding layer will seem too dark or too bright. In this case PowerLite conditions experience little increase or decrease the concentration of the solution of rosin, change the time and temperature of firing. If you are not satisfied with the color that brightened up the glass, replace the ferric chloride chloride of another metal, but certainly such, the oxide of which are brightly colored, such as copper chloride or cobalt.
And when the technology is thoroughly tested on pieces of glass, it is possible without too much risk to make the transmutation of common points in the sun. Do not forget to remove the glass from the rim plastic frame will not stand the heat in the oven just as rosin base...