Conservation Care and
Framing of Oil Paintings 

1. Oil paintings should be oiled up until the painting stops sinking.
   
    
2. Paintings should have a final varnished when dry, 3-6 months depending on thickness of paint. (Some restorers believe with modern cleaners that this is not required.  We still recommend vanishing since it will reduce damage to the paint surface during minor household cleaning and chemicals in the environment.)
    
3. Oil paintings should be varnished before they are 12 months old.
    
4. Type of varnish, manufacture, & medium used should be identified on the canvas overlap, back of the stretcher bars, or back of the panel.
    
5. PH neutral rabbet tape should be used to protect the painting in the frame rabbet.
    
6. Stretchers should not be nailed to the frame
    
7. Painting should be secured to the frame by using canvas off set clips or iron mending strips.
    
8. A protective backing should be secured to the back of the stretchers.
    
9. Air circulation holes should not be cut in the protective backing
   
    
10. Bumpers should be placed on the back of frames to create a space between the back of the painting and the wall for increased air circulation.
     
11. Backs of the canvas should not be written on.
     

Rabbet Tape

Rabbet tape is a PH neutral nonporous tape that is placed in the rabbet of a frame in order to protect an oil painting from the acid in the frame.  Even if the painting is totally dry (3-6 months for oils) the painting can adhere to the frame.  This can cause damage to the painting (removing paint) if the painting has to be removed from the frame.  Discoloring of the edges of the painting can result from chemical reaction of the paint with the framing material. Using rabbet tape in the frame rabbet will help protect the oil painting from these potential damages.

Backing Board

The back of a painting should be protected by fastening a backing board to the back of the stretchers.  The backing board will create an insulation chamber, reducing the effects of sudden temperature and humidity changes.  Sudden changes in temperature and humidity can damage the painting and will become evident over time.  Also, it protects against punctures and blows from the rear, along with accumulation of excess amounts of dust along with minimizing small things from becoming wedged between the canvas and the bottom of the stretchers. Fome-cor should not be used as a backing board for long periods of time (less than six months) due to the harmful chemicals it gives off as it deteriorates.

Backing board will reduce damage caused by moving and handling.  The backing board will reduce the movement of the canvas when the canvas is moved, reducing stain and potential damage.  Even if the damage is not noticed after handling does not mean that it has not occurred it only means that the damage has not reached the outer surface layer, yet.

The backing board should be attached to and cover the stretchers/strainers and not be attached to the frame.  Screws and washers are recommended by some conservators while others recommend archival gum adhesives.  There is uniform agreement that backing boards should be used.  The only question one might ask is if circulation holes should be cut in the backing board to reduce mold and potential dry rote of the canvas.  The vast overwhelming majority of data to date indicates that circulation holes should not be cut in the backing board.  American Institute of Conservation of Historical and Artistic Works (AIC), the National Trust, Stanford University, Getty Museum, most conservators and others agree that backing boards should be used and that holes should not be cut in the backing board.

Cutting holes in the backing board results in more rapid environmental changes directly opposite the holes.  Resulting in significant increased strain and localized cracking inevitably will occur opposite the holes.  Circulation holes have been proposed in the past as a method to reduce dry rot and or mold formation.  However even with circulation holes mold will form unless the relative humidity is kept below 65% (mold formation threshold).  The best way to prevent mold is to maintain an environment for the painting with the relative humidity less than 65%.  Since cracking will occur if holes are cut in the backing board and mold formation is not prevented holes should not be cut the backing board.  Mold formation is more prevalent with acrylics than oils but remains a problem for both.

Bumpers should be used behind paintings to allow air circulation.  This will help stabilize the temperature and relative humidity on the painting.  Mold formation will be reduced if the relative humidity is generally less than 65%.

Backing boards should be archival PH neutral or slightly basic (PH>7.0) matt or artist board heavy enough to reduce the risk of punctures.  The natural Trust recommended Melinex 125 at the conclusion of their 1993 research into backing material for interior walls with relative humidity less than 65%.  The Trust is continuing this research effort for backing material for exterior walls.  At this time we have not been able to locate this information.

