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Panels - Special grounds upon which to paint
(in addition to other arty things such as gild with Pt, Pd, Au, Ag, Al, Cu and so on)

Paintings have to be painted on something and there are plenty of things to choose from: walls (frescos and so on), the pavement (which is what I did professionally for a number of years in the 1980's) and then something to hang on your wall that allows you to view an alternative universe or an idealised version of our own. Originally, the frame had three moulded edges - the stiles and the upper rail - whilst the lower rail was an inclined sill - like the bottom of a window frame. At the time - up until the latter half of the fifteenth century - works were painted on cross cut oak panels. Only later was canvas stretched in a frame adopted as the main ground for paintings.

The one thing that using solid cross-cut oak as going against it is the weight of a panel once you get above a certain size. For smaller paintings - up to, say, 50x60cm, the weight is reasonably low - for larger panels, you just have a stronger frame and there are plenty of examples of larger panels around such as alterpieces, Elizabethan portraits and so on.

As for the width of the panel, you can source 25cm wide solid quarter cut oak panels online nowadays, from people who do nothing else so, you know that they know what they are doing and that you will get the right thing.
Quarter cut oak, showing the medulary rays. Copyright (c)2017 Paul Alan Grosse       

This is a piece of untreated, planed all around quarter cut oak that is roughly 10" x 12" (25 x 30cm) and 9mm thick. This is a nice size to work with as working on it can be done either on the studio easel or on the desk - depending upon what I'm doing with it.

The amount of water in the panel needs to equilibrate with that of the moisture content in the climate that the picture is going to hang in when it has been finished. I bought three of these panels so that I could have a play around with them.

I started off by putting them together and leaving them overnight. The following day, the outer two had lost sufficient water from the outer surfaces to curve them very slightly - a displacement from straight of around 2mm, across 250mm. So, I turned them around so that the outer faces were now facing the inner piece and the following day, they had straightened out again. So, over the next three weeks, I had them out of the way, positioned so that air could circulate all around them individually so that they could equilibrate with the level of moisture in the room.

Quarter cut oak, showing the end of the grain of the panel. Copyright (c)2017 Paul Alan Grosse       

Here, you can see the end of the grain of the panel. Notice that the rings only run perpendicular to the surface of the panel. In this way, if the moisture content of the air changes, the panel will expand or contract the same on the front of the panel as the back so it will not warp. With wood the darker parts of the rings and the lighter parts expand or contract differently with changes in moisture content so here, where they are in effect, all stacked up across the panel, there is no bending of the panel.

This type of cut is done by taking radial cuts from the trunk of the oak tree. The medualry rays are also radial so with this cut of oak, you can see the figuring quite well although it is worth noting that each oak tree differs in the amount of figuring that you can see.

The Italian panels of this period, were cut across the trunk so that in the middle, the rings flip over to face the other way in the way that the bowl of a spoon curves and as a result, when the moisture levels in the air change, making the wood expand or contract, they 'spoon' and twist. One way that they tried to reduce this effect was to dig out the surface where the most curvature would happen and replace it with some wood that was less likely to warp. Conisdering that the Italian renaissance was roughly a century behind the north European renaissance, you would have thought that they could at least have learned about quarter cut wood.

Using a mortice gauge to mark the thickness of the edge after bevelling - remember, no pencils. Copyright (c)2017 Paul Alan Grosse       

One thing to remember is that the pencil was not developed until the end of the fifteenth century so using it is out of the question. Instead, and in effect, using something that is better than a pencil under these circumstances, I use a mortice gauge which has three very sharp pins in the end - one on one side and two on the other, so that you can mark the thickness of the wood that is left at the end of the process of bevelling - ie, thinning the edge of the wood so that it fits nicely into the rebate in the frame.

Quite a shallow angle is used for the bevel as we want to present what is in effect the edge of a thinner sheet of wood to the rebate.

Quarter cut oak cut to make panels for painting, showing the bevelled edges of several panels. Copyright (c)2017 Paul Alan Grosse       

Here, you can see the bevelled edges of the panels, showing how wide an area is taken off the back ...

Quarter cut oak panels, showing the how they fit in the solid oak sloping sill, cavetto frames. Copyright (c)2017 Paul Alan Grosse       

... and here, you can see three solid oak, sloped sill cavetto frames with two of the quarter sawn oak panels in them - one showing the back of the panel, demonstrating how little room is left between the panel and the moulding (I leave around 1mm) and on the other, you can see the front of the panel, in the frame.

Note that I have already put the chord for hanging and its two fittings on the frame - this is because it makes it easier to handle the complete unit.

