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All Things Ampersand

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.

3 comments on “Panel Painting Tips: How to Seal Hardbord Panels”

  1. This comment has been removed by the author.

  2. This reminds me, when I was around the age of nine. I painted a small country seen with acrylics on a scrap masonite type panel. Of course standards have changed, but, I had known of this issue very early on. I believe my mother still has that painting, some twenty years later. I predominantly paint with watercolor and encaustic these days- WC on paper, and encaustic… well, has become more sculptural than two-dimensional, but I am curious of any studies done specifically with wax? As I have many of my own experiences working with encaustic, I am more interested in, any long term studies surrounding this topic with encaustic, so to point others in the direction of further study and references.

  3. Hello Jonathan, thank you for writing. Are you speaking primarily of painting encaustic on Hardbord without priming?

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