Fastening the Painting to the Frame

Paintings should be secured to the frame by using canvas off set clips or iron mending strips.  The stretcher strips should not be nailed to the frame for conservation framing.  Frequently the frame or stretchers can become damaged when the painting needs to be removed.  Nailing the stretchers to the frame prevents the painting from expanding and contracting with changes in temperature and can damage the painting.  In addition to much pressure can be placed on the painting against the rabbet of the frame.  This can case the painting to adhere to the frame, particularly when rabbet tape is not used, damaging the paint when it is removed from the frame.

Writing on Back of Canvas

The information should not be written on the back of the canvas.  The pressure of the writing instrument will put stresses on the painting which will eventually appear on the front of the painting.  Also chemicals in the ink can have an effect on sizing and ground reducing the ability of the paint to stay attached to the canvas.

Care of Acrylic Paintings

Artist Acrylic Paints were introduced in the 1950’s and have become popular with many artists.  Acrylic paints are different from traditional oil paints in their chemical and physical properties.  Some traditional conservation methods can be harmful to an acrylic painting.  Acrylic paintings like pastels require special handling.  With proper care they should last hundreds of years.

1. Paintings should have a final varnished when dry.
     
2. Type of varnish, manufacture, brand of acrylic & medium used should be identified on the canvas overlap, back of the stretcher bars, or back of the panel.
    
3. PH neutral rabbet tape should be used to protect the painting in the frame rabbet.
    
4. Stretchers should not be nailed to the frame
    
5. Painting should be secured to the frame by using canvas off set clips or iron mending strips.
    
6. A protective backing should be secured to the back of the stretchers.
    
7. Air circulation holes should not be cut in the protective backing
   
    
8. Bumpers should be placed on the back of frames to create a space between the back of the painting and the wall for increased air circulation.
    
9. Backs of the canvas should not be written on.

Varnishing Acrylic Paintings

Behavior and properties of Acrylic Paint

• Dry in 30 minutes versus 48 hours to the touch for oils
• Acrylic paint is more flexible than oil and will develop fewer cracks than oils.
• Acrylic films are not as hard as oil films.  The surface is soft and holds onto dust and dirt.
• Over time the soft acrylic film can flow around dirt particles incorporating them into the paint film.
• A variety of additives are added to the acrylic paint.  These additives vary between manufactures.  Because the additives differ between manufacturers so will the properties of the acrylic paint film.
• Some of these additives are solvent soluble while others are water soluble.  Some water soluble additives remain water soluble after the acrylic has dried causing cleaning problems.
• Some acrylic paintings may appear to form a gray veil on their surface or develop yellow discoloration with aging.
• When exposed to sub-zero temperatures the become more brittle and will crack.

Cleaning Concerns

Acrylic paintings attract and gather dust easily.  Acrylic emulsion paints used in the fine arts have a glass-transition temperature (Tg) near or below room temperature.  Thus at room temperature the surface will be soft and will hold dust.  Dirt can become part of the paint film.  Acrylic resins are non conductors and will hold an electrostatic charge which attracts dust.

Cleaning an acrylic emulsion with water may remove water-soluble additives and could affect the pigment/polymer binder causing colors to appear less saturated.  Cleaning can also cause the thickener additives to swell.

Heat Sensitivity

Acrylic paint becomes very soft around 140^o F.  Temperatures above this are required in conservation to apply a lining of fabric for repair.  If the fabric that the acrylic is painted on becomes damaged it may not be able to be repaired without altering the artist’s unique brush strokes.

Pressure Sensitivity

The acrylic film is soft at room temperature and dents easily with just fingernail pressure.

Mold Growth

Mold growth has been noted on acrylic paintings and has become an increasing concern among artists and collectors.  There is no ideal treatment that does not cause some degree of damage to the painting.  As temperature and humidity increase mold growth becomes more apparent.  The best cure for mold is prevention.

Storage

Acrylic paintings should be stored in a dust free environment to prevent dirt from becoming part of the paint film.  Also they should be stored below normal room temperature to prevent further softening of the paint film.

©  1999-2006 PJ's Studio
All artwork Copywriter and cannot be reproduced or otherwise
utilized without written permission from the artist
432-683-9330  pj@peggyflanders.com