An oil pastel has the pigment bound with non-drying oil and wax. Quite different results can be achieved using a variety of techniques. For example: oil pastels dissolved with solvents look very different to ones used lightly over the surface of a textured paper. Some wax or oil pastels are also water-soluble. Some artists use fixative to protect the work as the colour remains somewhat smudge-able but mounting and framing behind glass is usually sufficient protection from smudging.

A soft pastel is made to be as soft as possible without falling apart or breaking too easily. The surfaces used with soft pastels usually need to have a tooth to hold the powdery colour onto the surface. Because colours are mixed on the surface and not mixed on a palette beforehand pastels usually come in a huge range of tints and shades of colours. Finished paintings should be sprayed with a fixative for
longevity as the soft colour may not adhere completely to the surface (especially if many layers are built up) and framed with a mount and glass to protect the work, though some artists do not like the look of fixative and simply frame the work. Soft pastels can be used dry or with water and also come in a pencil format that is tidier to use.

Hard pastels are usually square and are often called carre crayons. They have been baked at a higher temperature and their hardness allows finer lines to be made with their edges. Like all artist materials the quality of a pastel is measured by the amount and quality of pigment and the higher quality pastels have little or no filler and the minimum amount of binder required to hold the pastel together.

Every artist develops a preference for a particular brand, often based on colour choice or level of softness or hardness. A beginner would be wise to buy a colour in each brand and as they need to replace each colour buy the brand they have come to like best. Pastel painting is usually done on pastel paper, which comes in a variety of colours and textures, though there is a textured ground for pastels by Golden Acrylics that can be painted on primed wood or canvas so that those surfaces can hold the pigment from soft pastels.

Watercolour Papers
Watercolour paper has a “hard size” on top of the paper that allows the water to penetrate and the pigment to remain on the surface. This gives the painting its brilliance and also allows for corrections.
Watercolour paper comes in different textures. ‘Hot Press’ (HP) is the smoothest, it is also a bit less absorbent as it has ben compressed to a harder surface. ‘Not’ (also called cold pressed) has a medium textured surface and is the most popular finish, it is especially good for beginners. ‘Rough’ is highly textured paper and is the most absorbent. Botanical artists often prefer hot pressed paper as the smoothness allows them to be very accurate in their rendering.
The weights of the papers range from 90 lb to 400 lb. The heavier the weight of the watercolour paper the less the paper will buckle when wet. For lighter weight papers (140lb and below) the paper is usually stretched (wetted and laid out on a board and taped down with gum-strip tape, or you can use a specially designed paper stretcher device like the Keba Artmate).
Watercolour papers can vary in whiteness from bright white to a creamy off-white and are available in tinted colours.
Watercolour papers come in sheets, pads, rolls, and blocks. Blocks are pads of pre-stretched paper that are glued on all four sides except for a small space on one side. This allows for painting without stretching and when the painting is dry you can remove the top painted sheet by running a butter knife around the edge from the gap in the side.

Drawing Papers
Cartridge paper is a high quality type of heavy paper used for illustration and drawing. It comes in a variety of smooth textures. It is available in loose sheets, pads (glued or spiral), hardbound and softbound sketchbooks and rolls.
Bristol paper is a strong and durable, all-purpose drawing paper. It has a very hard surface that is heavily sized, polished, and compressed. It is also used for airbrushing.
Other papers that are suitable for drawing include the very popular Stonehenge paper.

Pastel Papers
Pastel paper is used for soft and hard pastels and charcoal. It is usually coloured paper, with the colour chosen being very important as it will be a major component of the finished work. It comes in a few different textures, all with some amount of tooth or weave that will catch hold of the pastel particles. Ingres is a laid paper with a mesh imprint from a screen. Random texture gets its surface from a cloth matt imprint, similar to Not texture watercolour paper. There are a few types with toothy textures from ground cork or sand that are similar to sandpaper. A few come with the colour screenprinted on and some are waterproof for working the pastels with water.
Paper for oil pastels is hard and white and usually comes in a pad with glassine paper interleaving to protect it from smudging.

