The white powder you see sprinkled on hot steel during forging is flux , most commonly based on borax.

What that white powder actually is

In most modern blacksmithing and forge‑welding videos, the white powder is a borax‑based forge flux.

It’s usually a fine mix of:

  • Borax (sodium borate) as the main ingredient.
  • Silica or sand to help form a glassy slag.
  • Sometimes sodium carbonate and iron oxide or other additives depending on the smith’s recipe.

A few sources also mention “white ash” being used in some contexts, but for the classic “sprinkled on hot metal before welding” shots, people are almost always talking about borax‑based flux.

What flux actually does in forging

When steel is heated for forge welding, it quickly forms scale (iron oxide) on the surface, which can ruin a weld.

Flux solves several problems at once:

  • Prevents oxidation (scale): Flux forms a liquid/glassy layer that keeps oxygen away from the hot steel surface.
  • Dissolves impurities: It chemically reacts with existing oxides and dirt, turning them into slag that can be squeezed out under the hammer.
  • Improves metal “flow”: By cleaning and lubricating the joint, it helps the two steel faces weld together more easily when struck.

Think of it like a cleaning and protective glaze that lets the hot metal fuse cleanly instead of burning and crumbling.

Common recipes and variations (as seen online)

You’ll see different “home shop” recipes discussed in forums and blog posts:

  1. Balanced mix (simple DIY)
 * 1 part borax
 * 1 part silica
 * 1 part sodium carbonate
  1. Borax‑heavy mix
 * 2 parts borax
 * 1 part sand
 * 1 part sodium carbonate
  1. Straight borax from the box
    • Many hobby smiths just use plain borax laundry booster, sometimes with a small tweak (like a bit of sugar or iron filings) for tougher welds.

All of these are trying to do the same basic job: create a fluid glassy layer that eats scale and protects the weld surface.

Mini “forum discussion” view

“You will only see it in forge welding videos; it is flux… The purpose of flux is to avoid scale from forming on the metal that is being welded together.”

“It is borax, used as forge welding flux… cleanliness is very important so flux is often used to prevent scale formation.”

These kinds of Q&A threads pop up a lot in blacksmithing communities, because shorts and viral clips often show the powder but never explain it.

Is this a trending / “latest” topic?

Recently, there’s been a bit of a shift in online smithing content:

  • More YouTube shorts and TikToks showing dramatic welding shots with the white powder.
  • Blog posts in 2024–2025 specifically titled “what is the white powder used in forging” because people keep searching that phrase after watching short clips.
  • Some newer articles also mention sustainability angles like recycling flux and optimizing formulations in industrial forging.

So while the material itself is old‑school, the question “what is the white powder used in forging” has become a bit of a micro‑trend as more people binge blacksmithing shorts.

Quick FAQ

Is it always borax?
Usually yes in hobby and demo forging, but some shops use custom flux blends or different salts depending on the steel and process.

Is it dangerous?
Like most powders, you don’t want to breathe it or get it in your eyes. Use ventilation, a mask if you’re sprinkling a lot, and basic shop PPE. Do you always need flux?
Not for every forge operation; you only see it during forge welding or other high‑heat joints where a clean bond is needed.

TL;DR

The white powder used in forging is a borax‑based forge flux that prevents oxidation, dissolves scale, and helps hot steel weld together cleanly.

Information gathered from public forums or data available on the internet and portrayed here.