TIPS AND TECHNIQUES

Mixed media is a term that can throw even the staunchest of the conservators into a cold sweat.  Restorers will tell you they spend much of their time giving emergency-room care to paintings that are in some cases younger than they are.  What happened?  Well, the answer was that with art moving away from traditional materials and methods, artists in the spirit of free expression neglected to follow rules that had served their predecessors so well.  They introduced materials that we designed for decorative or industrial purposes and mixed materials with abandon.  They were not aware of the limitations of their materials.  Here are a few guidelines to consider when working with mixed media.

The first part of creating a work of art is the support.  The choice of support is critical as it forms the foundation on which your work of art will be built.  There has been an increased use of nontraditional supports in the past few years.  Artists have discovered Mylar, silicon rubber, plastic, natural and synthetic fiber, fiberglass, metals, etc.  The permanence of some of these materials is still unknown.  The effect of time, light, humidity and temperature on surfaces such as Mylar or vinyl is questionable and only time will tell.  Materials developed for commercial applications are designed for a specific purpose and usually permanence isn't high on the list.  Remember we live in a disposable society!

Traditional supports for oil painting are canvas and panel, but oil can be used on acid-free paper or board if it is properly prepared.  If the surface isn't protected however, the linseed oil will leach into the support and in time it will deteriorate.  To adhere properly, oil paint requires a surface that has tooth and absorbency.  Protecting the surface with shellac, fixative, acrylic varnish or acrylic paint will protect the paper but will not provide a sympathetic ground.  Norman Rockwell prepared many of his illustration boards with shellac before painting with oil in the 1920s.  Now many of these paintings are in poor condition after only 80 years - a short time in the life of a painting.  When you paint on illustration board or paper, acrylic white or clear gesso will provide a permanent protective surface.  If you apply white gesso in thin coats, the texture of the surface, will be preserved, and the same is true of the colour if you use clear gesso.

Artists continue to mix oil and acrylic in a painting.  The bad new is that the old phrase "oil and water don't mix" is true and mixing these materials can cause problems.  They can't be mixed together when wet, nor should they be layered over each other in a painting.  Oil and acrylic have different expansion and contraction rates.  Acrylic always remains flexible, and is hydroscopic, and will swell when the humidity is high.  Oil paint on the other hand becomes brittle with age.  So what you are constructing is a moving foundation under an increasingly fragile layer of oil paint.  This will probably cause cracking of the oil paint with time.  Acrylic paint has very little tooth and is not absorbent so it can't allow the oil paint to bond properly.  Acrylic painted over the oil is an even worse situation; it not only keeps the oil from curing properly but also the acrylic will not bond properly to the surface of the oil paint and will separate.  Oil paint takes along time to cure so these problems often don't occur for several years; this unfortunately tends to lull painters into a false sense of security.  Acrylic gesso is formulated to provide a stable, absorbent ground for oil or acrylic painting.  A word of caution though, many of the acrylic gesso sold today are of a poor quality, so take care when selecting one.  A good guideline is to purchase one made by an established art materials manufacturer.  Never economize on your primer, it is the foundation for everything that follows.  If it fails, it doesn't matter how good the rest of your materials are.

I was asked at a college seminar, "Since acrylic and water-mixable oils dissolve in water, are they inter mixable? the answer is no!"  Water-mixable oils have been designed to break down in water but are still oil paint and subject to all the rules that apply to traditional oil paint.  Most water-based materials however do work well together.  Watercolour and gouache share the same binder, gum arabic, so they mix without any problem.  Pastels can be applied over watercolour and then blended with water if you wish, as their binder, gum tragacanth, dissolves in water and mixes with gum arabic.  Care however should be taken that the paint layer is kept thin, as both gun arabic and gum tragacanth will crack if applied in thick applications.  Painting over watercolour with acrylic paint or inks shouldn't cause a problem because of the adhesive strength of the acrylic binder.  However if the process is reversed and watercolour, gouache or non acrylic based inks are painted over an acrylic underpainting, they will very likely crack and separate as the gum arabic or shellac will not form a stable bond with the acrylic.  You can safely use acrylic based inks like FW or liquid acrylics over an acrylic painting as they share a similar binder.