Drawing soap is a metallic-soap based dry lubricant that forms a lubricating film between die and metal in wire and profile drawing. It is not a cleaning soap that dissolves in water; it is a consumable that keys into the phosphate layer and forms a film under pressure and heat.
Drawing soap is a dry drawing lubricant that reduces the friction of metal passing through a die in wire, tube and profile drawing and in cold forming. The word “soap” in the name can mislead: this is not a cleaning soap that lathers in your hand and dissolves in water. Chemically it is a metallic-soap based lubricant, and its job is not to wash but to form a continuous lubricating film between the die and the metal surface.
If that film is thick enough, continuous enough and durable enough under the pressure and temperature inside the die, the metal never touches the die directly and friction and wear are minimised. The moment the film tears, die wear, surface scoring, pick-up and wire breaks begin. This makes drawing soap one of the cheapest-looking consumables on the line and, at the same time, one of the most direct determinants of die life and surface quality.
This article covers what drawing soap is, what it corresponds to chemically, how it lubricates in dry drawing, what types exist, and why it works on top of a phosphate layer rather than on its own. Kimfosan's drawing soap range, Kimkal, is the reference for the behaviour described here.
Drawing a wire down to a smaller diameter means forcing the metal through the tapered entry of a die. During that passage, very high contact pressure builds between the wire surface and the die, along with heat generated by friction. Without lubrication the two surfaces weld to one another: metal sticks to the die (pick-up), the wire surface scores and the die wears rapidly. The function of drawing soap is to prevent that contact.
In practical terms drawing soap protects four things at once:
Our wider treatment of how lubrication affects friction and heat, friction in cold forming, explains in physical terms what the soap is really doing on the line.
Drawing soaps are powder or granular lubricants based fundamentally on metallic soaps. The term “metallic soap” means the salt formed by a fatty acid (stearic, oleic and so on) with a metal such as sodium or calcium; sodium stearate and calcium stearate are the most common base components. Fillers, slip additives and flow modifiers are added to the formulation to tune lubricating performance and flow behaviour.
What these components have in common is that they stay solid (as a powder) at room temperature but soften under pressure and heat to give a plastic, adherent film. In other words, drawing soap is a material engineered to turn into a lubricant precisely under the conditions of the drawing zone. The type of base soap (sodium or calcium) and its softening point are the main variables that determine which line speed and which operation a given soap suits.
Lubrication in wire drawing can be done two ways. In wet drawing the wire runs in a liquid lubricant. In dry drawing the wire passes through a soap box immediately before the die and picks up powder or granular drawing soap on its surface. Kimfosan's Kimkal range is for dry drawing, and the mechanism described here is the dry drawing mechanism.
The critical point is this: the loose powder that sticks to the wire in the soap box is not yet a lubricant. When the wire reaches the converging entry cone of the die, that powder is compressed under pressure, softens with frictional heat and becomes a continuous film adhering to the surface. In other words the lubricating film forms at the die entry, not in the soap box. We cover how that film is established, why it breaks at high speed and what soap box discipline looks like in dry drawing soap film stability.
Soaps used in dry drawing fall into two families according to the relationship they form with the phosphate layer:
| Property | Reactive soap | Neutral soap |
|---|---|---|
| Base soap | Predominantly sodium | Predominantly calcium |
| Relationship with phosphate | Reacts, forms zinc soap | Does not react, leaves a physical film |
| Film strength | More stable at high pressure/temperature | Depends on thickness and particle structure |
| Cleanability | Harder (surface-bonded residue) | Easier (removed by alkaline washing) |
| Typical use | Heavy drawing, multi-die lines | Light passes, fine wire, clean surface afterwards |
Which family suits which line is decided by drawing speed, reduction per die, wire diameter and the operation the wire will see after drawing (welding, heat treatment, coating). We set that choice out with a checklist in drawing soap selection.
Drawing soap on its own, on a bare steel surface, will not deliver the expected performance. A bare surface has no reservoir to hold the soap; under the pressure inside the die the film thins and tears. This is exactly why the surface is phosphated before drawing.
Zinc phosphate coating creates a porous, crystalline carrier layer on the metal surface. With its sponge-like structure this layer holds the soap and, under pressure inside the die, feeds it back to the surface from those pores so that film continuity is maintained. The phosphate layer and the soap do not work independently but as a pair: the layer is the surface that carries the soap, the soap is the film that makes it slippery. How a conversion coating forms, and why it is porous, is explained in what is phosphating.
