{"id":1325,"date":"2026-07-04T18:09:40","date_gmt":"2026-07-04T18:09:40","guid":{"rendered":"https:\/\/silicesantacruz.com\/?p=1325"},"modified":"2026-08-24T13:00:09","modified_gmt":"2026-08-24T13:00:09","slug":"sable-de-fonderie-siliceux-caracteristiques-usages-et-achat","status":"publish","type":"post","link":"https:\/\/silicesantacruz.com\/en\/sable-de-fonderie-siliceux-caracteristiques-usages-et-achat\/","title":{"rendered":"Siliceous foundry sand: characteristics, uses and purchasing"},"content":{"rendered":"
\n \n
\n \n
\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n <\/div>\n \n
\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n
\n \n\n
<\/div>\n <\/div>\n <\/div>\n<\/div>\n \n\n
\n Rate this post<\/span>\n <\/div>\n <\/div>\n\n

What is silica foundry sand?<\/h2>\n\n\n\n

Siliceous foundry sand is a moulding sand<\/strong> industrial, consisting mainly of quartz grains (SiO\u2082)<\/a>. To be classified as suitable for foundry use, this product must have a minimum silicon dioxide content of 98 %.<\/p>\n\n\n\n

\"sable<\/figure>\n\n\n\n

This sand is used in the manufacture of moulds capable of containing ferrous and non-ferrous metals at very high temperatures. Of the various types of sand available, silica is the most widely used \u2014 and the most economical \u2014 choice worldwide.<\/p>\n\n\n\n

Composition: silica, binder and water<\/h3>\n\n\n\n

Siliceous foundry sand is made up of three essential components. Each plays a specific role in ensuring the mould\u2019s integrity when faced with molten metal<\/strong>.<\/p>\n\n\n\n

Here is the typical composition of a sand-to-turf mix:<\/p>\n\n\n\n

    \n
  • Silica (SiO\u2082)<\/strong> : 85 to 95 % of the mixture \u2014 it forms the refractory skeleton of the grains of sand and withstands temperatures of up to 1,700 \u00b0C<\/li>\n\n\n\n
  • Bentonite<\/strong> : 5 to 10 % \u2014 this clay binder coats the grains of sand and ensures the mould holds together<\/li>\n\n\n\n
  • Water<\/strong> : 2 to 5 % \u2014 it activates the bentonite and gives the mixture its plasticity<\/li>\n\n\n\n
  • Additives<\/strong> : in small quantities \u2014 mineral black, dextrin or carbon improve refractoriness and surface finish<\/li>\n<\/ul>\n\n\n\n

    The rule to remember is that the mass of water should be about one-third of the mass of clay. Too much water weakens the mould; too little and it loses its cohesion.<\/p>\n\n\n\n

    Different types of foundry sand: green, oil-based and chemical<\/h3>\n\n\n\n

    There are three main types of foundry sand, used according to production requirements. Firstly, the from sand to green<\/strong> \u2014 the most common method \u2014 combines silica, bentonite and water to form a mould without heat treatment. It is suitable for parts measuring between 10 and 800 mm and can be used for production runs ranging from single units to very large batches.<\/p>\n\n\n\n

    Next, oil-based sand (or petrobond) replaces the water with an oil-based binder. Its very fine particle size enables it to reproduce precise details. Please note: the casting process produces smoke and requires adequate ventilation.<\/p>\n\n\n\n

    Finally, the chemical-setting sand<\/strong> a mixture of silica and resins (1 to 2 % of the mixture) activated by a catalyst. This process produces very rigid moulds, capable of accommodating parts weighing up to 80 tonnes. Available ready for use, it is primarily intended for demanding small-batch production.<\/p>\n\n\n\n

