Water Gilding


Water/Bolus Gilding Technique

Tecniques

The history of water gilding spans centuries and is closely intertwined with the evolution of artistic techniques, materials, and cultural practices. Water gilding, also called gilding on bole (doratura a guazzo, doratura a bolo in Italian) is a meticulous and refined method of applying thin layers of gold leaf to a surface using a water-based adhesive on top of a special ground preparation.

The Virgin Mary with Saints Thomas Aquinas and Paul about 1335 Bernardo Daddi (Italian, active about 1312 - 1348). Detail - Getty Museum
The Virgin Mary with Saints Thomas Aquinas and Paul about 1335 Bernardo Daddi (Italian, active about 1312 – 1348). Detail – Getty Museum

This gilding method has been the most valued for its ability to produce luminous and reflective burnished surfaces and intricate decorative designes achived with a variety of tooling techniques.

Water gilding materials

Materials & Tools

Let’s do some Alchemy!

To prepare the ground for water gilding yo will need:

GLUTINUM

Ichthyocol

Fish Glue, also known as fish adhesive or ichthyocol, is a type of adhesive that is derived from fish collagen, which is a protein found in fish skin, bones, and connective tissues.

It has been used for centuries as a natural adhesive in various applications, including art and craftsmanship.

The adhesive properties of fish glue made it suitable for securing the delicate gold leaf onto various substrates.

CRETA

Armeninan Bole

Armenian bole is a type of fine-grained clay that has been used since antiquity (see Pliny the Elder, The Natural History, cap. 28) in various applications including medicine and craftmenship.

During the Middle Ages and the Renaissance it was particularly used in gilding and painting. Cennini mentions it in various occasions.

Its reddish color is a result of the iron oxide it contains; the clay additionally can include aluminum, magnesium and other metals.

Although Cennini mentions Green Earth pigment as best gilding ground preferred by Giotto, in fact between XII and XVI centuries, red Armenian bole was the predominant choice for gilding purposes.

However, during the 17th century, both black and yellow bole gained traction in their applications. Black bole, in particular, found its use in silvering techniques and for sizable carved frames in the 17th century. Yellow bole began to be more frequently employed, especially in conjunction with non-burnished gold.

AQUA

WATER

Clean water, typically rain or spring water was used. We will use distilled water.

AURUM

Gold Leaf

The use of gold leaf dates back thousands of years and spans various cultures and civilizations. Gold has long been associated with wealth, prestige, and divinity, making it a prized material for artistic and decorative applications.

The production of gold leaf involves intricate processes to create thin, delicate sheets of gold that can be applied to various surfaces.

Thin sheet of gold, typically alloyed with small amounts of other metals to enhance its durability is placed between sheets of parchment to prevent it from sticking and then hammered repeatedly with specialized hammers. This process, known as “beating,” stretches and thins the gold into incredibly thin sheets.

he resulting gold sheets are cut into standard sizes or custom shapes, depending on their intended use. They are then carefully placed between sheets of protective tissue paper and packaged for distribution.

Different karat values (purity levels) and colors of gold leaf are available.

Water gilding process

Techniques

Step-by-step water gilding guide

There is more than one approach to water gilding. Cennini mentions different ways of preparing the size and some alternatives to Armenian bole. This step-by-step guide is compatible with period’s practices, as you can tell by comparing it to Cennini’s instructions also provided below, versatile and tested over time.

Preparing the Bole Ground


HOW TO LAY BOLE ON PANEL, AND HOW TO TEMPER IT. CHAPTER CXXXI

When you have finished modeling your ancona, get some Armenian bole and choose a good grade. Touch it to your lower lip: if you find that it sticks, that is excellent.

Now you will need to know how to make the perfect tempera for gilding. Take the white of an egg in a very clean glazed porringer. Take a whisk with several branches cut even and beat this white as if you were beating up spinach or a puree, until the whole porringer is full of a solid foam which looks like snow.

Then take an ordinary drinking glass, not too large, not quite full of good clear water, and pour it over the white in the porringer. Let it stand and distil from evening to morning. Then grind the bole with this tempera, as long as ever you can.

Take a soft sponge, wash it well, and dip it in good clear water. Squeeze it out and then rub lightly with this sponge, not too wet, wherever you want to gild. Then, with a good-sized minever brush, temper some of this bole, as thin as water for the first coat, and wherever you want to gild and where you have damped down with the sponge, lay this bole all over, watching out for the breaks which the brush sometimes makes.

Then wait a while, put some more of this bole into your little dish, and have the second coat stronger of color. And you lay the second coat of it in the same way. Again you let it stand for a while; then you put some more bole into the little dish, and put on the third coat as before, watching out for the breaks. Then put some more bole into the little dish, and lay the fourth coat in the same way: and in this way, it gets covered with bole.

Now the job should be covered up with a cloth, to shield it as far as you can from dust, sun, and water.

The craftsman’s handbook by Cennini, Cennino, active 15th century; translated by Thompson, Daniel Varney, 1902- ed

STEP 1, Prepare the Glue:

During the Middle Ages and early Renaissance, egg glair was primarily utilized as a bole size. However, during the Quattrocento, more straightforward techniques emerged, such as using hide or fish glue. What is common in these alternatives – a delicate very diluted glue should be used.