Oil and Acrylic Painting Papers
These medium to heavyweight papers are usually canvas textured and primed for painting with either oil or acrylic. Most of the papers prepared for acrylic paint are universally primed to accept both oil and acrylic. Paper must be sealed completely if painting with oil paints because the oil will separate out if the paper is absorbent and form a halo of oil around the colours and it will also rot the paper over time. Although acrylic paint can be used on any paper, acrylic painting paper is usually designed to mimic canvas or it is very heavyweight. Oil and acrylic painting papers are especially useful for taking to classes or using in the field and are an economical choice for making a study or sketch prior to the major work on canvas.
You can also get sheets of primed actual canvas (as opposed to the canvas-textured paper) in pads.

Fine Art Digital Papers
Inkjet papers that allow high quality reproductions of your artwork or prints of your digitally designed original prints come in a wide variety of textures and weights. They are coated to accept inkjet inks. They can be sprayed with an inkjet fixative to prevent smudging if that is a problem. They are archival. Sheets of primed canvas designed to go through your inkjet printer are also available.

For preparing canvas and panels the usual method is to soak the pellets or powder overnight, the next day heat in a double boiler and brush onto the canvas while still warm. Two coats are preferred to seal the canvas well, the first being scrubbed into the canvas to get well into the weave. Discard any left over as it does not re-heat well. Then prime the surface as normal.

Also see Gesso ]]> http://blog.jacksonsart.co.uk/2009/09/01/rabbit-skin-glue/feed/ 0 http://blog.jacksonsart.co.uk/2009/09/01/panel/ http://blog.jacksonsart.co.uk/2009/09/01/panel/#comments Tue, 01 Sep 2009 21:59:59 +0000 Julie http://blog.jacksonsart.co.uk/?p=306 Panel
A rigid surface used for painting.
Usually wood, may be plywood or solid wood. They are often braced to prevent warping both during the priming and painting period and over time.
May also be wood with canvas or paper adhered to the front.

Its use for artists is primarily as an ingredient in genuine gesso and acrylic primer.

It is also the opacifier that makes gouache an opaque form of watercolour paint. It is used in some soft and hard pastels. It is used as a filler for some paints. It is used to enhance the brightness of some paint colours, viridian for example. It is the inert base onto which lake pigments are precipitated. Some forms are used in modelling paste in acrylics and mixing with oil makes oil painting putty.

It is not strong enough to be used as a white pigment.
It is added to paper pulp as a buffer, to counteract reactions with pollution that would cause acidity in paper.
It is also used as a polishing powder and in ceramics as a flux.

Acrylic primer (less correctly called acrylic gesso) is an example of a ground that is also a size. It does both jobs, sealing the substrate and providing a good surface on which to paint oils or acrylics.
Genuine gesso is a painting ground for oil paint and egg tempera in particular, but any paint can be used on it.
An oil ground is oil paint painted on top of a sizing over the entire surface to prepare the surface for painting with oil colours. So using an oil primer means you cannot paint on that ground with acrylics as the ground will repel the paint.

See also Gesso and Primer

Painting with soft pastels requires a ground with a tooth to pick up and hold the pigment particles. This toothy pastel ground can be painted onto paper, canvas or panels, or surfaces can be purchased with the ground already applied to them.

To create an absorbant paper-like surface on canvas or panels for painting with watercolours, Absorbant Ground can be used. It is painted onto sized or primed canvas or panels. It is the ground, not the size and the substrate must be sealed first.

Gesso is made with calcium carbonate (also called whiting, chalk and gypsum) in a binder. It is painted on the canvas, paper or wood panel surface to create a ground on which to paint. Sometimes white pigment (usually titanium, sometimes zinc) is added to make the gesso very white.

