Hold 40-80 L of water in a stone, metal or lined tub within arm’s reach of the anvil: one 0.5 kg piece quenched from 800 C warms 40 L by only about 1 K, but if that heat boiled water it would make up to about 140 L of steam at the surface and scald the face. Plunge the piece away from the body, change the water when it is too hot to quench quickly, and keep a separate barrel of at least 200 L for fire.
Part of Workshop & Forge Design
A quench tank is the tub of water in which hot steel is cooled rapidly to harden it or to make it safe to handle, placed in the smithy’s line between anvil and finishing area.
The Tank’s Size Is Set By Steam And Splash, Not By Heat
The workshop guide specifies a stone, metal or lined wooden tub of 40-80 L within arm’s reach of the anvil, with the water changed when it becomes too hot, because warm water quenches too slowly. The forge setup guide is less demanding: a container of at least 20 L (Forge Setup). The larger figure is the safer one. The heat a quench puts into the tank is small, as the arithmetic shows; the hazard is the steam at the surface of the hot metal.
Worked Example: Heat, Warming And Steam
Inputs (specific heats and the latent heat of water are standard physical values recalled, not read from this corpus): steel 0.49 kJ per kg per K; water 4.18 kJ per kg per K; latent heat of boiling 2,257 kJ per kg; steam at 100 C occupies about 1.67 m³ per kg. A piece of 0.5 kg is quenched from 800 C to 20 C, a fall of 780 K. A litre of water is taken as 1 kg.
- Heat released = 0.5 × 0.49 × 780 = 191 kJ.
- Warming a 40 L tub: 191 ÷ (40 × 4.18) = 1.1 K. An 80 L tub: 191 ÷ (80 × 4.18) = 0.57 K.
- Twenty such quenches in a 60 L tub: 20 × 191 = 3,820 kJ ÷ (60 × 4.18) = 15 K, so the water rises from 20 C to about 35 C. This ignores heat lost to the air, so it is an upper estimate.
- A hundred quenches: 100 × 191 = 19,100 kJ ÷ 251 kJ/K = 76 K, so the 60 L would approach 96 C without losses. That is why the guide says to change the water.
- Steam: if all 191 kJ went into boiling, the water boiled would be 191 ÷ 2,257 = 0.085 kg, and 0.085 × 1.67 = 0.14 m³, about 140 L of steam. Most of the heat warms the tub rather than boils it, so this is an upper bound, but the steam forms in the first seconds at the surface of the hot piece, which is where the smith’s hand and face are.
What You Need
- A tub of stone, metal or lined wood holding 40-80 L. A wooden tub left empty shrinks and leaks, and hot steel dropped on its bottom chars it.
- A lid or cover against debris, children and the cold
- A separate barrel of at least 200 L for fire fighting, not the quench tub
- Tongs long enough to hold the piece at arm’s length
- A bucket and a short, clear route to the water point for changing the quench water
Method: Quench Without A Scald
Step 1: Place the tub within arm’s reach of the anvil, on the side away from the forge, on a floor that drains. Water spilled on a hot earth floor makes mud and steam.
Step 2: Hold the piece at the end of the tongs, lower it into the water edge-first and away from the body, and move it through the water to break up the steam film that forms around it.
Step 3: Check the water temperature before each session. The workshop guide’s test is practical: if it quenches slowly, it is too warm.
Step 4: Change the water when hot, using a bucket, not by carrying the whole tub.
Step 5: Never quench in a closed container or with a lid on. Steam needs a way out.
Common Mistakes
- Leaning over the tub. Steam rises straight into the face.
- Quenching a hollow or socketed piece. Water trapped inside flashes to steam and spits.
- Using the quench tub as the fire reserve. It is warm, full of scale and rust, and too small for the 200 L the workshop guide asks for.
- Using oil without preparation. Oil is a different quench with a different hazard (see Safety).
Safety
Steam burns and oil fires
A plunge of hot steel into water throws steam and hot droplets upward; keep the face and forearms back and wear a leather apron. If a burn occurs, cool the area at once with running cool water (Burns Treatment). Quenching oil is a fire risk: steel at 800 C is far above the temperature at which vegetable oils smoke and ignite. Use a small, deep, covered metal container, keep a lid and dry sand beside it, and keep it well away from the fire and sparks. Never use water on an oil fire (Fire Safety & Suppression).
What’s Next
- Learn next: Coal & Charcoal Storage — the fuel side of the line
- Combine with: Metal Tempering — what the quench is for