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Canvas

Restoration of Works on Canvas

Hopefully, you will never be faced with damage to paintings on canvas--damage that often is severe.  Improper storage and accidental mishap are two of the major causes of damage.  Lack of surface protection, like that provided by glass or acrylic sheeting on watercolors, drawings, etc., allows unexpected damage.  Once the damage occurs, you are faced with some decisions.  Is the value (personal or monetary) of the work high enough to warrant professional restoration?  Is the damage minor, possibly enabling you to repair it yourself?  Where can you go for materials for restoration?

Before any amateur tips or techniques are shared, it should be explained that the only way to restore damage to canvases in a totally archival way is to deliver the damaged artwork to restoration professionals for repair.   They are trained to deal with every aspect of the work, from period paint composition to fabric reconstruction to up-to-the-minute, non-evasive methods.  If you are lucky enough to have a valuable artwork, always consider using a professional restorer.

That said, we will now examine two types of damage most often associated with works on canvas: tears/holes/rips and flaking or scrubbed surfaces.  These two problems can be corrected without extreme amounts of knowledge or training, but only if maintaining the value of the artwork is not a factor.

To repair tears, you will need some basic repair materials before you can begin.  These are now readily available from art supply centers and are manufactured by several companies.  First and most important is an acid-free, archival adhesive, often vegetable based but sometimes synthetic; small pieces of cotton canvas (larger than the tear or rip); brush for adhesive application; brush to remove excess adhesive; books or wood to elevate the back side of the canvas; smooth weights (or books) to apply even pressure to the repaired area; and fingernail scissors.

Rips and tears in painted canvases occur when trauma has occurred to the front or back of the canvas.  Once painted, there is less stretch or give in the fibers of a canvas and the surface becomes somewhat brittle.  But, nevertheless, there is only so much “give” in the surface of fabric to start with.  If an item has been allowed to fall against the front or back of a painting and has caused a rip or two-way tear, there is a simple and widely accepted method of repair.

Apply an acid-free adhesive to a piece of fresh canvas large enough to cover the tear.  Press gently to adhere the canvas to the back of the painting. Carefully turn the painting over. Support from the back side of the painting is essential as you work on the repair.  This support can be a book or small scrap of wood covered with plastic.  The book (or wood) should be the same thickness as the canvas stretcher bars so that it will elevate the painting to the proper height without stretching. Press against the canvas patch you just glued to the back of the painting.  From the front, gently bring the edges together and work any frayed edges of the tear into the soft adhesive.  This can be done with a toothpick or similar tool.  Use a brush or clean cloth to remove excessive adhesive on the surface of the painting.

Place weight over the repair and allow it to dry completely.  Once dry, remove the supports and examine the surface of the canvas.  If there are an inordinate number of threads above the tear, carefully trim with nail scissors.  If they are not trimmed, they will show later.

When the surface is as smooth as possible, apply paint of the same type (oil, acrylic or alkyd) to the affected area.  This should be applied over the tear only, and then gently smoothed into the surrounding area.

Scrubbed areas are much easier to repair.  Paint of the same type (again oil, acrylic or alkyd) should be mixed and applied very sparingly to the areas where damage is noticeable.  Allow the newly painted areas to dry completely and then apply medium to match the sheen of the original painting.

When old paintings are chipping or there are areas of deep cracks in the surface, consider going to a restoration specialist.  If you want to do some minor repair to help correct or stop the damage, here is one idea.  Use painting medium that matches the original paint (oil, acrylic) and carefully work medium beneath any loose areas.  Press lightly to reattach chips and then allow to dry.

Cracking on the surface can be serious.  It usually indicates an improper fit between the paint and the surface onto which it was painted.  Perhaps in the case of an old work, the canvas may not have been properly sized prior to painting.  Use medium to hold any loose areas and work it into the crazing, if possible.  The end result will be a painting that will last for many more years.

Painting as little as possible over the original is always preferred to painting too much.  The less you do to alter the original work, the better.  Work with very fine brushes and set the paint on the surface in the exact areas where damage has occurred.  Restoration is a very involved scientific endeavor that should often be left to the professional.  But, sometimes, we can do a little to help delay professional intervention.  Care is the key word.

