Painting Supports - Part 2
Updated: Nov 13, 2022
In part one I discussed the benefits of solid panel supports and how they outperformed stretched canvas in every way except weight. Unfortunately, large panels are very heavy. For small to medium size pictures, solid support provides the balance between longevity and ease of use.
Summary: Preparing your own engineered wood supports from scratch can be fulfilling if you have the tools, patience, and skills to do so. However, using already cut panels can provide a way to make high-quality supports that are outstanding. Hardboard and cabinet-grade plywood are excellent supports for paintings.
Wood Panel Types:
Let’s deal with only two major types of solid painting supports, despite the existence of many others. Good artist-made supports can be created using either high-quality cabinet-grade plywood such as birch veneer or hardboard. For artists considering making their own supports, the most economical way to go about this is to purchase 4 x 8-foot stock. An adequate thickness for plywood is one-quarter of an inch. Undressed hardboard also comes in 4 x 8-foot panels at 1/8 inches in thickness from hardware distributors and in smaller, standard painting sizes if it is purchased from an art materials supplier.
Cutting Panels Into Suitable Sizes:
If you are confident in your woodworking skills you can cut large 4 x 8-foot sheet goods into standard-size painting panels, or for a fee, some hardware stores may offer to cut large panels into smaller sizes for you. Artists who are intimidated by table saws (and don’t be fearful to admit it) have found it easier to use a circular saw along with a high-quality straightedge guide to cut large sheets of plywood or hardboard.
It takes planning and equipment like clamps, sacrificial boards, and sawhorses to cut large boards safely and accurately with a circular saw using a straightedge guide. Plywood can be a bit easier to handle when the panel is large since it is more rigid than large sheets of hardboard. Large-size hardboard is very flexible. A strategy you are comfortable with needs to be devised to keep hardboard flat during the cutting process.
Use caution and select a method that fits your skill and equipment inventory Power tools are extremely dangerous and must be treated with an overriding dose of respect. Take this from someone who was hit in the head by a two-inch by 3-inch piece of poplar kicked back at me by a table saw. I was not harmed, but the incident was lightning fast and frightening. It was a hard way to obtain a valuable learning experience in how the rear part of any table saw blade can eject wood that binds and fails to pass parallel to the rear of the spinning blade. I use a variety of safety tools now to lessen the possibility that wood does not become a high-speed projectile.
Remember you can bypass cutting wood by purchasing already cut panels that you can prepare with your own sealer, primer, or canvas adhered to the panel.
Sealing the Panel:
Now starts the far less perilous part of panel preparation. The first step is to apply 3 coats of solvent-based polyurethane to the panels. This will seal the wood to stop moisture from penetrating it. In addition, polyurethane helps to inhibit the migration of acids inherent in wood, especially if you plan to glue canvas to a panel.
Important: If you intend to apply acrylic primer on the side of the panel that you will use for your artwork, you have 2 choices. 1. Do not apply polyurethane to the side that you will be priming with acrylic gesso. Apply 3 coats of polyurethane to the back side and edges. Then apply acrylic primer to the uncoated wood side that will be used for your painting. 2. Go ahead and apply 3 coats of polyurethane to all parts of the panel. Select the side that will be for your artwork then sand that side to roughen the polyurethane. Next, apply a bonding primer so that your acrylic gesso will adhere properly to the panel. Bonding primers such as Zinsser B-I-N or Insl-X are examples of primers of this type. After the primer dries completely (follow manufacturer's directions) you are ready to apply 2 or 3 coats of acrylic gesso or an oil primer if you so desire.
Use a small brush, mini-sponge roller, or other appropriate paint applicator and seal all the surfaces, especially the edges with polyurethane. While the polyurethane is drying you can use the time to prepare canvas that will be glued to the panels if you wish to paint on a canvas-textured surface.
Painting Surface Selection:
This is another point where a decision needs to be made. Selecting canvas is a personal choice. You may also choose an unprimed or pre-primed canvas. Either one will work well in making solid painting supports.
