Step I

Surface Preparation for the Sinopia Clay Bole

The ideal surface for water gilding is a rigid wooden surface. Since both gesso and bole are fragile layers, this style of gilding is not suitable for flexible surfaces such as canvas or paper. There are some examples of small water gilded areas in illuminated manuscripts, but that type of gilding requires a few extra steps. Even though preparing gesso is a labor intensive process, it is worth the effort. Once you have experienced the smooth velvety absorbent finish of a traditional chalk ground, no other gesso will compare.

Please note: this is a basic tutorial on how to apply a traditional chalk ground and how Sinopia Clay Bole can be used. Watergilding is a craft that can take years to perfect and these instructions are meant to serve as a starting point, not a comprehensive course. Additionally, all proportions and directions have been compiled from our experiences with our products and may be different from other guidelines that are taught and published. Working with these organic materials is very much like cooking, where no two recipes are alike.

We would like to thank Joel Hoyer, for sharing his recipes and opening up his gilding atelier for this tutorial.

For a more detailed recipe, please view our Sinopia Clay Bole Poliment Technical Data Sheet

Rabbit Skin Glue Recipe

We recommend rabbit skin glue for our chalk ground recipe, but hide glue also works. We recommend a ratio of 1 part glue to 15 parts cold water. Combine these two ingredients in a container that can be heated and let the glue soak overnight.

Warming the Glue

Rabbit Skin Glue always needs to be used warm. Once the glue granules have been soaked into the water, gently warm the mixture on a temperature controlled heat source or a double boiler. Do not allow the glue to come to a boil

Applying Fabric Layer

There are many recipes that skip this step and we advise against that omission. Having a layer of fabric between your gesso and the wooden substrate, creates a buffer which affords the fragile gesso protection from whatever expansion and contraction the wooden substrate will experience with seasonal changes.

Sealing the Panel

Before adhering the fabric to the panel. Dilute some of the Rabbit Skin Glue Solution by 100% and liberally apply the thinned solution to all sides of the panel. This prevents uneven moisture absorption and thereby protects the panel from warping.
*Most wooden surfaces work for gilding. Examples of suitable substrates are wooden panels made of birch, oak or mahogany. Larger panels should be cradled with cross braces, in order to prevent warping.*

Adhering the Fabric

Once the glue has been applied, take the fabric and dip it into the full strength glue solution. Pull the soaked fabric out with tongs and spread the fabric flat onto the panel.

Fabric Note: it is best to use natural fibers such as cotton or linen for this application. If using material from the fabric store, wash the fabric first to get all of the starches out of the weave, which cause wrinkles if left in the fabric. Recycled all cotton bed spreads are a great fabric choice.

Smoothing the Fabric

Once the fabric has been spread out onto the panel, smooth the surface to ensure that there are no bubbles under the fabric.
*The fabric can be applied to just the front of the panel, or it can be wrapped around the edges and even cover the back of the panel.*

Wrapping the Panel

This step is optional: if wrapping the fabric around the back, apply more glue onto the back of the panel and fold the fabric. Allow the glue to dry thoroughly, before proceeding to the next step.

Preparing the Gesso

Measure out 3 volumes of the prepared rabbit skin glue solution into a container that can be heated.

Adding the Chalk

Gently sift two parts French Chalk into the warm glue solution. For toned grounds, substitute 1 volume of chalk with a pigment such as red earth, umber or black.

Blending the Gesso Ingredients

As the chalk is added to the rabbit skin glue solution, continually stir the mixture gently, in order to prevent the forming of air bubbles in the gesso. Once the desired consistency has been reached (we like a heavy cream consistency, but the gesso can be made thicker with more chalk), the ground is ready to be applied.

Applying the Gesso

Use a brush with firm bristle to apply the first layer of gesso with unidirectional brush strokes. This layer will absorb into the fabric and not cover the fabric. This layer is not about building up the surface, but about creating a foundation for the subsequent layers.
Brush Note: For application use a brush that has a suitable size for your panel dimensions. Avoid giant brushes, because controlling the flow from the brush can be difficult. If the brush is too small, then gessoing will take forever. We prefer natural bristle brushes such as hog or ox hair bristle, but synthetic brushes will work as well.

Applying the second coat of Gesso

Once the first layer has dried, the panel is ready for the second coat. The layers of gesso take about 5-10 minutes to dry, before they can accept the next application.

