How to execute water-based size gilding

Gilding Academy

Water-based size gilding with pure gold or silver leaf
Techniques and tools for the application of the water-based size

Water-based size is used for gilding the surfaces of objects with medium porosity (such as wood, plaster, stucco, paper and cardboard) that will go indoors. It is particularly suitable for:

• Wood frames
• Plaster
• Paper and cardboard
• Wood furniture
• Doors
• Wood coverings

Use water-based size to apply both pure gold and silver, loose or transfer leaf. In the latter case, using a sheet of tissue paper will facilitate grip and application, speeding up and simplifying the gilding process.

For imitation leaf gilding you will find more information here

Base material preparation

Tools:

• De-waxed shellac (or other paint) to reduce size absorption
• Sandpaper for smoothing
• Acrylic colour (optional) to add colour to the background

In order to ensure good adhesion of the size and to make sure it does not absorb too rapidly, the surface where the size will go mustn’t be too porous. If it is, it is important that you apply a layer of de-waxed shellac or another paint first, which should be chosen according to the surface material.

Sand the surface with fine-grained sandpaper to make it as smooth as possible.

To make the end result of the gilding warmer and more homogeneous, you may also apply an acrylic colour on the surface (usually yellow or red for gold, and grey or black for silver) and sand the surface with fine-grained sandpaper before applying the size.
Application of the water-based size

Tools:

• Water-based size
• Brush with soft hair

With a soft hair brush or pad, spread the size as thinly as possible. The smoother and more compact the surface, the smaller the amount of size required to make the leaf stick. Too thick a coat would lead to the size drying with imperfections, especially in the depths of the coat, and then you may also see bubbles, wrinkles or cracks on the gilded surface, which would compromise the end result.
Drying the water-based size

Water-based size has different drying times depending on the type you are using. Once dry you can proceed with the leaf application. To assess if the time is right, we recommend touching the area with the back of your hand. It must be slightly sticky but without leaving a damp residue on your skin and without detaching from the piece you are working on. We do not recommend touching the surface with your fingers, to avoid leaving prints on the size that would remain visible even after you’ve gilded the surface.

It is important that you be very careful when evaluating the right waiting time before applying the leaf. It normally takes 10 to 45 minutes, depending on the type of water-based size. If you wait too long there is a risk of it drying completely, which would not allow the leaf to adhere. Then again if you do not wait long enough, applying the leaf will stop the drying process of the size, resulting in unstable gilding. Humidity and room temperature are two other factors that significantly affect drying time.
Leaf application

Tools:

• Loose or transfer gold or silver leaf
• Gilding cushion
• Gilding knife
• Squirrel hair gilder’s tip
• Cotton pad or Kolner cloth

To apply the loose leaf, gently open the booklet and place it onto the gilding cushion. With the help of a gilding knife, slide the leaf onto the cushion and apply it by blowing gently on it. It is essential that the leaf never comes into contact with your fingers to avoid damaging it and making it unusable.

The gilding knife is also useful if you only need a portion of it and you need to cut it.
To facilitate gilding application, we recommend using a squirrel hair gilder’s tip. There are different sizes, which vary according to the size of the leaf.

When it is not necessary to cut the leaf and especially when gilding flat surfaces, we recommend using transfer leaf. Simply remove the leaf from the booklet, lay it – facing downwards – on the surface you are gilding, apply light pressure on the tissue paper, using padding (like a cotton ball) and gently remove the tissue paper, which will detach smoothly without clinging to any metal parts.
Protective coat

Tools:

• Brush with soft hair
• De-waxed shellac or synthetic protection

Once the leaf has been applied, a finishing varnish can be applied to the decorated surface which will help to preserve it from damage. The protective coat is optional when working with high purity gold leaf. We always recommend it, however, when gilding with silver leaf or with gold leaf that has a high quantity of silver in the alloy because there is a risk of oxidation.

Apply one or two coats of de-waxed shellac natural varnish, using a soft brush, and wait for the first coat to dry completely before proceeding with the second.

So as not to alter the colour of the silver leaf, you should preferably apply an extra-clear de-waxed shellac or another transparent protective varnish.

Before proceeding with a protective coat, it is important to know that it will in any case change the appearance of the leaf in terms of colour tone and glossiness.


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