How to Stretch Canvas

Stretching your own canvas is fairly easy once you know the procedure and have the proper tools and materials. Note that the canvas referred to below is pre-primed; but you could also use the following procedure with raw canvas and, after it has been stretched, prime it with two coats of acrylic gesso. Please read through all of the instructions first, since certain steps must be prepared for in advance.

First you will need to gather a few tools and materials: canvas pliers, stapler/staples or hammer and tacks, stretcher strips, and canvas. In addition, a T-square is convenient to help you insure that the stretchers are square. Then follow these steps to stretch your canvas:

1. Select the appropriate-sized stretchers for the canvas you want to build. Your art supply store has a variety of pre-cut wooden frame rails (or stretcher bars) that have interlocking mitered edges.
2. Once your stretcher frame is assembled on a flat surface, you should verify that it is square. Do this by taking a tape measure and checking that the diagonal distances from both opposing corners are equidistant. (They almost always will be.) If you encounter an offset, you can correct it by attaching a small metal right-angle brace on the inner frame corner. A small plywood right-angle triangle attached to the rear frame corner will also help correct any shift.
3. For frame rails longer than 36 inches, an interior brace should be inserted between these rails to support them from bowing inward after the canvas has been attached. This will also protect against frame distortion during periods of fluctuating humidity. If this type of support rail did not already come with your pre-cut frame, you should cut a piece of similar wood and attach it with the type of braces detailed in step 2.
4. Take the canvas and lay the primed side down on a clean, flat surface. Place the frame atop the canvas and then cut away any excess material so that there are two inches of excess canvas bordering the frame on all sides. It is important that you leave this border material because this is what you will use to grip, stretch, and attach the canvas to the frame.
5. Fold one side of the canvas over one of the shorter frame rails and then attach a canvas tack at the center of the outside edge of that rail.
6. At the opposite side, use canvas pliers (which are similar to regular pliers except they have a broader gripping area) to grip the canvas at mid-rail. It may be helpful for you to set the frame upright while doing this. With a firm grip, pull the canvas until a straight crease is formed to the tacked end. While keeping tension on the canvas, insert another tack at the center edge of the rail, just like the other side. Note that you may also use a staple gun/staples instead of tacks. (The Arrow JT-21 is easy to use.)
7. Move to the next frame rail (one of the longer ones) and repeat steps 5 and 6. As you do, you will notice a triangular canvas crease as you attach the third side and then a diamond-shaped crease when the fourth tack is attached on the remaining mid-rail.
8. Now, place temporary tacks at all four corners. Starting with the center of one of the long rails, grip the canvas tightly with the pliers and fasten tacks at 2" intervals. Repeat with several tacks in both directions (from center) and then switch to the opposite side and repeat this process. Continue working from the center until both long sides are completely tacked down to all but one inch from each corner, stretching the canvas evenly as you proceed.
9. Once both long sides are finished, remove the temporary tacks that you fastened in step 8. Now repeat the same fastening process for both of the short sides, working out from the centers. For smaller canvases, one entire short side can be fastened first, followed by the opposite side. Larger canvases should be rotated several times to evenly stretch the material over the frame. Note that a primed linen canvas (oil-primed linen, in particular) will normally require that the tacks be placed closer together, due to the limited stretch of this material.
10. Fold and pleat the corners of the canvas and then neatly wrap them around to the rear of the canvas frame. Keeping tension on the material, tack all of the excess cloth to the rear of the frame so that it is neatly secured. Then place tacks on all four outer corners. This excess material is important to have in case you ever need to restretch or remount the canvas.

Any remaining canvas indentations or ripples can be reduced by moistening the affected area with a damp sponge. Be careful not to saturate, and allow the canvas to dry completely in a well-ventilated area.

Keep in mind that it is easier to stretch primed cotton and Polyflax canvas than it is to mount a primed linen canvas, since linen fibers do not stretch as much. Oil-primed canvas requires the most attention when mounting on a frame because it has virtually no stretch. When working with this type of canvas, you may have to remove tacks in wrinkled sections and then restretch and retack.

By following the above steps and using proper materials and a few tools, you can easily build your own canvas. With a little practice, the process becomes much faster and easier, almost to the point of becoming routine.

