Tuesday, April 9, 2013

Making hardboard painting panels - part 1

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[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.
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First, mark the outline of your panel, and rough-cut the panels to nearer the size you want. I left about 1/4 inch border all the way around the panel (so, for example, if you're making an 11 x 14 inch panel, you'll roughly cut it to 11.5 x 14.5 inches). The reason for this is that you don't want to force the router through a lot of hardboard, nor do you want to have to wrestle with the full-sized piece while you're cutting it. I used a jigsaw for this step, and ended up with manageable panels like the one in the picture above.
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Next, put several small pieces of double sided tape onto your straight edge. I used a 3/4" thick piece of poplar for mine. I put about 3 pieces of 1 in long tape, per 12 in of panel. Then turn the straight edge over and align it with the outline of your panel you marked earlier. Put the straight edge right on the line and push down hard to make sure the tape tightly bonds the panel surface and the straight edge. It's better to adhere the straight edge to the slick side of the hardboard, not the textured side. The picture above shows the straight edge affixed to the panel.

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.

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At this point I flipped the panel upside-down and moved the straight edge so that it hung down over the edge of the table toward me, which puts the slick side of the panel face down on the table surface, as above.
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Here is a view of the flush-cutting router bit. I use the 1/4 inch one. The ball bearing follows along the straight edge, and the sharp blade below it cuts the hardboard panel. This step is very messy, which is why I am outside, even out of my garage. Hardboard dust goes everywhere and is very fine.
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Then, just make the cut! Be careful. You should end up with the above. The hardboard fibers are a little fuzzy after cutting, so knock those off with a piece of 220 grit sandpaper. Repeat until you have a satisfactory number of panels. I think I did six in about an hour.
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That's four 11 x 14 inch and two 12 x 16 inch panels. The next step is to wipe everything down with rubbing alcohol, to clean off the dust and whatever surface oil is on the panel.
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[Edit: Follow this step if you are using acrylic gesso, but if you are using oil ground, you can skip it.] Apply a coat of Golden GAC-100, which is a Multipurpose Acrylic Polymer that seals the hardboard and keeps any lignin or contaminants from migrating up into your painting ground or painting. This is the reason it doesn't really matter whether you use tempered or untempered hardboard. I brushed it on with a cheap paintbrush. This turns the boards a lovely walnut color. There's no real need to put it on the edges or back of the panel. After this is dry to the touch, apply a second coat. Allow the GAC-100 about 2-3 days to dry completely, and then apply the ground of your choice. More on that in the next post.