The backlog eventually has to be cleared. This series is supposed to appear at most once a week—and not reliably even then; it depends on whether an idea stays active long enough to become a post. Lately the ideas have not been cooperating. Writing stalls the same way fiction does: for a while there were more angles than I knew what to do with, then the well went quiet. Time for actual typing has also been squeezed, so anything that gets written happens in the gaps.
So here is a useless installment. There has not been much technical trouble worth documenting lately. When there is, I usually let an LLM handle it—like an LLM API switcher I vibe-coded. The middle of that process was not interesting. My skills are not enough to build or investigate something that nobody else has, so I fill the space with other things.
How to be useless
The urge to tinker showed up early. In primary school, no later than 2015, every summer I started plotting ways to make something cool. There were already ways to cool down—that was not the point. I had to make something with my own hands. Looking back, I kept circling the same three projects: a homemade air conditioner, a homemade fridge, and homemade ice cream. I might as well call them the homemade cooling trio.
Summer vacation was long, the days were idle, and none of these projects were especially dangerous—at least compared with electric heaters or random chemistry experiments. My family did not object. Sometimes they even bought materials for me. I had no allowance then, so the whole operation was funded at home. I remain grateful for that support.
I no longer remember how I first encountered these three ideas. Youku, maybe? The internet back then could still turn up a lot. Once I learned that a person could make their own cold air, I searched videos, image posts, and forum threads, trying to see how other people did it and whether I could copy them.
Homemade air conditioner
A child had no money or ability for a compressor air conditioner, and semiconductor cooling seemed too complicated. Then a CCTV program, Is It True?, ran an episode that gave me an idea: a foam box filled with dozens of frozen water bottles, plus a USB fan, supposedly cooled a small room. The fancy term was ice-storage air conditioning. Really, it just used frozen bottles as the cold source.
There were many ways to build one. A fan could blow across ice inside a foam box—the television version, sometimes scaled down. Copper tubing could be coiled in front of a fan with chilled water running through it. A ready-made heat exchanger and a pump could be used. DIY builders kept producing new versions, and I tried the ones I could. If a material was at home, I used it. If not, I substituted. The foam box came from a seafood vendor at the market. The fan was a spare 12V computer fan running off a battery, which felt safe enough for my family. Copper tubing was unavailable, so I used plastic tubing from a nebulizer.
Anyone who has watched those videos can probably guess where this ended: either the air was not cold enough, or it was not cold at all. My understanding of energy was shallow. I assumed that “colder” meant “lasts longer,” forgetting that the box needed a serious mass of ice—the television setup used a whole box of frozen bottles—and a fan strong enough to move air through it. This was not real refrigeration, either. It could not continuously move heat somewhere else. Once the ice melted, it had to go back into the freezer. The whole thing depended on how well the home freezer worked. Replacing copper with plastic tubing was another bad idea. Plastic transfers heat poorly, so an already weak cooling setup became weaker. Even the original version was not going to perform miracles.
Homemade fridge
If the ice-bottle route were turned into a box, it would actually work as a fridge. But that felt too simple. Search for “homemade fridge” and the results were dominated by Peltier cooling plates. Conveniently, online shops sold ready-made semiconductor cooling modules with heatsinks and fans on both the hot and cold sides. I ordered one happily. Power was the issue: a Peltier plate draws a lot, sixty or seventy watts each, far too much for the small battery I used for play. I found an abandoned ATX power supply, added a switch between the green and black wires, and it lived again.
This attempt went slightly better. I put the cold side into a foil-lined foam box. On a hot day, the inside could drop to around 12°C. That was obviously not as cold as the fridge at home. Drinks—or a water cup, since my family did not let me drink much soda—were not properly chilled, and drinking them was not satisfying. It was certainly not a real fridge. So I went back online for videos and articles, trying to improve it without spending much money. Tools were lacking, my workmanship was poor, and I often fixed one problem only to create another. The results were not good. Among the things I tried:
- A smaller foam box: the most effective change, but not by much.
- A plastic airtight box: lined with foil, with the foam box inside, to improve insulation. The effect was not obvious.
- A bigger fan on the cold side: too big. The air left before it had time to cool.
- Swapping the cooling plate and heatsink: none of the heatsinks I had fit. Failure.
- Moving the module from the side to the top: somewhat useful, but condensation quickly became a problem.
Condensation was especially annoying. It dripped onto the fan, leaked out through the side opening where the module sat, or pooled inside the foam box and eventually turned moldy and smelly. The homemade fridge never became a success. I never stored anything proper in it. I later saw a buyer review from someone using one to keep dog food cool; according to that person, it was sufficient.
In the end I stopped building boxes. I placed the cooling module upright and put a stainless steel cup on the cold heatsink, filled with cooled boiled water. After about ten minutes, part of the water froze, and I could enjoy cold water.
That trick is essentially the principle behind some cheap hot-and-cold water dispensers. The “cold tank” is a Peltier cooler. Once powered, it chills a small container of water and shuts off when the temperature is low enough. Because the power is modest, it cannot supply cold water continuously; after a few disposable cups, it runs out. Compressor-based dispensers sit above that: better cooling, more cold water, higher price, and therefore less common. Plenty of dispensers on the market only offer hot and room-temperature water; the right-hand tap is connected straight to the tank.
