The advantage of this firebox size is that it can better concentrate the firewood temperature at the central point, thereby achieving a high fuel efficiency.

Therefore, this type of stove is also called a firewood-saving stove in rural areas. However, the stove has only one drawback: it cannot be left unattended while the fire is burning.

Because the fuel inlet is small, not much wood can be put in, which means that people have to add firewood from time to time.

This isn't a problem for me right now; in fact, it's quite relevant to my current situation. By making the best use of firewood, I can significantly reduce the time I spend searching for it.

To create a relatively flat furnace bridge, I first used a thin hemp rope to measure the inner diameter of the furnace chamber.

Next, a large lump of clay was taken out, and some sand and calcined clam shell powder were added and kneaded until evenly mixed.

The main component of sand is silicon dioxide, while the calcined clam shell powder is calcium oxide. These two components make the furnace bridge stronger and more durable.

I placed the kneaded clay on a banana leaf, and then used my hands to roll it out evenly into a large clay cake that was more than 30 centimeters wide and 1 centimeter thick, just like rolling out dough.

Next, use the thin hemp rope to measure the size. Just make sure the mud cake fits inside, and cut off any excess with the rope.

Then comes the drilling.

Here I simply used my own fingers. I moistened my index finger with a little water to lubricate it, and then I evenly poked holes into the mud cake.

The furnace bridge is now temporarily complete; it needs to be placed inside the furnace.

The furnace bridge is still very soft at this moment. If it is put in directly, it will definitely collapse under its own weight.

Therefore, bamboo strips are needed to bridge the furnace first. Specifically, bamboo strips of appropriate length are laid out in one direction to create a flat platform.

Then carefully pick up the banana leaf and stove bridge and place them on the bamboo bridge that has been set up.

After completing this step, I continued mixing the clay. I rolled the clay into thick strips, then connected and stacked them layer by layer.

The joints between the upper and lower layers of mud strips should ideally be staggered, just like when laying bricks, the upper and lower layers of bricks are connected in an offset manner. This will result in much greater strength than a symmetrical connection.

I stopped working when the mud had been piled up to about half a meter high, because I couldn't continue piling it up.

Soil is soft; if the top layer is piled up too high, the weight of the soil itself will cause the soil below to collapse.

So what I need to do now is to light a fire in this semi-finished clay brick to dry the clay around the sides and bottom a bit, so that it can support the weight of the clay on top and prevent the entire furnace from deforming.

There are certain techniques to starting a fire. You can't make the fire too big at the beginning. If the fire is too big and the temperature is too high, it will crack the clay bricks. In particular, the furnace bridge should not be fired with a strong fire.

I lit some thin firewood and put it into the firebox, then slowly added more firewood, trying to keep the temperature from getting too high.

This method for testing stable temperature is also very simple. Just place your hand above the flames of the fire. It should feel just slightly hot to the touch, but not too hot.

As the flames rose, steam began to rise from around the clay. I continued to control the temperature of the flames, keeping them baking the clay.

Half an hour later, the furnace bridge inside was dried out and turned yellow.

Seeing that the stove bridge had dried out, I added a pile of thin firewood on top of it and lit it, which, together with the firewood in the stove, baked the stove bridge to make it even harder.

Another half hour passed, and by then the soil at the bottom was almost dry. I gently poked the lower half of the clay and felt that it had reached the desired hardness.

So I started rolling out clay strips again, continuing to build up the outer wall of the kiln. This work was relatively simple; as long as you were careful, there shouldn't be any problems.

And so I repeated this task. I didn't stop until the overall height of the structure was about 1.6 meters.

The kiln height is about right now; continue drying the clay blanks on top.

Once the top layer of clay had dried to the appropriate degree, I used a wooden stick to make a hole about the size of a sausage about ten centimeters below the very top of the clay.

Next is the construction of the gas recirculation system for this kiln.

In a civilized society, I would probably use metal pipes to do this step, but I don't have those now, so I have to use another method to solve this problem.

I took out the thin bamboo strips I had prepared beforehand, compared them to the position of the hole I had made, and then made a circle of the right size.

The next step is to weave a hollow, tubular skeleton structure, which is not too difficult with previous weaving experience.

In a short time, I wove a pipe structure that was nearly 1.5 meters long using bamboo strips.

Then I started kneading the dough again, this time it needed to be a bit firmer. Ideally, it should be the consistency of dumpling dough.

The advantage of a bamboo tube frame woven from bamboo strips is that the mud coating can be slightly embedded in the mesh of the bamboo strips, increasing the adhesion of the mud and preventing it from falling off easily.

After finishing the hollow clay tube, I set it aside for the time being. Next, I drilled a hole of the same size on the outer wall of the furnace chamber, which was aligned with the hole above, leading directly into the furnace chamber.

These two holes are located in the gas recirculation system that connects the inside of the kiln to the bottom firebox.

The operating principle is that when the fire below is lit, it heats the wood inside the kiln via the furnace bridge. Because I also need to make a large mud lid on top, the wood inside the kiln is carbonized by dry distillation in an oxygen-deficient environment.

The furnace temperature is extremely high during the carbonization process, which produces a large amount of flammable smoke, much like the white smoke produced when a candle is blown out. This smoke is also very flammable.

The purpose of that pipe is to recover the combustible gas inside the kiln and return it to the firebox for secondary combustion.

This has two advantages: firstly, it avoids producing smoke that could nearly kill you; secondly, it fully utilizes the energy of all the wood, making the most of everything and wasting nothing, including the smoke.

I carefully picked up the jungle-style pipe and slowly inserted it into the hole above. Then I used mud and water to seal the gaps in the hole.

The same procedure is followed for the lower hole. The gap between the joints is sealed with mud, and the entire reflux system is complete.

The last thing to do is the clay lid I mentioned for sealing the top, which is also the most difficult component to make in the whole process.

The quality of the seal also determines the quality of the charcoal, so extra care must be taken when making this last component.