What is Oil Gilding? A look at techniques & materials

Icons are often – but not always – gilded, that is finished with gold leaf. Some indeed are completely covered in gold leaf and then painted over – years ago I tried this technique in the mandorla around Christ in the icon of the Transfiguration which is now in the parish of the Archangel Gabriel in Glasgow. Normally, as in the icon of St Andrew which is now in Christ Church Cathedral in Hartford, Connecticut (USA), the painted area is left ungilded for the gesso to shine through the layers of paint.

 

It’s not a simple technique but (with careful application of layers of paint over either garlic juice or ox gall liquid) it is possible and the result has a warmth and glow that enlivens the finished icon.

Oil size

Oil size is a tacky, sticky varnish which comes in different ‘open’ times – 3 to 12 hours are the ones I have worked with. In Scotland, however, I find the times are notional!

First the board must be sealed with shellac varnish – only where the gold leaf will sit. This needs to be applied to a completely smooth board, and then carefully applied with a fine synthetic brush like this one  (not an affiliate link). I use this for both shellac and size, with a thorough clean in either white spirit or methylated spirit as required. 

I have to say that oil gilding is a stinky job in a different way to the smells of rabbit size from water gilding. The shellac, the size, the brush cleaners (which are not eco-friendly so must be disposed of at your local authority waste centre) all smell strongly so go carefully: I do not go so far as wearing a respirator but the windows must be open.

Next, once the shellac layers have dried thoroughly, carefully apply the oil size using the same or a similar brush, brushing it out thinly and evenly. Common errors include making the size too thick or not brushing it out carefully and thinly.

Use a clean, dust-free (or minimally dusty) environment and (from bitter experience) do not wear fluffy or knitted garments – an old fine cotton shirt makes a good smock replacement. The hardest part is waiting – I have seen three hour size stay open for gilding for almost 12 hours in my cold, rather damp Scottish house, while I know friends in Greece struggle to get the gold laid down in time! If possible, make a few test boards, with different ‘times’ of size and on different days, so you get a good feeling for when to begin checking without leaving finger prints.

small round container showing golden yellow oil size
These pictures show the oil size before (left) and after (right) use – hardly any has been used to gild two board. Always decant the size from the bottle, don’t put the brush in.

To check if your size is ready you have a choice, based on experience:

– carefully drag a finger knuckle lightly across a tiny area (if it grips or drags, too soon; if it squeaks (quietly) go ahead

– judge by sight: the size suddenly changes and appears tight, almost floating, on the surface.

Gilding too soon is the most common error, by far. This is another time when practicing is your friend along with patience.

When ready, lay the gold leaf. You can use either transfer (attached to a piece of thin paper) or loose leaf.

– transfer leaf can sometimes leave the imprint of the paper on the finished leaf and marks when laid on soft size are common.

– loose leaf can be laid with gilder tip brushes after being cut to size with the gilder knife on a pad: it is a similar process to water gilding but of course with the peril of a stray hair being caught on the size if the tip is too large or strays onto the gold.

– there are advantages to both: the most important factors are the thickness of the leaf, experience, patience and maintaining just enough pressure to adhere the gold.

All of the materials needed can be bought in a kit form directly from Wrights of Lymm, which makes it easier to start with (not an affiliate link).

Finally, after applying gold leaf as carefully and thoroughly as possible, making sure not to leave any gaps between pieces which will be bare when the size has dried and cannot be repaired, lightly tamp the gold down with a squirrel mop reserved for gilding. Cotton wool can leave tiny fibres and fluff, so is not really suitable. Lightly, gently, ensure the gold has adhered to the size. It’s not necessary to remove any excess at this point although if there are a lot of small pieces in a complicated shape, it will show the remaining gaps. These grow less with experience. The longer the size is left to harden, the better shine can be achieved.

The whole process is relatively quicker than water gilding, as it is not possible to burnish with an agate and cannot achieve the mirror smoothness which has become fashionable recently. The finished surface remains fragile for up to one month, depending on the size used, so should be protected from oil, dirt and abrasion: if the icon has to be painted immediately, then a paper ‘mask’ over the gold and resting the painting hand on either a support or (if painting flat) some books or a bridge are ways to prevent any damage to the surface. There are additional steps you could add, including a fine wash over the board of red pigment to mimic the glow of red clay/bole under water gilding, adding warmth – finding one which is not gritty takes research; likewise, some sand the coats of shellac (which may not be required depending on its thickness and the method of application). Personally, while I understand the attraction fof highly burnished gold leaf (shiny! bright!) I am not sure that I want icons which look like mirrors, when praying in an icon corner or church. A mellow, soft finish will reflect candlelight while not outshining the painted face or distracting us with our own face, staring back. Which do you prefer? Let me know!

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