Homemade ice cream
This should have been the least technical and the most pleasant, because the result is sweet and edible. My family did make summer treats, but ice cream was missing. The closest thing was ice pops made by freezing mung bean syrup in molds. The texture was nowhere near ice cream. One summer I got curious and decided to make ice cream myself.
I started with online recipes: milk, sugar, and egg yolk, with the yolk as a thickener; some recipes added cream. In practice, I do not know whether the method was wrong—one recipe wanted stirring every hour, and I probably did not have the patience—or the quantities were off, or the freezer temperature was wrong. The result was either hard as a popsicle or refused to set for a long time. The egg taste was too strong. It did not resemble ordinary ice cream at all. Much later I bought a packet of ice cream powder at the supermarket and followed the instructions. That produced something that could at least be called ice cream, but the flavor was strange: milky, yet hard to describe. Maybe some ingredients had been compromised to make the powder. I do not know.
According to the internet, a real ice cream machine makes a difference. A self-freezing compressor model is better, but even the most basic kind—the one with a bowl you pre-freeze in the freezer—beats hand mixing. The secret is continuous stirring. Some machines also have a special paddle that introduces a lot of air while the mixture chills, helping it expand and set. There is a manual bag method too: a small bag for the ice cream mixture, a large bag for ice and salt, and a lot of shaking. You put the mixture in the small bag, leave some air, seal it, put it inside the large bag, pack ice and salt between the two, seal the large bag, and shake continuously. The motion aerates the mixture while the salted ice chills it. I have not tried this because it sounds like a hassle. If anyone has tried it and found it useful, I would not mind hearing about it.
Youku, when it was casual
The heading is odd, but here is what I mean. Around 2010, Youku was already popular. I remember a video of someone using a blurry camera to film a row of satellite dishes on a residential balcony. No editing, no narration, shaky footage, and Eason Chan’s “Ten Years” playing from beginning to end.
The internet felt simpler then. People shared things because they wanted to share them, and videos with almost no editing were common. I was interested in satellite antennas, so I saw quite a few. One example: the owner of an electronics shop, probably in the urban-rural fringe, had someone film him while he explained and assembled a satellite television reception system—a knockoff first-generation Zhongjiu Huhutong. The whole thing was one take, ending when the picture finally appeared. On today’s video platforms, a clip like that would probably need a “shocking” opening, a “what do you think?” ending, an inexplicable AI voice, abstract graphics overlaid on the screen, mysterious sound effects, and, of course, an ad break with some mysterious woman in glasses.
There was another category on Youku. I do not know if it was a coincidence, but typing “牛人自制”—“master homemade”—into the search box brought up a large number of videos reposted from YouTube. Homemade generators, homemade wood stoves, maybe homemade air conditioners, “master makes a Jiangnan Style comic,” “street master makes a drum kit.” Some were translated, some were not. I watched many of them and lost track of how many times I was amazed that such people existed and were doing such things.
Youku stopped focusing on user-generated content long ago. Those early videos are probably gone and impossible to find. The links I would give now are on Bilibili, but the videos are the same and can still be watched there.
Creamer and powdered sugar
New things did not only appear on the internet. Around 2010, before several revamps of CCTV7’s Nongguang Tiandi, the program aired an episode called “Tea Beverage Mixing Techniques.” It introduced several tea drinks. One was “milk black tea.” The method was not difficult: brew lapsang souchong, pour it into a cup, add non-dairy creamer and powdered sugar, and it was done.
Milk tea was rarely allowed at home then, so the “milk black tea” segment stuck with me. I knew tea. But what were “creamer” and “powdered sugar”? I had never heard of either. I do not remember why I did not look them up. Maybe I was lazy. Maybe the television only showed a few shots, and I suspected I had misheard “milk powder” and “saccharin.” Both of those were familiar. I had drunk milk powder as a child, and my family used saccharin; it was very sweet and worked well with certain sour fruits.
Later I learned that non-dairy creamer really exists, and that milk powder and creamer are completely different. Milk powder can be made from fresh milk. Creamer, whose formal name is vegetable fat powder, is plant fat plus glucose syrup and other processing. Why anyone invented it depends on whom you ask. One account says people wanted a coffee additive that stored well and had a consistent flavor. Another says it was made to comply with certain religious rules—dairy and meat should not be eaten close together. Either way, the result was a product called cream that contains no milk.
Powdered sugar needs less explanation: it is white sugar that has been ground into powder. It is used in milk black tea because it dissolves quickly. Because it absorbs moisture readily, it is rarely used in daily cooking and usually comes in small single-serving packets.
Creamer is not very nutritious. The video also mentioned that fresh milk could be added instead, though I thought that would dilute the tea. As a child, I had never seen or tasted creamer, so I was fascinated by it. The same applied to the drinks section in a kindergarten textbook, which mentioned “Guozhen” and “Gaolegao.” I had never heard of those either, so I longed to try them. When I finally did, years later, the result was... fine. Not disappointing enough to matter, but after that the curiosity was gone.
That is another one cleared. The new tinkering target: the first book in the Fenglin Bookstore is entirely manuscript pages, so I have been working out a simple, fast way to handle OCR and manual correction. If it comes together, I will write it up separately. For now, I will leave it there.