The phosphate layer is the surface the soap holds onto; the drawing soap is the film that makes that surface slippery. Choosing one independently of the other is the most common source of drawing problems.
The practical consequence of this dependency: before changing the soap in response to die life or surface complaints, verify that the phosphate coating weight and the bath balance are right. A good soap will not rescue a poor carrier layer.
Drawing soaps are generally supplied as powder or granules. The physical form affects how the soap flows in the box, how evenly it transfers to the wire surface and how it builds film. Fine-particle powder formulations run more smoothly and cleanly on fine wire, while coarser formulations with higher film-carrying capacity are preferred on heavy, multi-die lines with larger diameters.
Regardless of physical form, all drawing soaps are hygroscopic — they draw moisture from the air. Soap that has taken up moisture cakes, loses its flow and transfers unevenly to the wire, breaking film continuity. Performance is therefore largely determined by storage conditions before the pack is even opened: sealed packaging, a dry and cool environment, and storage away from heat and steam sources.
There is no single “best drawing soap”; the right soap depends on the conditions of the line. The main inputs that govern the choice are:
Once these headings are clear, the reactive-or-neutral choice and the right formulation follow almost by themselves on most lines. Why soap consumption is not on its own a quality indicator, and the right way to reduce it, is covered in reducing drawing soap consumption.
Drawing soap is a metallic-soap based consumable that forms a lubricating film between die and metal in dry drawing. It shares only a chemical family name with cleaning soap; its function and design are entirely different. It comes in two main families, reactive and neutral, and the right choice depends on line speed, reduction, wire diameter and the post-drawing operation. Most importantly, drawing soap does not work alone: it works as a pair with the phosphate layer that holds it. How that pair is set up where there is contact on the inside surface too, as in tube drawing, is covered in tube drawing lubrication.
If you would like to assess the right soap character and coating weight together for your substrate, reduction schedule and line speed, talk to our technical team. For technical documents and product data sheets, see our document centre. Producing phosphating chemicals and drawing soaps since 1982 and Türkiye's leading drawing soap manufacturer, Kimfosan provides process support tailored to field conditions from its plant in Kartepe / Kocaeli.
Drawing soap is a metallic-soap based dry drawing lubricant that forms a lubricating film between the die and the metal surface in wire, tube and profile drawing and in cold forming. It is applied as a powder or granule. It is not a water-soluble cleaning soap; it softens under pressure and heat to give a film that adheres to the surface.
It prevents the metal from contacting the die directly during drawing. That slows die wear, protects the wire surface from scratches and scuffing, keeps frictional heat under control so breaks are reduced, and lowers the force required for drawing. In short, it directly determines die life and surface quality.
Reactive soap is predominantly sodium based and reacts with the zinc in the phosphate layer to form a chemically bonded zinc soap film on the surface; it is more durable in heavy drawing. Neutral soap is predominantly calcium based, does not react and leaves a physical film; it is easier to clean off after drawing. The right choice depends on line speed, reduction and the post-drawing operation.
Zinc phosphate coating acts as a carrier layer that holds the soap in its porous, crystalline structure. Without that layer the soap cannot be carried into the die and will not stay in place under pressure; the film thins in the first die and leads to metal-to-metal contact. This is why soap works on top of a correctly prepared phosphated surface.
Both are used; the choice depends on wire diameter and line conditions. Fine-particle powder formulations run more smoothly and cleanly on fine wire; coarser formulations with high film-carrying capacity are preferred on heavy, multi-die lines with larger diameters. Both forms take up moisture, so both must be stored dry and sealed.
Reactive soap reacts with the phosphate layer to form zinc soap; neutral soap leaves a physical film. Which suits which line is decided by drawing speed, reduction ratio, wire diameter and what the wire has to go through after drawing.
Read →In dry drawing the lubricating film forms when powder picked up from the soap box is pressed onto the surface at the die entry by pressure and heat. We look at why that film breaks at high speed, the symptoms it shows, and the discipline required on the soap box side.
Read →A zinc phosphate coating is a porous crystalline layer that grows on the steel surface through an acidic bath reaction. This guide explains how the layer forms, what coating weight actually means, and why the layer is indispensable in cold forming.
Read →