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All Things Ampersand

Panel Edges

Recently, we had a question about SID effecting the paint on the panel edges.  An artist was concerned about paint on the edges of the untreated panel, not cradle, and how that might effect his work long term.  Below, Dana Brown answers the question.


“The condition of SID is one of acrylic paint and acrylic dispersion ground (acrylic gesso). We make broad recommendations to sealing the painting surfaces of wood, as a separate step from priming, primarily due to the common use of acrylic gesso as a primer, but also to maintain a painting surface that is as acid-free as possible. It is also based on an understanding that proper habits can become good practice when using various materials. We know that sometimes artists will pick up a piece of wood to use as a substrate, not knowing its density or acid-level, and sealing the panel will give the painting a ‘fighting chance,’ of lasting.


Because of the differing characteristics of each paint type mentioned, I will address each separately.

Acrylics dripped over the edge (that thin, 1/8” thickness) will encounter some level of acids. It will also take on a level of discoloration. Support Induced Discoloration (SID) is not a dark blackening or even a dark browning of the paint film, and it is generally only noticeable in areas of white and generally only in the wettest of applications. This is why it is commonly associated with the applications of acrylic gesso, applied directly onto a wooden support. Areas of color mixtures or darker colors, especially when applied undiluted or more thickly, will not display noticeable discoloration in the same sense. If the entire acrylic painting is done onto an unsealed wooden surface, the levels of acids in the wood (which vary greatly from wood species and type) can cause damage to the artwork. The amount of acid or discoloration from a 1/8” edge is very small and will not put the painting in jeopardy of lasting or any continuous damage. The acid level in our hardboards is nearly neutral at that, and it is one of the reasons that we selected aspen as the overlay for our product. To sum up in reference to acrylic paint, if the drips or painted edge are white, applied quite wet, or thinly, discoloration may be noticeable. To prevent this, you can apply GAC 100 or PVA Size to the edges to create a barrier seal to the exposed, cut edges. For most painters’ practices, the effect of a few drips over the edge of a 1/8” thick panel is not damaging to the artwork or its appearance, and its durability is not at risk.

Gouache and oil colors are not susceptible to SID and the reason to carefully seal the panel before priming is again a rule of thumb, put forth by the general practice of acrylic dispersion grounds and acrylic based priming layers. The main issue with gouache dripping over the edge or being painted on the edge of a dark, brown panel is mainly that the edge may not be sufficiently absorbent to give a lasting mechanical bond between the paint and the panel’s edge. Also, the dark, brown tone may cause paint applications to look darker, requiring multiple applications.

For oil colors, there is also no risk of SID. The risk is more of great amounts of oil paint, directly applied to wood, soaking into the wood and oxidizing within the structure of the wood. This is even contentious amongst art conservationists and may be less of a risk than previously believed. The 1/8” thick edge of a panel will not allow for a risky level of oxidation within the wood support. The oils in oil colors will actually pass on some conditioning or preservation qualities to the wooden support, similar to applying oil to wooden furniture to recondition it.”

-Dana Brown
Artist & Customer Support at Ampersand


Click here to explore the full selection of Ampersand panels and tools.

Painting on Panel: Support Induced Discoloration

You may have heard the term “Support Induced Discoloration” or SID in relation to sealing panels or even gessoing a canvas.  And SID is the one reason that Ampersand encourages sealing panels before priming, but what does it really mean and how does it effect art long term?

Support Induced Discoloration is a relatively new concept to the art world, new because acrylic dispersion paints are new.  Support Induced Discoloration occurs when acrylic paints change color due to pulling up toxins or residue in the substrate.  The fluids in the paint leach into the substrate, through the primer and pull up the residue, leaving behind particulate in the paint that discolors it.  This is most apparent in transparent gels and mediums but also occurs to pigmented paint.  Gesso or primer is not sufficient in preventing discoloration, so sealing or sizing is always recommended.  

You can prevent SID from affecting your own work by properly sealing wood panels before use.  For more information on Sealing (or sizing) panels, refer to our previous post:
Painting on panel sizing.  OR, You can purchase one of Ampersand’s already sealed and primed panels, such as Gessobord™, Encausticbord™, Claybord™, Aquabord™ or Scratchbord™.  All of these panels have been sealed with Ampersand’s Archiva-Seal™ technology.

In the early 1990’s, Golden Artist Colors did some significant research with Buffalo State College to discover support induced discoloration and test the degrees of discoloration on different supports, with different acrylic mediums and primers.  The results from these experiments led to what we know today about SID.  

