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Braced/Cradled Panels

Surface checking on gessoed plywood
Surface checking on gessoed plywood.
Support Induced Discoloration
Wood panel on left has not been sealed prior to applying gesso, exhibiting Support Induced Discoloration. Panel on right has a sealing layer prior to applying final gesso layer.

In order to give a panel extra support, bracing or "cradling" is often used. Today's artists are fortunate in that manufactured panels are dimensionally stable enough to be cradled or braced. However, much more research must be done on this subject as more wood panels, many of which are imported, are exhibiting structural issues such as warping and bowing. These panels are typically made with thin 3 mm plywood and braced with solid wood strips. While aesthetically these panels are very appealing, there may be an inherent imbalance in the construction of these panels, especially larger ones. Thinner plywood tends to warp and when braced with a solid wood strip, there will be a tendency for any warp in the plywood to force a change in the solid wood strip and vice versa as the panel is exposed to humidity changes. As discussed earlier in this article, solid wood strips still have their original cell structure and are more susceptible to dimensional change as the relative humidity of the air changes. In Ampersand Art's extensive experience manufacturing cradled panels, we have seen that bracing large panels with high quality plywood will give you the best protection against warping. Ampersand Art uses a 13-ply plywood for bracing their museum panels over solid wood strips due to the stability of the plywood. The dimensional stability of a 13 ply birch plywood provides a much more dimensionally stable strip of wood, which is less prone to warping. Additionally, do not nail or screw the cradle onto the panel, or you will affect the painting surface over time. With wood expansion and contraction, nails will come loose over time. Use professional grade wood glues to adhere the panel to the bracing system.

Sealing And Priming

With the exception of encaustic wax which acts as a sealer, all wood panels should be sealed with a good primer before painting artwork on them. Lignins and tannins that naturally exist in the wood can actually leach through the ground and affect a painting if a panel is not properly sealed and primed. The image (left) demonstrates how a panel without a sealer will yellow while a sealed panel will block the tannins from leaching through to the painting ground.

There are several recommended methods and resources to learn about sealing and priming a panel. The updated Painter's Handbook by Mark Gottsegen is an excellent resource. Ampersand Art Supply also has a section on their website for sealing and priming unfinished panels. Ampersand recommends using GOLDEN GAC 100 to seal panels followed by several layers of gesso or an acrylic dispersion. Gamblin Oil Painting Ground can also be used to seal and finish a panel prior to painting with oils.

Prepared/Ready To Use Panels

While it is not the intent of this article to evaluate primed artist wood panels that are available to artists on the market, the information in this article can be used to evaluate the construction of the wood panel itself. Over the last 20 years Ampersand has developed a process for sealing wood, specifically hardboard for its museum series panels and high density boards used for its value series panels. Prior to coating the panels with the actual painting ground (i.e. Gessobord™, Claybord™ grounds), Ampersand primes the wood substrate in a two part process with a tannin blocking sealer/coating system specifically developed to eliminate support induced discoloration in an artwork. The first "fill coat" serves to seep into the top fibers of the hardboard to begin the first part of the sealing process. This fill coat is applied with a precision roll coater that ensures penetration of the coating into the fiber of the board and creates a good bond between the board and the sealer. The second coating completes the sealing process and provides a good adhesion layer for the different painting grounds that are applied to the sealer coat. Again, sealing wood is essential and should be a practice followed by artists preparing their own panels or any manufacturer creating prepared panels for artists to create their works of art.

References/Sources

  • The Painter's Handbook: Revised and Expanded - Mark David Gottsegen, Copyright, 2006
  • The Encyclopedia of Wood, USDA, Copyright 2007
  • Today's Hardboard, AHA, Copyright 2001
  • Dimensional Stability, CPA technical bulletin, Copyright 2002
  • MDF From Start to Finish, CPA Copyright 2005
  • Hardboard (Masonite) What is it, RM Granum and O.B. Eustis, PPI, Copyright 1999
  • Wood-based Composites and Panel Products by John A. Youngquist (source: Wood Handbook: wood as an engineering material - chapter 10) Forest Products, Madison, WI copyright 1999
  • Industry websites used to gather technical specifications on various brands of panels
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