FR2607513A1 - Art varnish - Google Patents

Abstract

Manufacture of varnish from a natural resin, preferably dammar resin, or else a wax, or else a mixture of resin and wax. The conversion of this resin, or of this wax, or of this mixture of wax and resin, by means of a process of double decomposition in an aqueous medium, makes it possible to obtain a resinate, or a cirate [lit. = "waxate"], or a ciro-resinate, or a resino-cirate, which has the desirable properties of a varnish. It can be employed mixed with water in the form of emulsion with an aqueous internal phase, which gives it still further very advantageous properties.

Description

 The present invention relates to the manufacture of varnishes.

The varnishes according to the invention are particularly intended for artistic painting and for the restoration of works of art.

 Traditionally, the varnishes used for artistic dyeing and the restoration of paintings are made either from natural resins, such as dammar resin or mastic resin, or from artificial or synthetic resins.

 The only advantage of artificial or synthetic resins lies in their chemical stability. However, in the field of restoring old paintings, the aesthetic qualities of the varnish are a fundamental requirement. However, only varnishes based on natural resins were used by painters, and the aesthetic qualities of varnishes based on artificial or synthetic resins are very significantly different from the aesthetic qualities of varnishes based on natural resins.

 In the range of natural resins used to make table varnishes, dmmar resin is the best, because it combines at least two essential qualities: it is not very acidic, and it hardly turns yellow.

On the other hand it is easily reversible, which is fundamental in restoration. However, it is brittle and brittle, and therefore requires the addition of plasticizers.

 None of the varnishes used to date have all the qualities that one would like for a varnish.

The manufacture of varnish. according to the invention consists in treating a natural resin, preferably dammar resin, or else a wax, or else a mixture of resin and wax. Once treated, the natural resin, the wax, or the mixture of natural resin and wax, have the desirable qualities for a varnish. X
We start from a residue: ie, preferably dammar or from cleaned beeswax, or from a mixture of the resin and wax, in very variable proportions which can go continuously from 070 of wax and IO / ó of resin, at I00 C, o 'of wax and O'> of resin, depending on the use and the desired effect. The wax makes it possible in particular to lower the refractive index of the final varnish. The aesthetic appearance of the varnish therefore depends on the amount of wax added, which can thus be controlled with extreme flexibility.

On the other hand, the wax makes it possible to further improve the chemical and physical properties of the final varnish. The mixture of wax and resin, either the resin alone, or the wax alone, are introduced into a container containing very hot water. A strong base, soda or potash, is gradually added until the resin or wax or the mixture of the two is dissolved
that is, until all of the saponifiable constituents of the resin and the wax are transformed into soaps, which are soluble in water. An excess of base is added: the resin precipitates, and settles, while the impurities are dissolved in the base, which is then discarded.

This operation is repeated: water is added until the mixture is dissolved again, an excess of base is added, then eliminated
This purification operation is repeated as many times as necessary, until a clear solution is obtained.

Then introduced into this solution salts of a metal from group III of the classification.de Mendéléievs such as aluminum. gradually. I1 forms aluminum soaps, and the main constituents of the final product obtained are either an aluminum resinate if one started with resin or an aluminum cirate if one started with wax, or a ciro-resi nate, or an aluminum resino-cirate, or a mixture of the two, if one started with a mixture of resin and wax. After neutralization, purification, settling and filtration, the final product is ready beech used as the basis for a range of varnishes; It can be mixed with water to form an emulsion with an aqueous, stable internal phase. Indeed, metallic soaps make it possible to form emulsions with an aqueous internal phase, stable. From 1 amount of water added (from 0% water for IOyo of resinate, decirate, or ciro-resinate or resino-cirate, up to to I / 2 of water and I / 2 of resinate or cirate or resino-cirate or ciro-resinate), depends the penetration power of the varnish, which can thus be finely controlled, depending on the tables to be treated. On the other hand, the hydrophobic varnish obtained constitutes an excellent ..

- slow protection with respect to the outside environment, in particular humidity.

The varnish is used in dilution in a traditional solvent, such as turpentine.

Example I
Soda is poured into a container filled with 4 liters of very hot water. A mixture consisting of I kilogram of dammar resin and 3oog of purified beeswax is introduced into this boiling medium. The mixture dissolves. Soda is added little by little until the dissolution is complete, that is to say until all the saptifiable constituents of the wax and of the resin are transformed into sodium soaps. An excess of base is added: the mixture settles, and the impurities are dissolved in soda. We throw the liquid away. This operation is repeated as many times as necessary. Then add aluminum salts in the medium in the dry state: aluminum sulphate, until all the soaps are transformed into aluminum soaps. .

 When these precipitate, the liquid is discarded, and the excess aluminum salts are washed off in boiling water. This operation is repeated as many times as necessary, then the acidity of the medium is checked, and the sulfuric acid which neutralizes is formed during the reaction. The product obtained is dissolved in turpentine, then filtered, then used as a varnish, the penetration capacity of which can be adjusted by adding water.

The varnish obtained is
-very optically stable and neutral
-it does not require the addition of plasticizers.

 -It has a very high mechanical strength.

 -it offers excellent resistance to ultraviolet.

 -it is easily reversible.

 -the resin soaps being formed from molecules larger than the resin itself they are therefore thicker, and penetrate less in the pictorial layer, all the less since this varnish can be used in emulsi- to with internal aqueous phase .

 indeed, metal soaps allow the formation of emulsion with an aqueous internal phase, which are stable. The thicker varnish is applied in a more homogeneous layer, with very regularity. On the other hand, in the emulsion state, the varnish thus produced constitutes excellent protection with respect to the external environment and humidity.

Claims (5)

I) Manufacture of varnishes, particularly intended for artistic painting and for the restoration of works of art, characterized in that it consists in treating a natural resin, preferably dammar resin, or else a wax, or else a mixture of natural resin and wax, by a process of double decomposition in an aqueous medium, by introducing this resin, or this wax, or this mixture of wax and resin, in a basic solution, such as a solution of soda or potash in an aqueous medium, bringing the medium to a boil, adding base until all the saponifiable constituents of this resin, of this wax, or of this mixture of wax and of resin are saponified, by adding an excess of base, leaving to settle, eliminating the liquid, and repeating this purification operation until the solution obtained is clear, by reacting on this solution metal salts of group III of the Mendeleev classification, up to '' so that all the soaps are transformed into soaps of this metal of group III of the classification of brendelei <- ev, by adding one. excess of these metal salts, leaving the resinate, or the cirate, or the ciro-resinate, or the resino-cirate, which has formed during the rection to settle, by purifying this resinate, this cirate, this ci ro -resina or this resino-cirate in an aqueous medium, neutralizing the medium, and filtering the product obtained. 2) Manufacturing according to claim I, characterized in that the proportions of the wax and d3 the resins in the mixture of wax and resin, can vary continuously between 0% of wax and IOp of resin, and fOO% of wax and 0% resin. 3) Manufacture according to any one of the preceding claims, characterized in that leresinate, or the cirate, or the ciro-resinate, or the resino-cirate obtained, is used in the form of an emulsion with an aqueous internal phase. 4) Manufacture according to any one of the preceding claims, characterized in that the quantity of water added varies continuously between Q: of water and oOSo of resinate, cirate, resino-cirate with ciro-resinate, and I / 2 of water and 1/2 of resinate, cirate, .resino-cirate or ciro-resinate. 5) Manufacture according to any one of the preceding claims, characterized in that the final product obtained is used in dilution in a traditional solvent, such as turpentine.