Today, this type of processing is often called églomisé and consists in the painting of glass in mixed technique through the deposition of precious metals, such as gold leaf, or sandblasting.
With this technique, in the post-war period, venue’ signs were often produced and, even today, in England, there are historical pub signs, made in this way by expert “gilders”.
The technique of gold leaf on glass is very different from the application of the same on other materials, such as wood. The precious material is presented and sold in small books of wax paper divided into square sheets of about eight by eight centimeters. With a single gram of gold you can get about twenty-five sheets. The beating of the gold is carried out with a mallet that sharpens it until it becomes very thin and impalpable.

The gold leaf can be mirrored on the glass by creating, on the back of the transparent glass, first the outline of the writing or figure on which the precious material will be affixed. Then, on the remaining transparent part of the glass, the gold leaf is placed. With fish glue you create a sticky bottom to make the precious metal stick.
The glue is smeared with a soft brush, once in marten hair, today in synthetic, and with another less thick brush the gold leaf is taken from the book. Once the leaflet is raised, extreme attention must be paid to the movements and movements of air as, in a breath, it could crumble and shatter.
Once placed on the glass it sticks immediately for static effect. Being the fish glue quite liquid allows to adjust the leaf if it is slightly wrinkled. Once the writing or the image is completed, it is left to dry for twelve, twenty-four hours and then you pass with a cotton ball to dry to finish the processing and often you come to create small transparency points.
Then you can retouch with the gold leaf and give then a final protective paint.
The gold that has deposited, seen from the other side of the glass is mirror effect.
You can also avoid this effect by using a glue instead of fish glue.
Different effects can be achieved by discovering and experimenting.

A Spanish designer, around 2018, commissioned me an oval table of about seventy centimeters by one and a half meters, all mirrored gold leaf. It seems easy but it was not at all because, in the large and full surface, any defect stands out. We have done and redone several times the processing in order to obtain a perfect result.
In cases where signs or inscriptions are made, the defects, if present, are much less noticeable because the eye is caught by reading and observing the characters or drawings, whereas in the case of a full surface, inaccuracies are noticed much more.