illustrated playing cards
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DIY PAPER STRETCHER
One of the tricks that's helped me get the most out of my materials is paper stretching. I like to use tinted pastel paper as a base for my oil paintings, but it's too thin to handle water media without buckling. In the past, I've mounted the paper on board, but this method has its own host of problems (lots of tedious prep work, the risk of warping) - not to mention storing and transporting panels (even relatively light illustration board) can be a hassle. Paper stretching is a much quicker process that's thriftier with materials and (in my experience) less likely to result in disaster.
There are a few paper stretching methods commonly used by watercolor artists - tape, staples, glue - but I've had pretty poor results with all of them (possibly because the paper I'm using is thinner than those traditionally used for watercolor). I recently built a paper stretcher (inspired by this post on Wetcanvas) - it cost me about $50 to assemble, but it's sturdy, infinitely reusable, and beats ever other method I've tried.
PLANNING & SUPPLIES
For the purposes of this tutorial, I'll be providing measurements for a stretcher that produces an 11x17 image - but you can use the sizing info to plan your own in any size.
- A - The printed area of your image (11 x 17")
- B - The total canvas size (11.5 x 17.5")
The canvas (the area of the paper that will be exposed once the paper is mounted on the stretcher) should be 1/4" larger than your image on all sides - bad things can happen along the edge of the stretcher (sticking, tearing, etc), so it's good to have some wiggle room. And, since you'll need to trim right along the stretched edge, you'll want the extra border so you'll have more room for matting/framing.
- C - The total paper size (12.5" x 18.5")
Add 1/2" inch to the canvas size on all sides to allow some overhang for the stretcher to grab. Most watercolor/pastel papers are around 19 x 25.5", so you can use one full sheet for two 11x17 paintings.
- D - Plexiglass (11.5 x 17.5")
Cut your plexiglass to the same dimensions as the total canvas size. The plexiglass needs to be at least 3/32" thick in order to create enough of a lip to hold the paper in place.
E - 1/2" thick* Gatorfoam Board (12.5 x 18.5")
This stuff is fairly expensive, but regular foam core isn't strong enough to resist warping. Cut the gatorfoam 1/2" larger on all sides than the plexiglass to accommodate the width of the flat stock & u-channel. I bought mine online at Dick Blick.
- F - Aluminum Flat Stock, 1/8" thick by 1/2" wide (56" length)
Add all four sides of your image size to get the necessary length - make sure you factor in waste when planning how much to buy - this stuff is usually sold in 2- or 4-foot lengths. I found mine at Lowes.
- G - 5/8" Aluminum U-Channel (56" length) Same as the flat stock - add all four sides of your image size to get the necessary length, and factor in waste. Also found at Lowes.
* Gatorfoam is also sold in 3/16" thickness - you can make a stretcher out of the thinner board, but you'll need to substitute 3/8" u-channel and 3/16" flat stock (thickness of gatorfoam + thickness of flat stock should equal the depth of the u-channel). I wasn't able to find either of these locally.
Once you have the materials in hand, assembly is pretty simple: measure (twice!) and mark the gatorboard, plexi, and aluminum; cut to size. You can use a box cutter for the gatorboard, a score-and-snap plexi knife for the plexiglass, and a hacksaw for the aluminum.
Mark 1/2" from the edges of the gatorboard to accurately position the plexiglass; you can glue the plexi to the gatorboard for a more permanent solution, but I just use double-sided tape to secure the layers.
PREPARING YOUR ARTWORK
Original pencil drawing (left) and print (right)
While it's possible to stretch an original pencil drawing, I prefer to work with a print. It makes success on the first try less critical, and lets me paint on a different kind of paper than I use for my drawings. To prepare your file for printing:
- Scan your sketch at 300+ dpi.
- Adjust your sketch.
In Photoshop, use the Curves and Levels adjustments to your liking - you want your sketch as close to pure black and white as you can get it without losing the detail and subtlety of your drawing. You may want to experiment with a few prints at different levels of opacity - I generally lighten my sketch a bit, aiming for around a 50% gray: light enough that the print won't show through in the finished piece, but dark enough that it won't disappear under the first wash of ink. I usually add a low-opacity, 2-4 pixel wide border around my artwork before printing, to allow accurate placement on the paper stretcher.
- Scale your image to account for directional paper stretch.
Paper tends to stretch more in one direction than the other, so you'll want to scale your image accordingly; the exact percentage of stretch will vary depending on the paper you use, but around 2% seems to be typical.
If the exact dimensions of your finished piece are crucial, you can figure out the degree of stretch by cutting a 10x10" square of paper, marking the width and height, soaking for five minutes, then measuring the new width and height. Multiply the extra length or width you've gained by 10 to get the percentage of stretch (for example, if your paper is now 10.25" wide, you can plan on a widthwise stretch of 2.5%).