“SID contamination often goes undetected. In most cases, the paints applied contain a sufficient level of pigment, thus a strong enough color, to conceal the yellowing. However, in a transparent glaze and especially in thick translucent gel layers, SID becomes quite noticeable. SID can transform the appearance of an Ultramarine Blue glaze into a lower chroma, greenish color. Gesso alone will not stop SID, and different gels and mediums have varying degrees of blocking capabilities. The best product Golden Artist Colors produces to prevent SID is GAC 100. This thin medium works best when 2 or more coats are applied directly into the support. Once dry, the canvas can then be primed and subsequently painted with less potential for discoloration. Pre-primed canvases can be sealed with GAC 100 as well. Apply one or two coats onto the surface, and follow with at least one coat of gesso to regain tooth if needed.” — From the GAC website

Golden has neatly packaged the effects of SID on a masonite panel below in video format.  You can see for yourself in a few minutes how drastically a piece of art can change in a matter of weeks if the work is not sealed properly.


All things Ampersand, 
Karyn Meyer-Berthel 
Artist & Social Media Specialist 
Ampersand Art Supply 

Click here to explore the full selection of Ampersand panels and tools.

Painting on Panel: Sizing

All wood panels must be sized, or sealed, before painting to contain the natural chemicals within the wood that can break a painting down over time. Support Induced Discoloration (SID) occurs when a panel is not properly prepared and these chemicals leach through to the paint on the surface. By choosing a denser panel with a low acid content, an artist greatly reduces their risk of SID. However, all wood panels should be sized (sealed) and primed before painting to ensure their longevity.
Traditionally, panels were sized (sealed) with hide skin glue before applying the Gesso grounds. However, current research has shown that hide glues like rabbit skin glue do not completely seal the surface, and deteriorate over time. Conservators consider a PVA size or acrylic resin a superior modern substitute for hide skin glue. If you are sealing your own panel such as Ampersand’s Hardbord™, we recommend using GAC100 from Golden®. This is a superior sealer for panels. Its high resin content seals the panel very well and forms a good film on the surface. GAC100 also forms a good foundation for proper adhesion to layers of gesso. With Ampersand’s coated surfaces such as Claybord and Gessobord, Ampersand uses their Archiva-Seal technology to seal their panels prior to applying their painting grounds. This technology employs a specialized method to apply their proprietary sealers so that the actual fibers of the board are sealed. This sealing process creates a barrier between Ampersand’s acid-free coatings and the hardboard surface, ensuring that an artists’ work will be protected over time.
Prior to sealing, make sure your panel is clean of any dust or debris. Some experts recommend that you slightly sand the surface of the panel to ensure good adhesion. Note that Ampersand Hardbord should not be sanded. Removing the top layer of tempered fibers can cause the panel to warp when gesso is applied. Next, apply GAC100 liberally with a brush onto the panel. Take a putty knife or spatula and work the GAC100 into the fibers of the panel while it is still wet. Smooth it out and let this first layer dry. Next, apply two additional coatings with a brush, letting each layer dry in between coatings (no need to sand between layers). Make sure that the sealer is evenly distributed throughout the surface. It is highly recommended that you seal both sides of the panel to retard moisture penetration on the front and back and to equalize both sides of the panel to prevent warping.

All things Ampersand, 
Karyn Meyer-Berthel 
Artist & Social Media Specialist 
Ampersand Art Supply 

Click here to explore the full selection of Ampersand panels and tools.

Painting on Panel: Solid Wood versus Manufactured Wood Panels

Madonna and Child with Angels, Ferrarese, c. 1455, tempera on panel

Historically, rigid supports were used long before the adoption of flexible fabric supports. Most of the earliest icons still in tact from the 2nd and 3rd century are on wood panels. During the Renaissance a large portion of the paintings were also on solid wood panels. Italian painters were known to use poplar, while their Northern counterparts were using oak (later they would move on to mahogany). The wood was first dried well and sanded very smooth. It was then covered with a layer of liquid gesso made by mixing gypsum (a white chalk pounded into powder), with glue made from animal skins. Then, the wood panels were sanded and burnished until they were smooth, and ready for painting. The fact that we still have so many of these paintings with us today is proof that a properly primed and maintained panel withstands the test of time. 


Traditionally solid wood panels were used in the Renaissance and continue to be used by some artists today. There is a great variety of solid wood panels, so it is important to choose one that is rigid, has a uniform grain, and has a low acidity. Avoid painting on softwoods or semi hardwoods such as pine or poplar. These woods are more porous, making them more susceptible to warping, and also have a higher acid content. Due to the potential for warping, a solid wood panel should be at least 1″ thick. It is also important to note how the panel is cut. A radially cut panel will have the grain running perpendicular to the face of the panel, and thus will be more stable than the more common tangentially cut panels, whose cut along the grain will tend to cause warping or twisting over time. In addition, solid panels cannot be braced (cradled) on their back. Due to the varying rates of expansion and contraction across a panel, a rigid bracing would actually cause the panel to buckle and bow in order to constrain to the bracing system.

