The creation of glass is an ancient process, there is archaeological evidence on the glass art that dates back to 2500 BC. It was once a rare and precious art, but today glass making is part of the common industry. Glass products are used commercially and in the home in the form of containers, insulators, reinforcing fibers, lenses and decorative items. While the material they are made of can change, the process of making the glass remains the same and is described in this guide.
Steps
Method 1 of 2: Using a Furnace or Oven
Step 1. Obtain silica sand
Also called quartz sand, silica sand is the primary ingredient in glass making. Glass without ferrous impurities is required for clear glass pieces, as iron makes it greenish.
- Wear a mask if you use very fine silica sand. If inhaled, it can irritate the throat and lungs.
- Silica sand can be bought online. It is quite cheap, small quantities are around € 15. If you want to work on an industrial scale, specialized sellers will offer you competitive prices for large orders, sometimes less than € 70 per ton.
- If you cannot find silica sand free of ferrous elements, the coloring effect can be counteracted by adding small amounts of manganese dioxide. Otherwise, if you want to get greenish glass, don't remove the iron!
Step 2. Add sodium carbonate and calcium oxide to the sand
Sodium carbonate (commonly called soda) lowers the temperature needed to make commercial glass. However, it allows water to pass through the glass, so that calcium oxide or lime is added to negate this property. Magnesium and / or aluminum oxide can also be incorporated to make the glass more resistant. Usually, these additives take up no more than 26-30% of the glass mixture.
Step 3. Add other chemicals, depending on the destination of the glass
The most common addition to decorative glass is lead oxide, which provides sparkle to crystal glasses, as well as the softness needed to cut the glass more easily and lower the melting point. Prescription lenses may contain lanthanum oxide for its refractive properties, while iron helps glass absorb heat.
Lead crystal can contain up to 33% lead oxide. The greater the amount of lead oxide present in the glass, the more skilled you need to be to shape the molten glass, so many manufacturers opt for a lower lead content
Step 4. Add chemicals to produce the desired color if you want tinted glass
As we mentioned earlier, ferrous impurities in quartz sand make the glass greenish, so iron oxide is added to increase the greenish tinge, as is copper oxide. Sulfur compounds produce yellow, amber, brown or even a blackish tint, depending on how much carbon or iron is added to the mixture.
Step 5. Put the mixture in a good crucible or heat resistant stand
The container must be able to withstand very high temperatures inside the oven; depending on the additives you have chosen, the glass mixture can melt between 1,500 ° C and 2,500 ° C. In addition, the container must be easily handled with metal hooks and poles.
Step 6. Dissolve the mixture to make it liquid
Commercial silica glass is melted in a gas oven, while specialty glasses can be created using an electric melting furnace, pot oven, or oven.
Quartz sand without additives becomes glass at a temperature of 2300 ° C. The addition of sodium carbonate (soda) reduces the temperature needed to make glass to 1,500 ° C
Step 7. Stir and remove bubbles from the molten glass
This means stirring the mixture until it is thick and adding chemicals such as sodium sulfate, sodium chloride or antimony oxide.
Step 8. Shape the molten glass
It can be done in many different ways:
- The molten glass can be poured into a mold and allowed to cool. This method was used by the Egyptians, and this is how a large number of lenses are still created today.
- A large amount of molten glass can be collected at the end of a hollow tube, which is then blown as the tube is turned. The glass is shaped by the air entering the tube, by the gravity that attracts the molten glass and by the tools used by the glassmaker to work it.
- Molten glass can be poured into a molten tin bath for support, then blasted with pressurized nitrogen for modeling and polishing. Glass created with this method is called float and this is how glass sheets have been made since 1950.
Step 9. Heat the glass to strengthen it
This process is called annealing, and is used to remove any stress points that may form in the glass during cooling. Glass that has not been annealed is significantly weaker. Once this process is completed, the glass can then be coated, laminated or otherwise treated to improve its strength and durability.
- The precise temperature for annealing can vary according to the composition of the glass, from 400 ° C to a maximum of 500 ° C. The speed at which the glass has to cool can vary: usually large pieces of glass cool more slowly than smaller pieces. Do proper research on annealing methods before starting.
- A related process is tempering, in which the shaped and polished glass is placed in an oven heated to at least 600 ° C and then rapidly cooled ("off") with high pressure air jets. Annealed glass breaks into fragments with 240 kg per cm² (pa), while tempered glass breaks at no less than 1000 pa and usually around 1680 pa.