Adhering Canvas to a Panel:
The types of adhesives available for this application are limited. In most cases, the simpler the better rule should be observed. Artists have used the following adhesives with success: Polyvinyl acetate glue, (Elmer’s type white glues) aliphatic resin emulsions, (Titebond) acrylic dispersion mediums (acrylic matt or gloss mediums, acrylic gels), and thermal setting adhesives. (ethylene vinyl acetate) The first three are the easiest to obtain and apply and are compatible with sizing and ground layers that will be applied after the canvas has adhered to a panel.
First, sand the surface of the polyurethane coating on the side that will have canvas glued to it. That helps the glue adhere to the polyurethane.
The glue can be applied with a brush to coat the entire surface with a generous film. Some artists employ floor tile adhesive applicators with a fine saw tooth pattern to create a striated but even glue coating. After the glue is applied, place a piece of canvas cut slightly larger than the edge of the panel. The canvas will shrink a bit and this overage will assure that the entire panel is covered. You can trim the excess canvas when the panel is dry. Use your hands to smooth out the canvas followed by using a hard rubber roller to assure an even bond between the panel and the canvas is maintained. Look for bubbles on the surface and push them out to the edge of the panel.
Gluing Canvas to Panels:
When I have fabricated solid painting panels, I do this as a batch process. I will make many of them in one session. Making multiple panels helps with the gluing process by stacking them atop each other to help assure that the panels remain flat, and the canvas makes even contact with the panel. Stack them and interleave sheets of wax paper between each panel to stop them from sticking together if any stray glue oozes out and gets on the surface of the canvas. Also, weigh the stack down with heavy objects to press the panels and mitigate any tendency of the panels to warp because of the moisture introduced by the water-based glue. Good sources of weight for your stack of panels are old art history books or any college science textbooks. In some cases, textbooks you never opened can finally come in handy.
Inspect the dried canvas and trim any excess fabric before proceeding to the ground application stage. If air bubbles or voids are created where the glue dried before the canvas made firm contact with it, you can remedy this in two ways. First, if it is near the edge, you can peel up the canvas, apply glue with a brush and then apply pressure to adhere the canvas to the panel. The second way is to use a household iron for pressing clothing. Set it to medium/high heat. Place a sheet of plain white paper on top of the canvas where the defect is and run the iron lightly and repeatedly over the top of the paper. Make very quick, firm passes over the problem area. The trick is that you do not want to overheat the glue. Many adhesives break down at high temperatures.
I have not attempted this fix with a pre-primed acrylic canvas and fear that heat applied to an acrylic dispersion coating will melt and stick to your iron. Your significant other will really “appreciate” an iron streaked with a hardened acrylic primer on it the next time they use it to press a garment. Art production should not get in the way of domestic tranquility. Buy an inexpensive iron exclusively for dealing with panel preparation issues. It could save your relationship.
Glue problems are somewhat easy to repair because, during the first few hours, the glue bond is fairly weak. It is easy to pull the canvas away from the panel within a short period after applying the glue. When experimenting with acrylic gels I have noted that as the acrylic gel ages, the adhesion appears to become stronger. That is why you need to inspect the panels within an hour of gluing them. It is the best opportunity to assure a successful repair.
Disassemble the weighted stack of panels and allow the water in the glue to work its way out of the canvas. After several days, proceed to the final step of applying the ground coatings of your choice. If you use pre-primed canvas, you are ready to use the panels.
In preparation for creating a finished surface for paint application, assure that the canvas is free of moisture from the adhesive if you intend to apply an oil ground. It is not as critical if you are applying water-based ground. Follow the directions provided by the manufacturer for the application of the oil ground you select.
Sizing is a debatable issue when using acrylic dispersion grounds and the painting will be executed in acrylic paints. However, if any unsized or unprimed fabric is left exposed to air, the cloth will weaken due to oxidation, and it will also change color from dirt that adheres to the surface.
