CRYSTALLIZATION OF POTASSIUM ALUM ONTO VARIOUS MATERIALS Field of the invention

The present invention concerns the crystallization of potassium alum onto different materials or substrates with the aim of producing ornamental articles, decorations or fabrics.

State of the art

Potassium alum, whose chemical formula is the following: KAI(SO ₄ ) ₂ , and is present in nature in various hydration forms, is a salt widely used in a variety of industrial applications. In dyeworks, for example, it is used as a mordant, while in the food industry it is used as an antioxidant to prevent bananas from going bad during storage, in medicine as a hemostatic agent and finally in the cosmetics industry for the preparation of astringent toners, preparation of deodorants, footbaths etc. Alum crystals, however, have the drawback that they deteriorate, due essentially to the tendency of said crystals to lose their water molecules and to crumble. Description of the invention

The Applicant has now unexpectedly found that ornamental articles, decorations or fabrics can be prepared by crystallizing potassium alum onto materials or supports of different materials such as: plastic, resin, wood, various types of crystals, and also desiccated terrestrial and marine plants, coral, rocks, granites and stone in general, metals, ceramics, paper, cardboard.

Therefore, the invention provides in particular a process for preparing an ornamental article, decoration or fabric comprising a support or material essentially consisting of the aforesaid materials onto which potassium alum crystals are deposited. Said process comprises in particular the following steps: a) preparing an aqueous potassium alum solution which optionally contains the support, obtained by partially or totally dissolving the anhydrous or crystalline form of the corresponding salt, b) adding the support if not already present in step (a); this is followed by crystallization, leaving the solution to stand for a period of time sufficient to allow crystals of the desired size to precipitate and deposit onto the support;

c) removing the ornamental article, decoration or fabric from the aqueous solution, then drying.

The concentration of the aqueous solution obtained in step (a) is generally between 1 and 500 g/litre. In step (a) an unsaturated or supersaturated solution of potassium alum can in fact be prepared.

The dissolution temperature in step (a) is a function of the solution concentration. The more concentrated the solution with potassium alum, the greater the relative dissolution temperature which is generally between 20 and 150°C. The cooling time of the solution is a further parameter able to modulate crystal size.

Generally this is between 1 hour and 40 days.

The process of the present invention provides a further step (d) which consists of applying a coating consisting of a transparent or opaque varnish, or a plastic or glazing varnish, or similar products able to impart greater brightness and/or rigidity to the crystal.

This coating is applied for the purpose of protecting the crystal from the external environment, which could otherwise alter the relative degree of hydration and promote the crumbling thereof.

Said coating can be applied either by spraying or by immersing the article, decoration or fabric in suitable baths.

The preferred technique employed is spraying.

The process of the invention can include a step for colouring the crystal which can be carried out in accordance with either of the two following alternative techniques:

A) the aqueous solution prepared in step (a) already contains a water soluble pigment or colour, and colouring takes place in the crystal formation phase in step

(b),

B) colouring is carried out in a step (c') after drying of the product, by applying colouring paints which form a protective layer that protects them from the external environment in addition to colouring the crystals. A further aspect of the present invention is a process for preparing an ornamental article, decoration or fabric onto which crystals of different sizes and/or colours are

fixed.

Said process is characterized by comprising steps (a)-(c) and optionally (d) of the process of the present invention, with possible colouring in accordance with technique (A) or (B), and additionally by comprising the following steps: a1 ) immersing the article obtained by the preceding process in an aqueous solution obtained by partially or totally dissolving anhydrous potassium alum or the crystalline form at a temperature insufficient to completely dissolve the crystals obtained by the preceding process, b1 ) leaving the solution to stand in order to promote precipitation of crystals onto the support and optionally onto the crystals already previously formed, c1 ) removing the fabric, ornamental article or decoration from the aqueous solution, then drying.

Again in this case, as in the previous process, a step (d1 ) is preferably encompassed consisting of applying a protective coating onto all the crystals by spray application of an opaque, transparent, plastic or glazing protective varnish.

EXAMPLE 1 - Preparation of a dwarf tree (Bonsai) with small branches on which the crystals are deposited

3 kg of potassium alum are dissolved in 20 litres of water. The water is heated until partial or complete dissolution of the potassium alum. The bonsai is added to the solution which is left to cool to ambient temperature.

After 15 to 20 hours, deposition and fixing of crystals onto the whole plant is achieved.

On completion, the article is sprayed with transparent varnish and left to dry at ambient temperature.