1. How gas went from lighting to heating and cooking in the 1890s
Gas flames began as lighting. In the 1890s (Meiji 30s), usage expanded to heating and cooking [1]. A device called the "dual-use gas lamp" shows this change. It had a branch in the pipe leading to the ceiling gas lamp, allowing a stove to be connected [1]. A newspaper ad from 1902 shows people gathered around a pot lit by this lamp, alongside a "gas kamado" (gas stove) released that year [1]. Lighting and cooking shared the same gas pipe. The flame was still used for both lighting and cooking.
2. How Japan's first patented gas appliance, the gas kamado, differed from wood stoves
The "gas kamado" developed in 1902 was Japan's first patented gas appliance [2]. Improved models appeared in catalogs in 1908 and are still used in some traditional restaurants today [2]. Its appeal was the difference from wood-burning stoves. Gas stoves and gas kamado produce no soot or smoke, and adjusting the heat is easy [3]. In the 1930s, they were part of the "ideal clean kitchen." It is said they spread during the reconstruction after the Great Kanto Earthquake [3]. The new role for the former light was to heat pots without smoke, with instant heat control.
3. What "high heat" means on a gas stove and whether it is the biggest flame
If a recipe says "stir-fry on high heat," should you turn the knob to the maximum? Actually, no. According to Tokyo Gas, high heat is when the flame hits the entire bottom of the pot. It is not the maximum setting [4]. Medium heat is when the flame tips just touch the bottom. Low heat is when the flame does not touch the bottom directly. Simmering is the smallest flame [4]. Temperature guides are about 200–230°C (392–446°F) for high, 160–180°C (320–356°F) for medium, around 150°C (302°F) for low, and around 140°C (284°F) for simmering [4]. The difference between high and simmering is about 60–90°C (108–162°F). However, these temperatures vary by model [4]. Users adjust the heat of the pot bottom by watching the flame's position relative to the pot bottom. Unlike volume knobs, maximum is not always correct.
4. Why a gas flame turns red instead of blue
A normal gas flame is blue. It may turn red if ventilation is poor and oxygen is low, or if burner caps are dirty and block air [5]. Burning without enough oxygen is called incomplete combustion, which produces harmful carbon monoxide [5]. Red flames have other causes, so you cannot be certain it is incomplete combustion just by looking. However, if a red flame persists or soot appears, turn off the fire, ventilate, and check the situation [5]. The flame color is a signal that tells you about the condition of the kitchen air. Why flames glow is explained in other articles. Even with normal fire, accidents happen. Stoves have devices for this.
5. How a gas stove helps prevent fires when heating frying oil
Tempura oil can reach its auto-ignition temperature (above 370°C or 698°F) in 5–10 minutes on high heat [6]. Rinnai explains that many home stove fires are thought to be caused by overheated cooking oil [8]. The cooking oil overheating prevention device measures the pot bottom temperature. At about 250°C (482°F), it extinguishes the fire or lowers the flame. This stops it before the 370°C ignition point [6]. Since October 1, 2008, this device has been mandatory on all burners. Before that, some two-burner stoves had it on only one side [7]. The flame-out safety device is also legally required. It detects if the flame goes out due to boiling over or wind and automatically stops the gas. It is a small knob-like part next to the burner [4]. However, you should not leave the stove unattended even with these devices. NITE warns that dirty pot bottoms may prevent accurate temperature measurement, so stay nearby when frying [6]. Also, do not place seasonings behind the stove, as fire can spread to clothes when reaching over it [11].
6. How cassette stoves took over cooking when city gas stops
When city gas stops, gas stoves cannot be used. What took over the kitchen in such times was the cassette stove, which uses canisters. Iwatani's timeline states they released Japan's first tabletop stove without a hose, "Iwatani Hose-Non Cassette Fu," in 1969. In 1976, they adopted a pressure-sensing safety device that stops gas if canister pressure rises [9]. "First in Japan" is based on the company's timeline. The 1978 Miyagi-ken Oki earthquake made them widely known. When city gas stopped in Sendai, the company emergency-shipped 20,000 stoves and 150,000 canisters. This averages 7–8 canisters per stove (150,000 ÷ 20,000 = 7.5) [9]. Shizuoka Prefecture guides suggest keeping one week's supply at home. One canister can boil 1.5 L (about 1.6 quarts) of water 10 times, totaling about 15 L (about 16 quarts) [10]. This is a guideline with conditions; actual use varies. Gas stoves are for varying heat. Cassette stoves are for when gas stops. Both use fire under pots.
7. How to safely observe the flame meeting the bottom of the pot
You can check this with an adult. Ensure sleeves and long hair do not catch fire. Before lighting, find the small knob-like part next to the burner (flame-out safety device). Use a pot with water. An adult changes the flame size while the child watches from a safe distance, comparing the flame and pot bottom position. Observe how the position changes when the flame hits the whole bottom versus just touching it. Heat guides vary by stove and pot [4]. Also, check if seasonings are placed behind the stove [11]. For original sources, the Gas Museum's "From Light to Heat Source" page introduces Meiji-era newspaper ads [1].