Flux

Flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining.

Description of what it is like

Flux can appear as a powder, paste, or liquid, depending on its specific type and application. Common fluxes include silica sand, borax, limestone, and rosin.

Origin and where to find it

• Sand (Silica): Found in riverbeds, beaches, and deserts.
• Limestone: Sedimentary rock found in mountains and cliffs.
• Borax: Found in dry lake beds (evaporite deposits).
• Rosin: Derived from pine tree resin.
• Ash: Wood ash can sometimes act as a flux due to potash content.

Minimum processing required

• Grinding: Most solid fluxes like limestone and sand need to be ground into a fine powder.
• Purification: Some natural sources may need washing or refining to remove impurities that could contaminate the metal.
• Mixing: Sometimes mixed with water or oil to form a paste.

Tools needed to work on it

• Mortar and Pestle: For grinding solid minerals.
• Containers: For storing the powder or paste.
• Sieve: To ensure uniform particle size.

Common forms of use

• Powder: Sprinkled onto hot metal during forge welding.
• Paste: Applied to joints before soldering.
• Additive: Mixed with ore in a furnace during smelting.

Possible substitutes

• Sand: Can substitute for borax in forge welding iron, though higher temperatures are needed.
• Ash: Wood ash or straw ash can work in some clay or glass processes.
• Glass: Ground glass can act as a flux.
• Animal Fat: Can be used in soldering lead (primitive).

Limitations and common failures

• Incorrect Type: Using the wrong flux for the metal (e.g., using rosin for iron welding) will result in failure.
• Contamination: Dirty flux can introduce impurities.
• Moisture: Damp flux can cause steam explosions or porosity in the weld.

Risks and safety

• Fumes: Fluxes often release toxic fumes when heated (e.g., fluoride fumes). Ventilation is critical.
• Corrosivity: Some fluxes are acidic and can corrode the metal if not cleaned off after use.
• Burns: Flux becomes molten and sticky at high temperatures.

Related materials

• Sand: A common high-temperature flux.
• Limestone: Used as flux in iron smelting.
• Pine Resin Glue: Rosin source.
• Boron: Key element in borax.