Canvas Concerns Storing and Shipping

What is the best way to store unprimed canvas? Or primed canvas? How should one store stretched canvas? What is the best way to ship a stretched canvas? How does one preserve and store canvas that has been removed from its stretcher bars? In order to protect this important and essential art material, as well as your finished paintings, read on.

Canvas is a very strong material. Usually made of all cotton, cotton and linen, or linen, it can be woven in any texture from smooth to nubby. Newer synthetic fibers have been introduced as well, and these add strength of a different sort to the basic natural fiber content. Synthetic fibers resist rot and decay far more readily than natural cotton or linen. This quality makes synthetic "canvas" a good candidate for exterior display.

Cotton, linen or synthetic canvas can be purchased either primed (usually with a high quality acrylic primer) or unprimed. Artists who have developed their own formula for underpainting ground or who do not want the surface sealed use the unprimed surface. Many acrylic painters love the near watercolor effects of using unprimed canvas. Both primed and unprimed canvas should be stored away from strong direct light or exposure to moisture. Light will destroy canvas just as it does any form of fabric. Primed is slightly less susceptible to light damage, but UV contact should be limited whenever possible, whether primed or unprimed. Ideally, canvas should be rolled around a firm center and covered to protect the roll from dirt and grime (and UV).

Stretched canvas should be stored standing upright along one edge. Multiples should be stored in such a way as to prevent abrasion of the next canvas. One way to accomplish this is to stack the first two back-to-back, in pairs. Then fronts contact only fronts and backs contact only backs. Standing in some sort of rack can best facilitate this. Storing one on top of the other in a stack will promote warping of the stretcher bars and also creates a situation where objects could fall onto a painting and cause damage or possible rips.

Shipping a stretched canvas requires one of several options to be exercised. First and most chosen is the procedure of wrapping the (dry) painting in soft foam sheeting and then packing in a heavy cardboard carton. Shipping/storage companies offer several choices in heavy corrugated boxes. Choose one that is at least 6" larger on all sides than the painting (including the thickness of the art). Fill all areas around the painting with foam sheets, making sure there is no room for the painting to slip or move during transport.

Crates can be built (either by you or a freight company) for shipping ornate, oversized, or extremely valuable artworks. These crates resemble what you might expect a giant piece of heavy machinery to be shipped in. The sheer size and proportions of the crate make it an expensive option, but one that might be necessary for some works.

Paintings purchased at times when crating is impractical (such as when traveling), can be removed from their stretcher bars for shipping. This makes the size (and the cost) smaller and more manageable. To remove the tacks or staples from the stretcher bars, use a sharp instrument such as the tine of a screwdriver or a pocketknife and a pair of pliers. Gently lift the tack or staple up, and then grip it with pliers. Remove all tacks or staples. Cover the painting with a soft cloth or smooth paper and carefully roll the painting to fit a large, heavy mailing tube. Avoid rolling too tightly. Pad each end of the tube so that the edges will be protected from crushing. It is sometimes possible to reuse the stretcher bars, so they might be collapsed and shipped with the canvas. Ship stretcher bars in a separate package or tube, as they could cause creasing or other damage if shipped inside the tube with the painting.

Rolled, painted canvases should be unrolled and re-stretched as soon as possible. The simple act of rolling a painting, even though the surface is somewhat flexible, could cause cracking or other damage; and the longer it stays rolled, the more likely damage is to occur. If you are unsure how to re-stretch the canvas (and there is a special technique to stretching) consult a professional framer who will be able to re-stretch the work for a nominal fee.

Proper storage of artworks, especially stretched canvases, is vital to their long life. If stretched canvases are exposed to prolonged periods of high humidity (such as a warehouse or garage storage facility that is not air conditioned), severe warping of the stretchers can occur. That is the most immediate and obvious damage. Humidity creeps into the painting and penetrates between the painted surface and the canvas onto which it is painted. Cracks and crazing are the end result. When examined closely, these cracks (caused by excessive humidity) go all the way through the painting, right to the canvas core. It may take many months for the extent of the damage to become visible, but by that time the damage is already done. Correction can be made by a conservator, but at a very high cost.

As you can see, by taking just a few simple precautions in the storage and shipment of canvases, you can save yourself lots of time, disappointment and money.