Abstract: Articles formed of lead glass or crystal are treated in order to minimize the tendency for the article to leach lead or other heavy metals into products, such as alcohols or acidic foods, placed in contact therewith. In a preferred embodiment, flasks formed of glass containing between about 12% and 40% by weight lead oxide are provided with a thin layer or slip of kaolin, and heated at a temperature and for a time sufficient to exchange lead ions in the flask with ions other than lead in the kaolin layer. Preferably, the layer is applied as a thixotropic barbotin (slip) of pure hydrated aluminum silicate, and coated flasks are exposed to a temperature of between about 300.degree. C. and the strain point of the glass forming the flask and for a time ranging between about 3 and about 6 hours; rapid heating and cooling is avoided.

Abstract: An article made by treating the surface of a solid article made of a material having a vitreous structure, such as crystal, lead glass and the same, and containing some amounts of heavy metals such as lead, said surface being liable to be into contact with products of acid character, such as alcohols e.g. cognac, whisky, wines or fruit juices, or acid foodstuffs, with a view to prevent said heavy metals from drifting into said acid products, characterized in that it comprises forming in a superficial area of said surface, after partially removing the lead ions from said area, a silico-aluminous diffusion barrier opposing said drift into said acid product, by ion exchange between said material having a vitreous structure and a coating temporarily laid upon said surface, said coating comprising a silico-aluminous crust resulting from the heating of a kaolin layer laid upon said surface under the form of a thixotropic slip of pure hydrated aluminum silicate.

Abstract: Container made of crystal for containing any product and drink with acid characteristics, characterized in that in order to prevent the lead from migrating from the crystal to the products and drinks, the container has on its internal surface a thin and continuous film made of unleaded glass forming a "screen".

Abstract: Container made of crystal for containing any product and drink with acid characteristics, characterized in that in order to prevent the lead from migrating from the crystal to the said products and drinks, the said container has on its internal surface a thin and continuous film made of unleaded glass forming a "screen".