Painting Surface

Another recommendation from Rebecca Crowell is lightweight  multimedia artboard

Accepts oil and water-based paints. No priming required. Can use on either side, flat or textured finish. Archival and non-buckling. Works with adhesives. 30"x36" Pack of 5 - White List - $83.50 Your Price - $70.98

I think I'm going to try these this summer. There are a variety of sizes and some specifically for plein air.