cracking on true gesso ground

Are these on plywood? I have seen this happen innumerable times on that substrate. That is why we generally recommend applying a fabric overlay on wooden panels to help mitigate cracking. Unfortunately, while the checking may not become worse in the gesso, it could certainly propagate through your later paint applications. This leaves you three options. First, leave it as it is knowing that the paint will very likely crack. This is probably the worst option. Second, sand the gesso off completely and start over. I know this is a pain but it is probably the best course of action. Third is sort of a compromise and may or may not prevent future cracking. Make a rubbing pad (similar in shape to those used in French polishing) by folding a sheet of smooth lint-free fabric. Wet the pad with water and rework the surface of the gesso in small circular motions. This will, ever so slightly, reactivate the gesso at the surface. Continue this past the point where there are no signs of cracks. The more fully and longer you do this the better chance you have of success. You should set these panels aside for a good period of time to see if the cracking returns. Again, there is no guarantee that you have completely solved the problem as the technique really only reactivates the surface.

MDO may or may not be a good alternative. I personally would avoid using it for artworks meant to be permanent until it has been sufficiently tested for this purpose. These boards are primarily used for outdoor signage which is intended to last about 7-10 years. I actually subsidized my early art career as a sign painter at a sign company and painted on many dozens of MDO panels. I particularly worry about the resin impregnated paper overlay in terms of long-term stability as well as general appropriateness for glue grounds. We have a few comments that are germane to this discussion in our Myths, FAQs, and Common Misconceptions download, especially number 13 but also number 11 and even number 15. I welcome any additional data about MDO which could alleviate my apprehension. Baade, Brian

​We have been big fans of MDO in all of our testing and have worked with innumerable mural applications over the years where it has gheld up well. Keep in mind that by definition all plywoods are commercial products and as far as construction goes we think MDO are among the more solid. Part of this comfor level comes from finding it listed among the “best options” for wood panels in the follwing document compiled by the CCI:
https://formacaompr.files.wordpress.com/2010/02/guidelines-for-selecting-materials.pdf​
Granted this is for materials listed for use in exhibition and storage, but at least speaks to some testing in regards to off-gassing. But do agree perhaps more longterm testing would be nice – but given the choices, it seems one of the less concerning. At least to us.

Sarah Sands
Senior Technical Specialist
Golden Artist Colors

That is good to hear Sarah. I was in agreement about the suitability for outdoor murals and exhibition construction but am happy to hear that you have had good results as a fine art substrate.

Sarah Can you tell me what grounds and conditions you used to test the MDO? Did you specifically test animal glue gessos or only acrylic dispersion grounds? If only the latter, I think that I will devise an experiment with this and a number of other grounds to get a sense of MDOs applicability as a fine art substrate. It it is successful, this would be a real benefit for those working on glue grounds as there are a number of issues with many of the commonly used substrates out there (birch plywood, hardboard, MDF, ACM, etc) as substrates for egg tempera paintings.