One thing that is worth making a point about at this stage is that it was the habit of the early 15th century and before to paint the picture already mounted in its frame. This had the effect that it made it easier to paint items that crossed or abutted the boundary between the painted world that the panel occupies and the real world that the frame occupies. In many paintings, cloth or fingers cross from painting to frame and it makes it all that more an interesting experience for the viewer, instead of having the two realms strictly isolated.

As a result of this habit, you can see examples of work where, for one reason or another, the panel has been removed from the frame, where the edge quarter of an inch or so is either completely bare or only has the size or gesso ground on it. This raises the question of do you want to put the panel is its frame before sizing both, after sizing but before applying the gesso to both, before painting but after gessoing the panel and frame or after it has all been completed.

Many paintings that have not been removed from their frames have a seamless surface running from the panel to the frame and this also eccentuates the illusion that the reality of the painting on the panel is permitted to escape into the real world of the frame whereas a gap would force the artwork on the panel into isolation.

Quarter cut oak panel, sealing it with size. Copyright (c)2017 Paul Alan Grosse       

Next, we need to seal in the wood so that it doesn't interact chemically with the paint that eventually, we are going to paint for the viewer to see. In this case, it is with a size made from acacia gum - also known as gum arabic. This comes either in the form of chunks of resin that have to be soaked, dissolved and then filtered or, as in this case, a pure, powder that just has to be dissolved.

In either case, you shouldn't allow the container to come into direct contact with the flame because it causes decomposition of the gum so, you have a pan of water and sit the solution in another container within that - a porringer or 'bain marie' as some people seem to know them. In that way, it cannot get hotter than 100C although in practice, I found that it didn't need to get any hotter than around 50C.

I found it useful to put a tiny amount of red bole in it so that I could see where it had been painted. A nice, quick, even coat with this and then I allowed it to dry.

Next, I added some calcium carbonate powder to it and a little more red bole to keep the colour and then painted that on, taking care not to leave any brush-strokes on the surface.

After that, I added more calcium carbonate to the size but not the colour - this meant that it was substantially lighter in colour - and painted that on with the brush strokes going perpendicular to the strokes of the previous layer. Subsequent layers were all of this lighter coloured gesso.

Quarter cut oak panel. Drying out the gesso in a temperature controlled fan oven. Copyright (c)2017 Paul Alan Grosse       

When I was satisfied that there was enough gesso on the panels, I placed them in the electric fan oven and dried them at around 27C - our oven will go that low with the door shut and although it doesn't give a number on the dial, it does control at that temperature although I would recommend that anybody trying this uses an infrared thermomenter like the one in the photograph to monitor the temperature. The reason for having the door open when looking at the temperature is that if you pointed it at the closed door, it would measure the outside of the door, not in the oven and with a triple-glazed door like this, that could result in a serious error.

Using a fan oven at 25C-30C means that:

  • the temperature is the same as it would be in the middle of summer and so is not excessive for the materials used to make the panels; and,
  • the forced draught accelerates the evaporation process which, apart from making the next step sooner (for the hedonistic artist) but it also means that the oak has less opportunity to absorb the water.

Once it has all dried out, I sanded the surfaces down with medium and then fine sand paper, using a block so that I got a flat surface.

If you were wondering why I coloured the first coat of gesso, this is where it becomes apparent - or hopefully not. If at the sanding stage, you manage to get through to coloured gesso, you know you only have a small amount left before you hit wood and therefore you know that you have gone - or are about to go - too far.

Quarter cut oak panel. scraping a shine onto the panel. Copyright (c)2017 Paul Alan Grosse       

This next step is a bit odd but it is what has been done for centuries and it works extremely well.

Using a scraper, scrape the surface away until it is all shiny and flat. This leaves a very flat surface that is actually cold to the touch.

The scraper itself is an ordinary decorating scraper but looking at the variable quality of these things, I would recommend going into a hardware/decorating shop and selecting one based on how smooth the edge is - any irregularities will translate to scrape marks all over your panel's ground.

Finished gessoed quarter cut oak panel. Copyright (c)2017 Paul Alan Grosse       

This is the final surface. It is cold to the touch and as there have been no oil-based processes involved in its making - the only thing we have used has been acacia gum - you can still do water gilding on it if you want, or you can seal it with some linseed oil before painting on it

As there were no pencils at the beginning of the fifteenth century, the tool to write with is a plummet - a point made from lead. Here, I have used a bit of spare 1.5mm thick lead roofing cut into a triangle. This writes very well on the surface and if you leave it for a long time, it converts to lead carbonate which is, of course, lead white and it becomes very difficult to see.


All images and original artwork Copyright ©2017 Paul Alan Grosse.


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