The present invention relates to compositions comprising the reaction product of amorphous silica or ultra-fine silica and one or more bases. The present invention also relates to materials and method involving the use of such products. In particular, the present invention i.a. relates to new mineral wool products, e.g. products comprising man-made vitreous fibres (such as glass fibres, slag fibres, stone fibres and rock fibres) or perlite, having included therein a binder component which comprises amorphous silica and aklali metal organosiliconates, e.g. potassium methyl siliconate. An important feature of such products is the preparation of the binder systems under vigorous mixing. Such products provide good fire, heat and sound insulating properties. The present invention also provides to a method for removing odorous substances from a gas where materials prepared from ultra-fine silica, water, and one or more components enabling porosity-conferring binding of the material, e.g. a base or bases. Furthermore, the invention provides methods for thixotroping bitumen.