While the original panel paintings were all made on solid wood panels, there are many more options available for artists today. Technology has created numerous types of manufactured panels, engineering them to have very specific attributes, and eliminating some of the original weaknesses in solid wood panels. A solid panel still has all the original cellular structure of the tree from which it was made. This structure is susceptible to expansion and contraction as the wood is exposed to different climatic and environmental changes. For example, over time wood can warp or split moving from wet to dry climates. Manufactured panels in contrast, break down the cellular structure of the wood, enabling a more uniform, stronger, and stable panel that can weigh less.
Unlike the masters of the past, the modern painter has numerous choices available when it comes to choosing a panel for painting. Four of the main factors to consider are a panel’s:
1.    Density: The denser a panel, the less moisture it will absorb, making it less likely to warp. It is also easier to prime because the wood will not absorb the primer as quickly, reducing the amount of layers needed to seal and coat a panel.
2.    Grain: If a wood has a heavy grain, it will require more layers of gesso to ensure that the grain does not come through the coating. Also, within the same type of wood there can be great variations in density along the lines of the grain. Woods can grow more or less dense with varying temperatures through the year, or even in ‘stressful times’ such as drought, and this varying density can cause warps or cracks along the lines of the grain.
3.    Acidic Content: Considering the acidic content of the panel is important in order to avoid SID (Support Induced Discoloration – or yellowing). Softwoods or semi hardwoods, such as pine or poplar, generally have a higher acid content, and are more prone to causing SID through leaching. Hardwoods generally have a lower acidity, though we’ll see there are exceptions to this rule. It is best to do some research to determine what is the acidic content of the wood you are using before beginning to prime a panel.

4.  Type of Engineered Wood:   While engineered wood such as hardboard, plywood, and MDF can offer substantially better dimensional stability over solid wood panels for artists, it is important to understand the pros and cons of each of these surfaces and how different panels are braced.  In upcoming blogs we will discuss these differences and the differences in the materials used to brace panels.


There is a lot more to come on this topic, so stay tuned for more in the series:  Painting on Panel.


All things Ampersand, 

Karyn Meyer-Berthel 
Artist & Social Media Specialist 
Ampersand Art Supply 

Click here to explore the full selection of Ampersand panels and tools.

Panel Painting Tips: How to Seal Hardbord Panels

 

Hardbord™ is one of the few panels we offer unprimed and unsealed as a raw wood surface. There can be great pleasure in working directly on raw wood. However, for long term stability, we recommend sealing all unprimed wood panels, including our own, to protect against support induced discoloration (SID), warping and adhesion issues. Whether you’re working in acrylics, oils, encaustics, alkyds or tempera, paint will adhere best to surfaces that have been properly prepared using archival practices.
 

 

A size is a thin solution (often a weak glue) that is brushed directly onto a support. Sizing or sealing is recommended to protect Ampersand’s uncoated panels from support-induced discoloration (SID) when using  acrylic gesso. If wood is not sized or sealed properly before applying the gesso, yellowing can occur because water [a solvent] can cause acids, occurring naturally in wood, to migrate to the surface. In fact, it is extremely important  to properly seal any and all un-primed wood substrates to prevent support-induced discoloration (SID) that can cause your paint film to yellow over time. Hardbord™ is manufactured using Aspen fibers, a wood with a very low acid content, but it still needs to be sized and sealed. Sealing only the “paintable” side will possibly lead to warping if moisture or pollutants leach through the raw wood cradles or backing. So, seal the entire panel for the ultimate protection.  

To see first hand the effects of SID on a panel, check out this video from Golden:

 


To apply the size, use a wide flat brush to lay on 2 layers of GAC 100 or 4 layers of Gamblin PVA size, allowing each to dry completely before applying gesso layers. For more complete directions click here to read about sealing with Acrylic Gesso and click here to read about sealing with Oil Ground.


Some artists prefer having this work done for them, and by all means, feel free to purchase a Gessobord™, Aquabord™, Claybord™, Encausticbord or Pastelbord™ to suit your purposes.  Gessobord and Claybord, along with Hardbord, Encausticbord and the Artist Panel are all on sale right now through the end of September.  Find a retailer near you:  Fall Sale

All things Ampersand, 
Karyn Meyer-Berthel 
Artist & Social Media Specialist 
Ampersand Art Supply 

Click here to explore the full selection of Ampersand panels and tools.