  • Soak 2g of fish gelatin (the one you can get in grocery store) in 150ml of cold water for about 15 minutes
  • Warm the gelatin and the water it socked in gently using a double boiler
Step 2, Prepare the bole:
  • Take Armenian bole ground in water. It has to be very thin: if you get it as dry pigment powder, grid it very thoroughly with distilled water on a slab, if you get it ready you might want to regrind it on the slab anyway to make sure it’s perfectly smooth. The amount depends on your needs (size of the surface you want to gild).
  • Put the bole paste (it should be pretty dense, like a dense yogurt) into a ceramic pot (don’t use metallic pots for bole as that might effect its electrostatic quality)
  • Gradually work the fish glue solution into the bole by mixing it thoroughly with a bristle brush. Add more glue little by little.
  • The consistency of the finished product is slightly denser than that of milk.
Step 3, Apply the bole:
  • The gesso ground of your panel has to be perfectly smooth and clean. Every scratch, grain or imperfection will be visible on the burnished golden leaf.
  • Once the under-drawing on a wooden panel, primed with a mixture of gypsum and glue, is finished, the outlines of the figures are incised using a metal point. This serves to delineate the regions designated for gilding from those intended for tempera painting.
  • Employing a wide soft, flat brush (synthetic hair will perfectly fit), a blend of bole and aqueous adhesive (fish glue in our case) is carefully applied across the designated gilding area.
  • The application is performed with careful attention to maintaining an even thickness and a continuous brushstroke in crossing directions.
  • This process entails repeating the application 4/5 times, each layer employing a progressively denser mixture. Wait for the previous layer to get fully opaque before you apply the next layer.
  • Wait for the bole ground to dry and sand it with a very fine grain sanding paper and/or linen cloth. Make sure the surface of the bole is perfectly smooth with no grains or scratches.
  • Now your bole is ready for gilding.

Applying gold leaf


HOW TO GILD ON PANEL. CHAPTER CXXXIIII

When some mild damp weather comes along, and you want to do some gilding, have this ancona laid out on two trestles. Take your feathers; sweep it oil thoroughly. Take a little hook; feel over the ground of the bole with a light touch. If there should be any foreign matter, or any little lump or grit, get rid of it. Take a piece of a strip of linen cloth, and burnish the bole briskly. Burnishing it also with a crook would be sure to help. When you have got it burnished and cleaned up in this way, take a goblet almost full of good clean clear water, and put a little of that white-of-egg tempera into it. And if it were a trifle stale, so much the better. Mix it up thoroughly with the water in the goblet.

Take a good-sized minever brush made out of the tips of the tails as I told you before; take your fine gold, and pick up the leaf carefully with a pair of tweezers or small pincers. Have a card cut in a square larger than the leaf of gold, trimmed off at each corner. Hold it in your left hand; and, using the brush with your right hand, wet down as much of the bole as is to receive the leaf of gold which you have in your hand. And wet it down evenly, so that there will not be any more water in one place than in another. Then carefully bring the gold up to the water on the bole; but have the gold extend a little bit beyond the card, just so that the little tip of the card will not get wet.

Now, as soon as you have brought the gold into contact with the water, instantly and quickly draw your hand and the little tip toward you. And if you observe that the gold is not all in contact with the water, take a bit of fresh cotton-wool, and tamp the gold down, as lightly as ever you can. And lay some more leaves in the same way. And when you are wetting down for the second leaf, take care to run the brush along the edge of the leaf just laid so accurately that the water will not run over it. And see to it that you lap the one which you are laying a little bit over the one which has been laid; first breathing upon the latter, so that the gold will adhere to the part where it overlaps.

When you have laid about three pieces, go back and tamp the first one down with the cotton, breathing on it, and that will show you whether it requires any faulting. Then fix yourself up a cushion, the size of a brick or tile, that is, a good flat board, with some nice soft white leather

The craftsman’s handbook by Cennini, Cennino, active 15th century; translated by Thompson, Daniel Varney, 1902- ed

Step 1: Prepare the “gilder’s Liquor”

The gilding size, also called “gilders’ liquor” is crafted from a blend of the identical fish glue solution, which is then diluted using a ratio of 1 part bole size (consisting of water and fish glue prepared for the bole) to 2 parts water.

Step 2: Managing Gold leaf
  • Gilding using loose gold leaf demands a delicate touch, given the lightweight and fragile nature of the sheets that can easily crumple with even the slightest movement. Precautions must be taken, such as closing doors and windows to prevent drafts and ensuring contact with the gold leaves is avoided.
  • The gilder’s knife must be degreased with alcohol, and the cushion (gilder’s pad) should not be touched directly, as it’s covered with a degreased calfskin. True gold sheet should only be handled with gilder’s tip and knife. Imitation gold can be touched by hand.
Step 3: Application of the Gold leaf

To apply the gold leaf:

  1. Hold the booklet of gold leaves above the cushion and use the gilder’s knife to place a gold leaf onto the cushion.
  2. Lay out the leaf on the cushion by using the knife while gently blowing on the gold from above in the desired direction.
  3. Cut the gold leaf into appropriately sized squares using a sharp gilding knife. Place the blade on the gold leaf, press slightly, and make a back-and-forth movement, being careful not to damage the cushion’s leather.
  4. Moisten the area to be gilded generously with water size using a squirrel brush.
  5. Use the gilder’s tip to pick up a piece of gold and lay it onto the wet size. Create static electricity by gently rubbing the gold on your hair to help it stick to the tip.
  6. Allow the gold to extend onto the bole. Gold leaf can be extended on the by employing controlled blowing and by tapping gently with a soft brush to remove air bubbles if they form underneath. To better attach the leaf you need to make a little cotton wool ball, blow on it to warm it up and then gently press the gold leaf to the surface.
  7. Repeat these steps until the entire gilding area is covered. Overlap the gold pieces to prevent gaps. If a gap appears, apply water size and another piece of gold. It’s important to ensure that the size spreads beneath the edges of the preceding gold leaf when applying the subsequent one.