29/10/2025
The following is an extract from a research paper we have been compiling. Our research is ongoing, and the paper is updated regularly as new information and products become available. I have posted many times about safety when using your forge, silicates are a real hazard and it is forecast that we will see an increase in silicate-based cancers over coming years. Silicate based stone has been banned in the building industry due to the high incidents of stoneworkers developing silicosis. Please be aware of and consider the risks.
Thermal Expansion Characteristics of Commons Forge Linings:
Ceramic Wool
• Highly flexible and compressible.
• Designed to absorb thermal movement.
• Exhibits significant expansion/contraction during thermal cycling without structural failure.
Cement-Based Castables
• Rigid and brittle once cured.
• Thermal expansion: ~0.6–0.7% up to ~1250 °C, then slight shrinkage due to sintering.
• Low tensile strength; cracks under uneven stress.
Zircon Based Refractory
• Applied as a refractory coating over fiber.
• Formulated to resist thermal shock and spalling.
• Maintains surface integrity under cycling; does not exhibit large dimensional changes like wool.
• Acts as a protective barrier rather than a structural layer.
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Interaction Between Layers
• When castable is applied directly over ceramic wool, differential movement causes cracking and debonding.
• Zircon, when applied over castables or fiber, is designed to:
o Bond well to the substrate.
o Reduce slag adhesion and surface erosion.
o Minimize cracking by matching thermal expansion of underlying refractory.
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SUMMARY:
Cement based castable refractory contains between 35% to 55% silicates. Kaowool contains between 45 to 55% silicates by weight.
Silicates are known carcinogens.
When used as a forge lining Cement based castables form a rigid coating over the ceramic wool (Kaowool), whilst resistant to thermal shock the rigid and brittle nature of cement based castables makes this product less than ideal given the expansion and contraction of the underlying Kaowool during high temperature use.
As the castable degrades due to cracking silicates are expelled into your work environment in the form of dust. This dust is inhaled both during the time you are forging and as the dust is disturbed at any time you are in that environment.
Zircon based refractory may contain very minor amounts of silicates. (may be present in some less pure forms) Zircon based refractory is designed to match the substrate (Kaowool) expansion and contraction. This coating will degrade over time however particle expulsion is inert or may contain very minor amounts of silicates. (depending on the purity of the product used)
Whilst the hard refractory applied over the Kaowool traps the silicates cement-based lining can be a health hazard. Our research shows that zircon-based linings are much lower risk.
WARNING:
This paper is prepared as a guide; significant research has been undertaken utilising hundreds of published data sources. It is recommended that you conduct your own research when considering which refractory materials you will incorporate in your forge.
Moosehead Forges uses high purity zircon-based refractory. This is based on many years of research and experience. We do not consider the risk of harmful particle expulsion as zero and recommend forge owners take care when using their forge and consider the risks.