    Technical specifications of our foundry sand<\/h2>\n\n\n\n

    Grain size, density and thermal conductivity<\/h3>\n\n\n\n

    The particle size distribution of silica sand is measured using the\u2019AFS fineness index<\/strong> : the higher this index, the finer the grain. For castings, foundries aim for an index of between 55 and 65 AFS. Light alloys such as aluminium can tolerate higher indices.<\/p>\n\n\n\n

    The shape of the grains plays an equally crucial role. Rounded grains reduce binder consumption and improve permeability, whilst angular grains increase the mechanical strength of the mould.<\/p>\n\n\n\n

    Here are the three key physical properties to remember:<\/p>\n\n\n\n

      \n
    • Bulk density<\/strong> : approximately 1.52 kg\/dm\u00b3 for dry silica sand<\/li>\n\n\n\n
    • Thermal conductivity<\/strong> : 0.25 W\/(m\u00b7K) \u2014 sand conducts heat slowly, which slows down the cooling of the cast metal<\/li>\n\n\n\n
    • Specific heat capacity<\/strong> : 830 J\/(kg\u00b7K), a parameter that directly influences the solidification rate of the components<\/li>\n<\/ul>\n\n\n\n

      Heat resistance and permeability<\/h3>\n\n\n\n

      Pure silica reaches a vitrification temperature of 1,700 \u00b0C<\/strong> \u2014 a threshold that explains why this material dominates the global foundry industry. In practical terms, sand does not melt on contact with steel or molten cast iron, the casting temperatures of which rarely exceed 1,600 \u00b0C.<\/p>\n\n\n\n

      \n
      \"\"<\/figure>\n\n\n\n
      \"\"<\/figure>\n\n\n\n
      \"sable<\/figure>\n<\/figure>\n\n\n\n

      Permeability, for its part, directly determines the quality of the parts produced. During casting, gases form within the mould cavity. If they do not escape in time, they cause internal defects known as gas porosity \u2014 cavities that weaken the final component.<\/p>\n\n\n\n

      Firstly, a coarse grain promotes the release of gases, and thus permeability. Secondly, a fine grain improves the surface finish, but reduces that very same permeability. This is why the choice of grain size is always the result of a a trade-off between surface finish and mould ventilation<\/strong> :<\/p>\n\n\n\n

        \n
      • High AFS index<\/strong> : better surface finish, increased risk of premature vitrification and porosity<\/li>\n\n\n\n
      • Low AFS index<\/strong> : maximum permeability, rougher workpiece surface<\/li>\n<\/ul>\n\n\n\n

        Which metals can be cast using this sand?<\/h2>\n\n\n\n

        Aluminium, bronze and brass<\/h3>\n\n\n\n

        Require fine sand (70 to 90 AFS<\/strong>) to achieve a smooth finish and minimise the need for touch-ups.<\/p>\n\n\n\n

        Cast iron, steel and ferrous alloys<\/h3>\n\n\n\n

        Require pure silica with a purity of over 98 % to withstand extreme temperatures (up to 1,550 \u00b0C). A coarser grain size is used (55 to 65 AFS<\/strong>) with a little charcoal to prevent the metal from sticking to the mould.<\/p>\n\n\n\n

        How much does foundry sand cost?<\/h2>\n\n\n\n

        The price depends on the purity and preparation of the sand:<\/p>\n\n\n\n

          \n
        • In bulk (Industry):<\/strong> From \u20ac60 to \u20ac150 per tonne<\/strong> for raw silica. Allow for \u20ac2 to \u20ac5 per kg<\/strong> for ready-to-use technical sand.<\/li>\n\n\n\n
        • Small-scale operations (Artisans \/ Workshops):<\/strong>\n
            \n
          • 1 kg:<\/strong> \u20ac8 to \u20ac12 (ideal for jewellery or test items).<\/li>\n\n\n\n
          • 5 kg:<\/strong> \u20ac20 to \u20ac30 (matte frame size).<\/li>\n\n\n\n
          • 25 kg:<\/strong> \u20ac45 to \u20ac60 (the standard economy fare).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n