Applying Gesso layers

Once the previous layer has dried, apply the next layer with brush strokes in a perpendicular to the previous layer. We recommend a minimum of at least 3-4 layers, but most gilders will apply 8-10 layers of gesso. Once the gesso has completely dried, it can be sanded for a smooth finish.
Gesso Note: During the application, it is necessary to continually stir the gesso gently on the heat source, because the chalk likes to settle at the bottom of the container. Once again: stir gently, so that you do not wisk air into the gesso.

Step II

Preparing and Applying Sinopia Clay Bole

Sinopia Clay Bole Recipe

This recipe is meant to serve as a starting point. Once the bole is mixed and applied, it is susceptible to such atmospheric conditions as temperature and humidity. Therefore a bole recipe that yields great results in New York, will not work in Santa Fe, because the weather conditions are completely different. Additionally, bole recipes are adjusted for different types gilding, such as highly reflective burnished surfaces or more subtle polished gold.

Preparing the Sinopia Clay Bole

Place a small amount of Sinopia Clay Bole into a heatproof container.

Thinning the Sinopia Clay Bole

Slowly add cold water to the bole and integrate the water into the bole with a spatula or stiff bristle brush.

Proper Sinopia Clay Bole consistency

Keep integrating water, until the bole/water mixture reaches the consistency of a heavy cream.

Integrating Rabbit Skin Glue into the Sinopia Clay Bole

Slowly add approximately 10% prepared warm Rabbit Skin Glue to the Sinopia Clay Bole. The mixture will start to thicken right away.

Warming the Sinopia Clay Bole

Place the mixture onto a heat source and gently warm the Sinopia Clay Bole. Slowly add small amounts of water, until the bole becomes a brushable consistency.

Applying the Sinopia Clay Bole

While the mixture is warm, apply the Sinopia Clay Bole onto the previously prepared Gesso surface. Brushstrokes should be applied in one direction.

Applying additional Sinopia Clay Bole layers

Once the bole has dried, apply additional layers to the panel. For a smoother surface apply subsequent layers with brush strokes that are perpendicular to the previous layer. 3-4 layers of Sinopia Clay Bole are sufficient. Now the panel is ready for gold leaf.

Step III

Applying & Burnishing Gold on Sinopia Bole

Applying Gold Leaf onto Sinopia Clay Bole

Once the Sinopia Clay Bole surface has been prepared, gold leaf can be applied and burnished. While achieving highly reflective gilded surface can take years of practice, the Sinopia Clay Bole is user friendly enough, so that even novices can achieve beautifully polished surfaces.

Contrary to popular belief, when a gilded surface is burnished, it is not the gold leaf that gets polished, but the soft clay surface beneath the leaf. It is therefore crucial to find a perfect rabbit skin glue ratio, that is strong enough to hold the gold to surface, but not too strong, so that the Sinopia Clay Bole is no longer pliable enough to burnish.

Preparing the Gilder's Liquor

In watergilding, the dried bole needs to be reactivated before the gold leaf is applied. This is accomplished by flooding the bole with a gilder's liquor. A standard blend consists of 1 to 2 parts denatured or isopropyl alcohol to 8-9 parts cold water. The mixture is then applied with a gilder's mop, which draws in a generous amount of water and quickly releases the liquid onto the surface.
*Some gilders add a diluted rabbit skin glue to the mixture, in order to improve adhesion. This step is optional.*

Flooding the Sinopia Clay Bole

Generously apply the water mixture onto the prepared bole. The addition of the alcohol in the mixture prevents the water from beading up. When the bole is flooded, it becomes pliable and the rabbit skin glue is re-activate and acts as the adhesive for the gold leaf

Preparing for the Gold Leaf

There should be so much water on the panel, so that the water puddles on top of the bole. Once this has been accomplished, it is time to float the gold leaf onto the water.

Laying the Gold Leaf

With aid of a gilder's tip, gently lay the leaf onto the surface and allow the gold to float on the water. As the water continues to soak into the Sinopia Clay Bole, the leaf will be drawn down onto the surface.
*Watergilding can only be performed with surface gold, that is not adhered to a transfer sheet, as gold is in patent leaf.*

Burnishing the Gold

Once the gold has been applied, the bole will start drying again. As the bole surface dries, it will reach a window, during which time the optimum moment for burnishing is reached. To ascertain this moment, gently tap the burnisher onto the surface. In the beginning, the sound will dull, as the wet bole absorbs the sound. Once the tapping sounds hollow, it is time to burnish.

The Burnished Surface

Once the gold has been burnished, it will yield a reflective surface. If the gold comes off during burnishing, then the burnishing started too soon and/or the glue strength is too weak. If the surface becomes scratchy during burnishing, then the burnishing commenced to late and/or the glue strength is too strong.

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