Once you've figured out your percentage of stretch, adjust your image to account for it. In the Image Size dialog box, uncheck "Constrain Proportions", and enter your new width as a percentage (for paper with 2.5% stretch, this would be 97.5%).
I bring my adjusted file and chosen paper to a local shop that does giclee printing. For small pieces, you may be able to use your home printer (although you'll want to do some tests beforehand to make sure your ink is waterfast/smudgeproof - mine isn't!). Make sure you mark the wrong side of the paper (if applicable) and, if there's any doubt, indicate the width and height so you don't end up with a print that stretches in the wrong direction.
SOAKING THE PAPER
Soaking the paper before stretching allows it to expand fully, preventing the uneven buckling you get when painting on unstretched paper. To prepare the paper:
- Lay the paper flat on a large piece of plexiglass (a clean tile floor or bathtub also works), and mist with a spray bottle. Flip the paper over and mist the other side; repeat as needed until the paper is thoroughly soaked - the entire surface should be shiny, right up to the edges. You can gently spread the water around with your hands to make sure it's uniformly wet.
- Set a timer - two to five minutes should be plenty. While you wait, keep an eye on the paper - if any part of the surface begins to look matte, mist it with more water on both sides.
One trick to make sure the paper has fully expanded is to measure the printed image in the direction of stretch. If your calculations have worked out, the print will expand to the exact dimensions of your finished image size.
USING THE STRETCHER
- Position the paper.
Lightly blot the back of the paper with a paper towel to absorb excess water before positioning it on the stretcher. Holding the paper by its corners, line it up with the edges of the stretcher and lower it onto the plexiglass. Feel around the edges to make sure the printed area is centered on the stretcher, not touching the edges or extending over the plexiglass at any point. It's helpful - although not absolutely necessary - to have an extra set of hands for this stage. If you find the paper's placement is crooked, just peel it up and try again - if the paper starts to dry while you work, you can always give it another misting with the spray bottle and repeat the process.
Once the print is centered, gently smooth it out with your hands, starting at the center and working towards the edges, to make sure there are no wrinkles or air bubbles.
- Secure in place.
Position one piece of aluminum flat stock - it should be centered between the edges, and butting up against the edge of the plexiglass to crimp the edge of the paper and sandwich it against the gatorboard. Slide the aluminum u-channel over the flat stock/gatorboard sandwich to secure it. Make sure to slide it all the way up against the edge of the gatorboard - I like to hold the stretcher on edge and press the u-channel against a hard surface (table, floor) to make sure it's secure. Repeat with the opposite side, then the remaining two sides. If you notice any large bubbles or wrinkles, you can remove the u-channels and try again - but it's best to handle the paper as little as possible to avoid tearing. The paper will contract as it dries, so smaller imperfections will usually disappear on their own.
- Air dry.
Keep the stretcher horizontal, and don't handle it until the paper is completely dry (usually at least a couple of hours - always err on the side of caution!). To speed the drying process, you can blot the surface with paper towels, or place a weighted sheet of watercolor paper on top of it to wick water from the surface. DO NOT, under any circumstances, attempt to speed the drying with a hair dryer or by putting the stretcher in direct sunlight or near a heat source - this will dry the exposed paper much faster than the aluminum-encased edges, which will result in tearing.
If an edge DOES tear during the process, you'll have a couple options - starting over with a fresh print, gluing a strip of paper over the back of the tear and repeating the process from square one, or re-stretching on a smaller stretcher - but it's best to avoid the situation altogether.
Once the paper dries, I usually mark the very edge of the "canvas" with pencil - this gives me a visual guide so I can tell if the paper starts to pull free of its clamped edges.
Your paper will now stand up to any wet or dry media you can throw at it. Watercolor and acrylic ink are two of my favorites; the plexiglass also offers a nice hard surface for pencil, colored pencil, and charcoal. If you want to use oil paint, apply 3 coats of acrylic matte medium (masking the edges to avoid gluing the edges of the paper to the aluminum, and allowing the paper to dry thoroughly between coats) to protect the paper from the oils. Remember to keep the stretcher horizontal if you're wetting & air-drying large areas of the paper at a time.
You may occasionally get a little bit of rippling/buckling in the paper - especially if you apply a couple of very wet washes without allowing the paper to dry completely in between. Don't panic! If your edges are still secure (check the pencil line you marked around the canvas to make sure), the paper will stretch flat again as it dries - just give it a couple of hours. Worst case, the paper can almost always be removed from the stretcher, spritzed with water, and re-stretched... gently.
When you're finished with your painting, carefully remove the aluminum u-channels, peel away the flat stock (watching for any spots that may be sticking to your painting), and trim away the stretched edges of the paper.
Now all that's left is to enjoy your work on paper - easy to store, easy to frame, cheap to transport. And SO PAPERY! Wasn't that better than painting on a slab of masonite like a normal person?