Genuine gesso (also called true gesso) uses animal skin glue (hide glue or rabbit skin glue also called “size”) as the binder and the artist often makes the gesso him/herself, using a double boiler to melt the glue powder and adding the whiting. Rabbit skin glue is now also available ready made and just needs to be warmed.
One recipe for traditional gesso: 3 parts size, 1 part chalk, 1 part pigment powder. It is a rather lengthy, messy, smelly process of soaking, heating in a double boiler and mixing.
“Acrylic gesso” is more correctly called “acrylic primer” and should not really be called gesso. It uses an acrylic polymer as the binder for the chalky powder. It is made up of upwards of 14 ingredients. You can also buy ready-made black acrylic primer.

Genuine gesso is less flexible than the “acrylic gesso” and is usually painted on a non-flexible surface such as a wood panel rather than on stretched canvas, so that it will not crack. For paints that need an especially porous surface, like egg tempera, genuine gesso is usually preferred to the acrylic gesso/primer.

The acrylic primer varies a lot in quality and poor quality products can provide a less absorbent ground than is often preferred. Good quality acrylic primer is a very good product for oil painting and acrylic painting. It does both steps of the surface preparation in one- it both sizes (seals) the surface and gives a ground for painting. It can also vary in absorbency, with some products called “acrylic gesso” rather than “acrylic primer” being more absorbent and chalky and particularly suited to applications which require an absorbent surface.

Roberson's Acrylic Primer

Acrylic primer differs in thickness, opacity and grittiness of surface texture, depending on the manufacturer. It is usually too thick to use straight out of the bucket and should be diluted with water until it is the consistency of heavy cream. Most primers have instructions that advise you apply three thin coats rather than one thick coat. A very thick coat may crack as it dries. The first coat is often scrubbed into the weave of the raw canvas in circular motions to be sure that it is well sealed. The first coat will soak into the canvas or panel and act as its own sizing (sealer). Then subsequent coats are applied in alternating directions across the canvas. To get a very smooth surface you may wish to sand with sandpaper between coats. Some acrylic gessos are designed to have a harder surface specifically so they may be sanded smooth, but as they are less flexible they may crack on a movable surface such as stretched canvas, so should only be used on rigid surfaces.

For oil painting it is especially important that the oil never reaches the substrate as it will rot the canvas, paper or wood. Traditionally oil painters seal the surface with rabbit skin glue and then prime the surface with gesso (glue with chalk). Using these two layers assures that none of the oil will seep through. Some artists who use ready-made stretched canvases will apply an additional layer of acrylic primer to the surface to ensure that it is well sealed.

For painting on paper you may wish to prime both sides of the paper (one after the other dries) as the paper will curl when it is wetted by the primer. Painting the other side then un-curls it. For oil paint on paper you may want at least three coats.

Priming your painting surface is part of properly creating a painting. The underlying structure is very important to the longevity of the painting as well as to the appearance. Primer creates a surface that is sealed just enough to prevent the paint seeping through to the substrate (canvas, paper, wood), but is absorbent enough to hold onto the paint. If you were to paint on an unusual surface like a rubber toy, the paint might not adhere properly. But if you prime the surface with acrylic gesso/primer first, then your paint will go on properly and stay on. The primer is stickier than paint and will glue the chalk to your substrate and create a better surface to paint on.

While the gesso/primer is wet it may leach colour up from the substrate and cause discoloration to the whiteness of the gesso. The glues in plywood, the resins in wood panels and in stretcher bars may be water-extractable. Sealing the wood or canvas first with a sealant medium such as Golden Acrylic’s GAC 100 will prevent Support Induced Discoloration (SID). Sealing (sizing) with rabbit skin glue does the same thing if you are using genuine gesso. Then prime as normal.

Some artists prefer that the substrate shows through underneath the paint and so they use a clear primer. This is usually an acrylic matte medium. This is a thick white liquid that dries clear so you can see the canvas. The texture is very different to gesso since it does not have the chalk powder in it, the surface is smooth and not as absorbent.

Be warned that priming can be a messy business. Gesso/acrylic primer dries quickly on brushes and can stain clothes. Be sure to use drop cloths and wash everything as soon as possible.

Many artists use the word gesso as a verb meaning “to prime” as in “I will be spending the day gessoing canvases in the studio”.

Some artists mix gesso in with their paint as a painting material.