The market offers a large selection of thermoses, varying both in volume and price. Why make homemade? Even high-quality factory products sometimes fail, and at the most inopportune moment.
You are about to put a thermos in your backpack when you find that the outer bulb has warmed up. This is a sure sign of violation of thermal insulation properties. Have to craft it from improvised means!
How to make a thermos
Let's see how factory products are arranged. Their design complicates the heat transfer of the stored object with the external environment. Body temperature is related to the rate of vibration of its molecules.
Heat can be transmitted either by the collision of molecules (thermal conductivity), or by infrared radiation.
Modern thermoses work on the principle of a Dewar vessel, invented in the late 19th century. They consist of two metal vessels inserted one into the other, between which air is evacuated. The metal surface reflects infrared radiation, and the vacuum provides low thermal conductivity.
Our home-made thermos is also based on the Dewar design, only instead of vacuum there will be a heater, and instead of metal vessels there will be plastic bottles. To reflect infrared radiation, we use a household aluminum foil, in which we wrap an inner vessel.
A key element in the design is insulation. What can be used as a heater:
- Free newspapers with advertisements;
- Polystyrene crumb;
- Polyurethane foam;
- Polyurethane foam;
- Wood shavings;
- Toilet paper, etc.
The simplest insulation can be balls from pieces of free newspapers. The lack of newspapers is the poor tolerance of contact with water. Sources of foam: packaging for household appliances, trays for vegetables. It is easy to make crumbs out of it.
Rolled polyurethane foam is also used as packaging material. Sold in hardware stores. Polyurethane foam is the same polyurethane foam, but in an aerosol can. Almost ideal material, however, it has an unpleasant property: it expands so much that the inner vessel can deform, and if a glass bottle acts in its role, it will burst. Plastic must be pre-filled with water so as not to lose shape.
Attention! Glass bottles should not be combined with polyurethane foam.
The main criterion for choosing a heater is the presence of a particular material. We assume that the design is disposable (or close to that) and the manufacturing costs should be minimal.
Inner vessel material
The advantage of a thermos of two plastic bottles is the phenomenal impact resistance. They can even play football. This is where the virtues end. Do not pour boiling water into a plastic bottle.
Firstly, it is deformed, and secondly, harmful substances are released. The maximum water temperature should not exceed about 80 degrees.
To compensate for this drawback, you can use a glass bottle. Pouring boiling water into it is better in two stages. First pour a small amount and shake, and then add the remaining amount. Otherwise, it is likely that it will burst.
- Take two plastic bottles with relatively thick walls: per liter and per liter, or 1.5 and 3 liters. It is better to choose the inner one with a long narrow neck. It is more beneficial for thermal insulation.
Important! Thermos from plastic bottles is intended only for cold drinks.
- At the outside, carefully cut the neck with a knife. The diameter of the resulting hole should be slightly smaller than the cork of the inner bottle. Then we make small longitudinal cuts so that the inside comes in tight.
- The outer bottle is cut into 2 parts just below the middle. Cut at a slight slope to the axis of symmetry. So the cut parts are easier to fit into each other during assembly.
- Wrap the inner bottle with foil. We fix it with adhesive tape.
- Insert the inner bottle into the top of the outer one.
- We fill the internal volume with insulation. The easiest way to do this is when it is crushed into small pieces (in the case of newspapers, roll the scraps into balls), or when using polyurethane foam.
Important! The insulation must be tamped, otherwise the inner bottle will hang out and scroll relative to the outer one.
- We insert the parts of the outer bottle into each other and glue them with tape.
- We glue the exit point of the neck of the inner bottle so that water does not get into the insulation zone.
- Assembly completed. It remains to test.
A thermos on the basis of bottles of 1 and 3 liters with a heater from newsprint balls was filled with water at a temperature of 80 degrees and placed in frost.
After two hours, the temperature dropped to 40 degrees. We can conclude that a home-made thermos keeps heat about 9 times worse than an unnamed Chinese.
Suppose you only have a 0.5 liter bottle. Wrap it with foil. We put on two down socks or wrap it with a woolen scarf. We put on a black plastic bag and glue it with tape. It turns out a thermos from the series "better than nothing."
What you need to make a thermos
- For the first design:
- A pair of plastic bottles (0.5 and 1, or 1.5 and 3 liters);
- Aluminium foil;
- Insulation (see above);
- A knife is advisable.
- For the second design:
- Bottle 0.5 L;
- Two down socks or a wool scarf;
- Black bag;
- "Thermos" from a flask
If you have a small flask for alcoholic drinks, then in winter it can serve you as a good thermos. The volume of such flasks rarely exceeds 250 ml. However, when thirst overcomes, then even a glass of water can significantly ease your position.
Pour into a flask of warm water, but not boiling water, so as not to get burned. We put it in the pocket of a shirt or vest with a large number of pockets. We put on a sweater and a winter jacket from above. Due to the flat shape, hidden wearing does not cause any problems. The temperature of the water will be constantly equal to the temperature of your body, which in the cold season is very good. Warm up will not work, but you quench your thirst easily.
Important! Before use, make sure that the flask does not leak.
We found that it is not so difficult to make a primitive thermos at home, but such structures are significantly inferior to industrial designs in terms of heat-insulating properties. It is advisable to produce them only if there is no opportunity to purchase a factory product.