Crude glass mirrors can be traced to the 3rd century A.D. when gold leaf was attached to the back side of a piece of glass. Relatively good glass mirrors were produced from the 12^th century in Venice by placing a polished metal plate behind a sheet of clear glass.

By the 16^th century, a process had been developed to apply a thin amalgam of tin and mercury directly to the back side of a sheet of glass to produce a much improved mirror. This was the principle process used for mirror production for several hundred years until around 1835. In that year a process for treating glass with a thin layer of silver was perfected by Justus von Liebig. The silver technique produced a mirror with significantly greater clarity and brightness than the tin/mercury mirror and quickly displaced the older process.

Glass, and mirrors in particular, were still relatively rare in late colonial America. As a result, it became common practice in the late 1700's and early 1800's to install a large mirror in the door of wooden works shelf clocks. This increased both the value and utility of the clock which, hopefully, stimulated sales. Clocks produced prior to 1835 would, of course, have used mirrors produced using the older tin/mercury process. These early mirrors are clearly distinguishable from later silver process mirrors in that they have a softened patina that reflects light more subtly than silvered or modern mirrors.

Due to the inherent dangers of handling mercury, it is very unlikely that a source for creating an original tin/mercury mirror will be found. To create or restore one of these early tin/mercury mirrors, an alternative technique known as Eglomise can be used. Eglomisé is the process of applying gold or silver leaf to the reverse side of a glass object. Applying silver leaf produces the soft reflective surface seen on original tin/mercury mirrors.

The following presentation covers the application of silver leaf to a glass in order to create or repair an early tin/mercury mirror.

There are many different techniques that can be used to apply leaf to glass. Web sites such as Murals Plus have some lively discussions about techniques for gilding on glass.

Martha Stewart has a good presentation on her web site for using the Eglomise technique to create a mirror.

Well known NAWCC member Lee Davis has, for many years, taught a highly regarded course on reverse glass techniques including eglomise.

The technique presented here is only one of the many possible. It was chosen because it can be quickly perfected by a restorer without previous gilding experience and it doesn't require the purchase of a lot of special tools that may go unused for long periods.

Gilding on glass is a skill that the average clock restorer can master. It does, however, require some practice to master the techniques. Please read this entire presentation before attempting a project. It is strongly recommended that a small "practice" glass be used to work out the finer points before attempting a full sized project.

The materials needed for creating a mirror are:

1. An appropriately sized piece of antique (wavy) glass.
2. One or more "books" of silver leaf.
3. A package of gelatin capsules.
4. A bottle of distilled water.
5. Alcohol (denatured or isopropyl)

1. A pan large enough to allow the glass to rest in it.
2. A new one-inch, soft bristled paint brush.
3. Wooden blocks to brace the glass on an angle.
4. A roll of waxed paper
5. A soft felt cloth.
6. A can of Bon Ami cleanser.
7. Acetone.
8. Cotton balls.

Dry the glass carefully with lint free rags then wipe both sides with acetone.

Inspect the cleaned glass carefully in good lighting. Scratches in the glass will be even more visible once the silver is applied. If there are small scratches, make sure they are on the un-silvered side of the glass.

Place the cleaned glass between paper towels until needed.

Gelatin size offers several advantages over other types of adhesive.

   It dries crystal clear.
   It shrinks when it dries which helps to remove wrinkles.

Empty gelatin capsules can be purchased from health food stores such as Hi Health and some pharmacies. Food gelatin powder can also be used, but clear capsules dissolve quickly and dry crystal clear.

Notes about gelatin size:

  -  Overly strong size will dry cloudy and become worse with age.
  -  Weak size will lift and bubble when the second gild is applied.
  -  Gelatin glues break down with over-heating or boiling.
  -  Poor quality water will cause cloudiness in the size.

Pour about 1/4 cup of distilled water into a clean glass measuring cup.

Remove the halves of one capsule from one another and place in the water.
 
Allow the capsule to soften for a few minutes then use a spoon to gently agitate the water until the capsule pieces are totally dissolved.

In a second cup, heat about 1 cup of distilled water to a hot, but not boiling state.

Pour enough of the warm water into the glass measuring cup to make up the total one-cup volume. Add about 1/2 tea spoon of alcohol to make the water less "clingy". Stir and allow to stand.

Note: It is not necessary to keep the sizing mixture warmed. It can be used at room temperature.

It is a thicker material than real silver leaf which makes it somewhat easier to handle. It tends to be slightly less reflective than real silver and may retain more wrinkles.

It is, however, an excellent material for developing you skills and techniques and, depending on the application, may be a good choice.

Transfer leaf is the term used when each leaf is attached to a sheet of tissue or backing paper. Transfer leaf is most often used when working outside where the slightest breeze would easily blow a loose leaf away.

A form of transfer leaf is used in this process because it allows an easier to master technique than simply lifting a loose leaf with a gilder's tip and dropping it on the glass.

Transfer leaf is easily made from a book of loose leaf by first cutting squares of waxed paper to a size slightly larger than a leaf.

Cut a supply of waxed paper squares but don't put a leaf on a sheet until you are ready to lift it and apply it to the glass.

Place a suitable block in the drip pan to allow the glass to be positioned on a slant. It helps to place some tape (that has been doubled over ) on the blocks so that the glass stays in position.

Size can be brushed onto the glass or simply poured. The excess size will run off of the glass into the drip pan.

Carefully position the leaf and waxed paper over the glass and slowly lower into contact.

Work from the center outward to remove wrinkles and size. Do not become over aggressive or the leaf may tear.

Very gently lift the waxed paper and discard.

It is not necessary to get the leaf perfectly wrinkle free. That will be done with the felt rag once the size has set up.

If tears do develop in the leaf, don't worry. This will be deal with in later steps.

Be careful about disturbing the first leaf.

If there are holes in the coverage, use a small brush to apply size. Use partial pieces of leaf to cover the holes. Small pieces of waxed paper can be used to press the leaf down.

Allow the size to cure for several hours or over night.

Wrap the felt rag over a finger and (beginning in the center of of the glass) gently burnish the silver with the rag. Go slowly and use light pressure.

You will actually be able to see the silver become smoother and small wrinkles will disappear. Continue working from the center outward until most of the wrinkles are removed.

You may remove some leaf with the rubbing. It will be covered with the second gild.

Lift the glass and view from the front side. The image should now be noticeably brighter and clearer.

The sizing can be made to only 1/2 the strength used for the initial gild. That is one capsule to 2 cups of water. Again, add 1/2 tea spoon of alcohol to make the size flow.

Use a soft brush to apply size to the glass and apply leaf exactly as before.

To cut leaf without tearing, place it between two tissues from the book then lay a stainless steel ruler across the line of cut. If the ruler has a cork backing, turn the ruler over so that it rest tightly against the tissue.

Use a new hobby knife blade to cut through the two tissues and the leaf.

If a brighter mirror is desired, some craftspeople carefully pour hot (almost boiling) water onto the front (un gilded) side of the glass. Care must be taken to avoid burns and the water should not be allowed to touch the back side of the glass. This technique will usually produce a noticeable brightening of the mirror image.

Backing: Some type of backing must be applied to the silver to provide protection and prevent oxidation of the leaf. A dark water-based acrylic paint works well for this. Asphaltum can also be applied to the back of the glass for an authentic look and feel.

This restoration technique takes a delicate hand and some practice, but is well within the skills of the average restorer.  A few practice pieces are usually all that are needed to master this very useful skill.

If you decide to give it a try, take some photos of the finished piece and pass them along.

Tom T