[Note: this post originally appeared on my blog at http://www.westonhobdy.com in January.]
I've been experimenting with different methods of making my own hardboard painting panels for several reasons. For one, it's much cheaper than buying them: a 1/4 inch thick, 4 x 8 ft sheet can be purchased for around $14, and will produce roughly twenty-four panels in the 11 x 14 inch range. Compare this to Ampersand Gessobord, which runs $7.82 for a single, 1/8 inch thick 12 x 16 inch panel. (Though I do believe they make a fine product.) A downside is that it's a little labor intensive, but with the DIY approach and good materials, you can be completely confident you're painting on a high-quality, archival substrate.
What makes these archival, you ask? The method outlined below is basically the procedure given in The Painter's Handbook by Mark David Gottsegen, which is an excellent book that describes sound painting practices. It's fairly new and up-to-date. Gottsegen suggests bracing the panels to counteract warping, but with the 1/4" thick hardboard and fairly small panel sizes, you don't have to worry about it much. Otherwise, I've followed his method closely. A few points to remember: he says it doesn't matter if you use tempered or untempered board, which has been a long-standing issue for painters. In fact, tempered can really be better because it's denser/stronger. Also, do not sand the panels before applying the size and/or ground, as it "opens" the painting surface and allows contaminants to seep up into the painting ground. Lastly, to really seal out any contaminants that might be in the hardboard, he recommends [edit: for acrylic gesso grounds] applying a size (see below). This prevents surface-induced discoloration (SID), which is explained nicely here.
I don't own a table saw, so I've been cutting the panels with my router, a flush-cutting bit, and a straight-edge. This really produces a very clean cut. The biggest challenge for me was to find a way to secure the straight-edge to the panel without getting in the way of the router's path. The trick is to use double-sided tape instead of c-clamps (or whatever). Nothing sticks up in the way of the router, so you can make a continuous, straight cut. At some point, I plan to make a few jigs in common sizes (11 x 14, 12 x 16, 16 x 20, etc.), that I can affix down with the double-sided tape and not have to move the straight edge around for each side of the panel. That will definitely cut back on some of the time involved. That all said, here is the process.
Update: In lieu of a straight edge, I've started using a cradled panel as a pattern for the size panel I want to cut. I put the double-sided tape on the panel surface itself, and stick that down to the rough side of the hardboard. Then you can zip around all four sides with the router without having to stick and un-stick the straight edge four times. Much faster.