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» Iconofile Forum   » Techniques & Materials   » Tools for Icon Painters--Part 1

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Author Topic: Tools for Icon Painters--Part 1
George
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Selecting the Right Sandpaper for Gesso

Gesso (chalk) grounds can be brought to a perfectly smooth finish with fine-grit sandpaper. Some types of sandpaper are not suitable, such as those with aluminum oxide and garnet, because the abrasive breaks down, leaving impurities in the gesso. Silicon carbide is a very hard abrasive and is used on wet/dry sandpaper.

The sizes of abrasive particles progress from coarse to fine as the grit numbers increase. Smaller and smaller grit reduce the scratches left by previous grit until they are no longer visible and the surface feels smooth to the touch. There are two standards for grit sizes: CAMI, the American standard; and FEPA, the European standard. The two standards are not equivalent in grit size for a given number. American grit sizes are about 10% finer below 180. Above 180 they diverge even more. You can tell what standard the sandpaper follows by looking at the markings on the back of the sheet. If the grit number is preceded by a "P" (coated abrasives), such as P600, or an "F" (bonded abrasives), it follows the European standard. American standard sandpaper only has the grit number, such as 400, 600, etc. For polishing the surface of gesso, begin with a 400-grit (P360 or F360) sandpaper, progress to 600 (P800), 800 (P1200), and possibly even 1000 (P1500) grit.

If the abrasive fully covers the surface of the sandpaper, it is called "closed coat." Open coat sandpaper contains less grit coverage on the backing to prevent clogging. Some manufacturers apply a zinc stearate coating to the sheets. The stearate acts as a dry lubricant to reduce build-up and helps lengthen the life of the sandpaper.

Paper is a common backing material available in five grades: A, B, C, E and F. A-weight is the lightest and most flexible grade used for hand sanding, orbital sanders and sheet sanders. Cloth backing is more tear resistant than paper and of the lightest of three weights--J, X and Y--J-weight is the most flexible for finishing and where conformity to shapes is important.

Summary: The best choice for hand finishing grounds is an A-weight, stearated, plain-backed sandpaper with silicon carbide abrasive.

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George O'Hanlon
Executive Director
Iconofile, Inc.
A nonprofit educational organization about sacred art

Posts: 911 | From: Northern California | Registered: May 2002  |  IP: Logged
George
Administrator
Member # 1

Icon 3 posted      Profile for George   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
Scriber: Since the 19th century, boards have been manufactured using woodworking machines that give surfaces a smooth finish. Hence, it was necessary to make incisions on the surface of the board; otherwise the ground may not adhere well to the wood. Incisions can be made easily with a special tool, called a scriber, which is not difficult to make at home or in a workshop. All that is necessary is a long wood block and a section from a metal hack saw blade. The dull edge of the blade is driven into one end of the block, in such a way that the serrated edge protrudes from the end of the wood block. Woodworkers in medieval periods split logs to make icon boards. After splitting the logs, a billet was further processed with an adze. Boards made in this manner were not very smooth, and had characteristic notches and gouges on the surface. These gouges gave a roughness to the board’s surface that fulfilled the same function as incisions. Therefore, there was no need to create a rough surface on the front of the painting panel in medieval times, and hence the absence of any description of this operation in ancient references.

Spatula: One of the most basic tools required to prepare a panel for painting is a spatula. A metal or plastic spatula can be used, but plastic is sometimes preferable, since metal can leave rust in the gesso. If it is more convenient to use a metal spatula, then the blade should be made from stainless steel. You may use a plastic rubber spatula, but the blade should not be too flexible. Some painters apply the first layer of gesso with a spatula, and follow it with subsequent layers applied by a wide brush. In this case, a brush with rigid hair, such as hog bristles, should be selected. However, it is preferable to apply all layers of gesso with a spatula, because a brush more easily creates air bubbles in the gesso. Air bubbles are difficult to remove from the surface of the ground and give it a dull appearance. This is undesirable, because as paint is applied to this surface the pinholes from air bubbles become more apparent giving the surface an uneven appearance. When the icon is coated with olipha or varnish, in these places appear tiny air bubbles, which are very difficult to get eliminate.

Surface Knife: To level off the surface of the gesso, it is necessary to use a putty or surface knife. Usually a stainless steel blade is sharpened and the corners rounded for this purpose. A straight surface with rounded corners is the only basic requirement for this tool. This is so that scrapes and indentations will not remain on the surface of gesso.

Pumice Stone: Many iconographers level the surface of the ground with the aid of pumice. Pumice stone in the form of long white blocks is best. The pumice stone should not be much larger than a matchbox. Smaller pieces can be used to make corrections in erroneously drawn lines of ‘prorisi’. The surface of the pumice stone must be even, which can be done by rubbing two pieces against each other. Select only the whitest pumice stones, since colored stones and stones with impurities can leave a deposit, coloring the ground.

Gluepot or Double Boiler: To prepare glue you will need a gluepot or a double boiler. Glue should be gently and evenly heated in a container placed in a water bath. You can use a stock pot and a tall can to achieve roughly the same affect. The can is placed inside the pot, which is filled with enough water, but not so much so as to cover the can.

Painting Bridge: For the painter to work in comfort with an icon of small size he needs a well-equipped and comfortable table. The table-top should be horizontal so that paint does not to flow down. Besides the painter needs painting bridges of different size—small supports and benches for the arm—so that the hand does not rest upon the icon, but on the support. The painting bridges allow the painter to hold the brush more vertically and accordingly to paint thinner lines.

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George O'Hanlon
Executive Director
Iconofile, Inc.
A nonprofit educational organization about sacred art

Posts: 911 | From: Northern California | Registered: May 2002  |  IP: Logged


 
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