ABS plastic panel

​I am just an artist, and not a conservator or specialist but I had previously read this interesting patent for a ABS plastic panel with a clay/acrylic top-coating:
https://patents.google.com/patent/CA2622593A1/en
we have focused on ABSpolymer sheets and have conducted experiments to ensure that the product that is developed actually works on an ABS plastic surface. We have found that certain polymers, such as polypropylene and polyethylene, have waxy surfaces and are not suitable because the soft gels will not properly adhere to them. However, we have found that when the soft gel is applied to an open (sanded) surface of an ABSplastic surface, and allowed to dry, it is difficult to scrape off the ABS surface, even with a knife. We have found that Golden’ soft gel gloss, available from Golden Artist Colors Inc., New Berlin, NY, is satisfactory as a base layer on the roughened ABS polymer surface.
The invention relates to a method of treating the surface of a polymer so that it is acceptable for watercolor pigments comprising: (a) roughening the surface of the polymer; (b) applying to the roughened surface a layer of 50% soft gel gloss mixed with a 50% kaolin clay and allowing it to dry; (c) sanding layer (b) after it is dry;(d) applying to layer (b) a second layer of 50 % soft gel gloss mixed with 50 % kaolin clay and allowing it to dry; (e) lightly sanding the second layer (d); (f) applying to layer (d) a layer of 50%kaolin clay/water mixture and allowing it to dry; (g) lightly sanding layer (f); and (h) applying a layer of absorbent watercolor ground to the layer of kaolin clay and allowing it to dry.

There is more information in the patent about their process and how long it take to remove with an electric sander as well.

I hope this is useful to you.
Richard

​Thank you, Richard, for your comment. This helps.  It seems that there might not be anything inherent to the ABS panel that is impermanent; one just needs to get stuff to really stick mechanically. When I am in doubt, I scrape it with a fingernail to see what comes off. I doubt the bond gets stronger with age.
Regards,

Clay