Ever wondered how they get pub mirrors to look like that? What manner of gilding gets you there? What is acid-etched gilding? Can you go about it at home, or do you need professional equipment and assistance?
All this and more today as we explore the method and history of acid-etched gilding!
Table of Contents
- Acid-Etched Metal in Renaissance Europe
- Acid-Etched Glass
- Acid-Etched Water Gilding
- Final Words
- FAQs Acid-Etched Gilding
Acids can dissolve metals by chemical reaction, a process that can be used to etch designs into metal surfaces instead of the more time-consuming and technically demanding method of engraving by hand.
The French scholar Jehan le Begue, for example, wrote a recipe for acid-etching on iron in 1531. The idea was to distill ammonium chloride, ordinary alum, and ferrous sulfate in a mixture of water and vinegar. Craftsmen, however, rarely recorded their methods and many developed their own techniques, despite basic principles remaining unchanged.
The entire metal surface to be etched is first cleaned thoroughly and then coated with an acid-resistant substance such as beeswax. This is called a ‘resist’. The design is then engraved in the wax to expose the metal underneath.
The prepared metal is thus immersed in a solution of hydrochloric or nitric acid and water until its exposed areas have been eaten away to the desired depth. The resist is then removed to reveal the etching. Afterward, gilding or blackening can be added to accentuate the design.
Acid-Etched Metal in Renaissance Europe
The word Etching is from an ancient Germanic word for ‘eat’, using corrosive acids to bite designs into hard surfaces. The background can either be eaten away so the design stands out in relief, or the design itself can be bitten into the surface, or vice versa.
Etching has been applied to a broad range of luxury goods, especially durable items made of steel such as weapons, locks, and tools. The technique creates a shallow relief making it possible to create highly decorated objects without compromising the structural integrity of the metal.
Between 1500 and 1750 production of this commodity centered in southern Germany and northern Italy where etched armor of this kind was a specialty.
Daniel Hopfer of Augsburg was a renowned etcher of armor and is widely thought to have invented etched metal plates for printing on paper. His designs were well-known during his lifetime and served as models for craftspeople working in a range of media, both in warfare and elsewhere.
Decorative glass of the nineteenth and twentieth centuries sometimes used etching to produce a frosted pattern, the two common methods by which this is achieved being sand-blasting and acid-etching.
Acid etching was usually done in two stages in these instances: firstly the whole glass would be etched to a matt finish; then a different type of acid-etch would be utilized to bring back some areas to a clear finish.
Sand-blasting, on the other hand, is done by pressure-spraying a fine abrasive onto the glass. Usually, the pattern in the glass is made by masking off the clear areas with a protective film. Acid etching is sadly rarely done these days for safety reasons but it does have a softer, more pleasing appearance than sand-blasting.
Acid-Etched Water Gilding
The craft of water gilding is ancient and has been used in many cultures. Often, this process is in more contemporary gilding used to apply gold and silver leaf to the reverse of the glass or to apply gold to the hive cell etched glass and the weave border of a piece. In any instance, each piece of glass should be thoroughly cleaned and dried with a lint-free cloth.
- The glass is then coated by brushing it down with water size (adhesive). The glass has to be very wet to attract and adhere to the metal leaf. The gold on the hive cells is 22 crt gold leaf. It is supplied in loose-leaf booklets.
- Removing a single leaf onto a gilding pad and cutting slices using a knife, use a squirrel tip brush (charged with static electricity from rubbing the brush against my hair) whose static attracts the gold leaf onto the squirrel tip.
- The gold is then placed in front of the area to be gilded and held close to the glass where the attraction of the water size pulls it from the squirrel tip and onto the glass.
- This process is repeated until the design area is covered. The gold will look rippled or uneven, so it should be allowed to dry thoroughly before the next stage.
- The drying process will draw the gold tighter to the glass and cause it to become smooth. Using a cotton ball, the gold should be brushed softly, removing any excess leaf and also burnishing the gold while you’re at it.
- Be careful not to brush too hard as this can cause the leaf to wear through or rub off completely. Once burnished, reapply more water size and gold leaf to any gaps and repeat the drying and burnishing processes until you are satisfied.
The same process is used for applying the silver leaf, though since it is a heavier metal than the gold, it will not be attracted onto the squirrel tip by static.
- Smear some petroleum gel onto the back of your hand, then brush the squirrel tip gently on the gel. The gel on the tip will hopefully hold the weight of the silver leaf before the silver is presented to the water-sized glass and attracted onto it.
- Repeat the same drying and burnishing process of the gold.
The fully burnished gold and silver will look very shiny through the front of the glass, though it will be very fragile on the exposed reverse side. It is necessary to protect the leaf by back-painting it. Try using a yellow signwriter’s paint on the gold and black on the silver, applying two coats for added protection and consistency of color.
So, there you have it! Hopefully, you have been able to learn something today, something that you can take away with you and share with the rest of the world.
FAQs Acid-Etched Gilding
Acid etching can cause permanent and, in some instances, irreversible erosion of the glass surface so you won’t have to worry too much about the designs losing their sharpness. However, to prevent wear and tear, acid etching is generally done on the side that is used less often, such as the back side of a door panel, so follow this advice accordingly.
The Acid Etch technique is a gilding technique that uses an acidic substance to cut into the surface of an object, most often glass or mirrors. This has often been utilized in classic pub mirrors, though this is but one of its uses.