Process for the Selective Etching of a Glass Article Surface

1 . Process for the selective etching of at least one glass article surface with aqueous solutions of hydrofluoric acid comprising the following steps, in sequence:

a) a protective step during which at least one area of the surface that should not be etched is protected by deposition of a protective coating, so as to obtain a selectively coated glass article surface,

b) an attack step during which the uncoated areas of the surface are etched by contacting the selectively coated glass article surface with the acid solution,

c) a cleaning step consisting of cleaning the glass article surface by wiping the protective coating followed by a rinsing of the surface,

characterised in that the protective coating is a coating layer of low-temperature melting wax that is deposited on selective areas of the glass article surface during the protective step by means of at least one dispensing device that comprises at least one ink-jet head, which fuses the wax.

2 . Process according to claim 1 , characterised in that the glass article surface is of at least 5 m 2 .

3 . Process according to claim 1 , characterised in that the protective step comprises for a given point of the surface to be protected at least one excursion of the ink-jet head dispensing a ribbon of molten wax.

4 . Process according to claim 1 , characterised in that the protective step comprises three successive excursions of the dispensing ink-jet head for a given point of the surface to be protected.

5 . Process according to claim 4 , characterised in that the ink-jet head is positioned slightly differently at each excursion so as to fill possible gaps between previously deposited wax ribbons.

6 . Process according claim 1 , characterised in that the wax melting point is from 50 to 140 degrees Celsius.

7 . Process according to claim 1 , characterised in that the wax melting point is from 60 to 95 degrees Celsius.

8 . Process according to claim 1 , characterised in that the wax is selected from any mixture in whatever proportions of at least one natural and/or synthetic particular wax.

9 . Process according to claim 8 , characterised in that the molten wax has a dynamic viscosity at 100° C. of from 5 to 30 mPa·s and, preferably of from 10 to 20 mPa·s.

10 . Process according to claim 8 , characterised in that natural wax is selected from mineral waxes extracted from oil, like paraffin and microcrystalline waxes.

11 . Process according to claim 8 , characterised in that synthetic wax is selected from ethylenic polymers like polyethylene and polyol ether-esters.

12 . Process according to claim 1 , characterised in that the attack step has duration, which is no shorter than 5 minutes.

13 . Process according to claim 1 , characterised in that during the cleaning step, the wiping is performed by leeching the glass article surface with hot water.

14 . Process according to claim 13 , characterised in that a detergent is present in the wiping water.

15 . Glass etched by a process according to claim 1 .