Method 2 of 2: Using a Charcoal Barbecue
Step 1. Prepare an improvised oven from a charcoal barbecue
This method uses the heat generated by a large coal fire to turn the silica sand into glass. The materials used are relatively cheap and common; in theory, you should find everything you need in the nearest hardware store. Use a large barbecue; the dimensions of the standard "dome" model are fine. Use the thickest and strongest grill you have. Most barbecue grills have a vent on the bottom that needs to be opened.
- Despite the extremely high temperatures achieved with this method, silica sand is difficult to dissolve on a grid. Before starting, add a small amount (about 1/3 or 1/4 the volume of the sand) of soda, lime, and / or borax to the sand. These additives lower the melting temperature of the sand.
- If you are going to blow glass, have a long, hollow metal tube handy. If you are going to pour it into a mold, prepare it in advance. Make sure the mold does not burn and does not melt with the heat of the molten glass; graphite works well for this purpose.
Step 2. Learn about the dangers of this process
This method will push a traditional barbecue beyond its normal limits; the temperature will be so high that even the grill itself could melt. There is a risk of running into serious injury or death if you do not operate with extreme caution. Have a fire extinguisher or a large amount of dirt or sand on hand to smother the fire if necessary.
Step 3. Take every possible precaution to protect yourself and your property from high heat
Try this method on an outdoor concrete surface with plenty of space. Do not use any irreplaceable equipment. It is necessary step away from the grill while the glass heats up. It would also be best to wear as much protective clothing as possible, including:
- Heavy oven gloves or mittens
- A welder's mask
- A heavy apron
- Heat resistant clothing
Step 4. Get a blower vacuum cleaner with a long hose attached
Using duct tape or another method, angle the hose so that it blows directly into the vent on the bottom of the barbecue, without touching the main body of the grill. It is recommended to attach the hose to one of the barbecue legs or wheels. Keep the body of the vacuum cleaner as far away from the heat source as possible.
- Make sure that the tube is fixed well and that it does not move; if it comes off while you are creating the glass, Not you have to get close to the barbecue if it is very hot.
- Turn on suction to test tube placement. It should blow directly into the ventilation holes.
Step 5. Line the inside of the barbecue with charcoal
Use more charcoal than you would use for grilling meat. Positive results have been achieved by filling the barbecue almost to the brim. Place a cast iron pot or crucible with sand in the center, surrounded by charcoal.
Hardwood (or "block") charcoal burns gives more heat and is faster than charcoal briquettes; use it for this project if you can get it
Step 6. Ignite the charcoal
Check the directions on the package to find out if it can be ignited directly or if a flammable liquid is needed. Let the flames spread evenly.
Step 7. Wait for the coal to heat up
When the charcoals are grayish and give off an orange glow, they're ready. You should be able to feel the heat by simply standing next to the grill.
Step 8. Turn on the vacuum cleaner to blow air over the charcoal
When coal is fed with air from the bottom it can reach very high temperatures (up to 11000 ° C).) Be very careful as there may be sudden flare-ups.
If you are still unable to get hot enough, try replacing the lid as you introduce air through the vent
Step 9. When the glass is melted, use metal tools very carefully to remove and shape it
Due to the relatively low temperatures achieved with this method, molten glass can be stiffer and more difficult to process than furnace-melted glass. Shape it with a tube, mold, or other tools as you normally would.
Advice
- If the sand or additives are coarse, pulverize them with a mortar and pestle or with a mechanical grinder. The finer particles dissolve faster.
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Pieces of old crushed glass can be added to the sand before melting to be recycled into new glass. Old glass must first be checked for impurities that would weaken the new glass, even creating bubbles.
When sanding the glass, wear a face mask to prevent accidental inhalation
- Some beach sands can be used in place of pure silica sand, although the resulting glass can be opaque, discolored, or of lower quality. Use the whitest, finest and most uniform sand you can find.
Warnings
- you do always pay attention to heat sources. Never try to create glass in the presence of children or pets.
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Extinguishing very hot fires with water can make the situation worse. For example, a fire burning at 2,000 ° C is hot enough to split water (H2O) into hydrogen and oxygen atoms, releasing an enormous amount of heat energy. For very hot fires, it is best to keep a large bucket of earth or sand close at hand.
Class D fire extinguishers contain sodium chloride (table salt) and are used to smother fires caused by metals