For artists painting directly on a prepared hardboard or plywood panel, sizing is not needed IF you coated the wood with several layers of gloss polyurethane varnish. If you “refrain” from applying polyurethane to a raw plywood or hardwood panel, sizing is needed to seal the wood so that Support Induced Discoloration (SID) does not make your priming layer and paint take on a light beige appearance. SID is triggered when water-soluble components in wood are drawn to the surface by an acrylic primer.
If you choose to paint directly on the polyurethane surface without additional priming, rubbing the surface with a steel wool pad or sandpaper will provide sufficient tooth for paint to adhere to the surface of a polyurethane-varnished panel.
For panels with canvas adhered to them that will receive an oil ground primer, sizing of the canvas is important because any oil from the ground mixture that encounters canvas unprotected by the sizing will oxidize rapidly and deteriorate. Follow the recommendation found on the size you select and after applying it, let it dry completely before proceeding to the application of the ground. Oil grounds applied directly to a polyurethane varnished panel are ready to be used once the oil ground has dried completely. You may wish to test your oil ground to assure that it adheres adequately to polyurethane.
Acrylic Grounds on Canvas:
Select the best acrylic dispersion primer that you can afford. Avoid primers that are as thin as milk. They don’t have the acrylic solids or pigment necessary to provide a good stable base for painting. Conversely, avoid the extremely thick primers that require you to use a palette knife to apply the material. Extremely heavy-bodied primer may contain too much filler and not enough acrylic polymer to sufficiently protect a canvas that is used as the surface adhered to a panel. Super thick primers might be filled with an abundance of calcium carbonate that will absorb too much oil from the initial paint layer and cause potential delamination of the paint as it ages.
Follow the instructions provided by the manufacturer as to the application method and number of coats. In many cases, 3 coats will be the minimum amount needed. Don’t skimp on this process. This is not the time to be cheap. If the primer says do not dilute it, heed this warning. Under bound primer is an accident waiting to happen.
Professional commercial painters do not recommend that acrylic paints be applied directly to polyurethane without preparation. Sanding to de-gloss and application of a bonding primer is needed for acrylic gesso to bond to polyurethane. (See the paragraph above that starts with "Important" in red text.)
I repeat that polyurethane needs to be sanded and then primed with a bonding primer to provide sufficient adhesion of an acrylic primer. If adhesion is poor, coat panels with polyurethane on the back and edges and leave the face alone. Apply several generous coats of acrylic primer to the remaining non-polyurethane-covered surface. The primer and subsequent paint will act to slow moisture penetration to some extent.
You made it to the end of this Syntax essay and it probably took longer to read this text than it will take to create a panel for painting. However, if you persisted, obtained the materials, cut the panels, did not need a visit to an Emergency Department to address any accidents, and finished preparing the panels, you are now in possession of several solid-support painting panels that have lots of wonderful working properties. I realize that making your own panels is not for everyone. But knowing how to do so can be helpful if you purchase ready-made painting panels and wish to modify them by adding a polyurethane coating to the back of the panel or applying your own primer. This essay should be especially helpful as a guide for those who buy ready-to-prime raw hardboard or plywood and want to turn them into panels that will perform well and last a long time.
If you are brave and create your own panels you now have a painting surface that holds canvas or paint directly on it with little flexing. Your panel cannot be easily deformed by a blow to the surface. You would be hard-pressed to punch a hole in a wood panel. Hardboard and plywood panels don’t take up nearly as much room as a canvas on a stretcher. You can easily secure wood panels within the lid of many plein air paint boxes. Light does not penetrate through wood panels so when you use them outdoors an annoying feature of light transmitting through the stretched canvas on your outdoor easel is eliminated. They transport well. Finally, you know the quality of the materials because you selected them.
Part 3 will focus on the interface of commercial and art materials manufacturing along with an outline of some of my proposed experiments.
The Syntax of Color