16 July 2008

Don't try this at home

One takeaway from the workshop way of life is the realization that there are some techniques and processes you just don't want to pursue on your own. That, in itself, is often worth the price of admission. You get to try something new without investing in equipment and supplies that you'll probably never use again. Last week's screen printing workshop produced two such "never again" conclusions.

One was devoré, the process that produces those beautiful cut-velvet scarves and other garments you see in stores. It involves applying a pattern using a toxic chemical solution that eats away the cellulose fiber (rayon or cotton, for instance) in your fabric, leaving the sheer silk backing. After the solution dries, you iron the treated portions til they turn the color of café-au-lait. At that point the nap starts falling off in those areas; rubbing gently usually gets rid of the rest of it.

All this time you're wearing a fume respirator -- not just one of those puny dust masks -- and rubber gloves. One runs the risk of starting with a too-hot iron and, peut-être, scorching portions of the backing fabric all the way to espresso. When rubbing off the nap, one might rub a hole in the delicate, now-compromised, silk. Ask me how I know this. Between the ambient toxicity and the fiddliness of the process, I strongly suspect that this might have been my sole attempt in life at doing devoré. Still, I'll mend the holes with silk thread and dye the piece, and perhaps produce a scarf that comes with modest bragging rights.

I hesitate to dismiss photo emulsion as cavalierly as I have devoré. It's an interesting process and fabulously versatile, but it requires a darkroom, a light box, and considerable deftness in applying the emulsion to the screen. You start by preparing a black line image -- an ink drawing, a stencil pattern, a photograph that you've tweaked in Photoshop to get rid of the gray scale values -- and copy it onto transparent acetate. In the darkroom, you coat a screen with a liquid light-sensitive photo emulsion and let it dry. Then you lay the acetate on a light table, position the treated screen on top of it, and expose the image for four or five minutes. Finally, you wash the screen quickly, under a strong spray of water, while the image gradually emerges on the emulsion. On the unexposed portions -- the parts that were black on your original image and on the acetate copy -- the emulsion washes away, leaving clear areas on the screen. From that point on, you work with it as with any other stencil; the clear portions allow the dye through, the coated portions block it. You can burn more than one image on a large screen and, when you print, mask off the ones you're not using. I used a public domain Japanese stencil design (thank you, Dover Books), and one of my own photos of a Japanese maple. Here's my first screen in its virgin condition:

And here are a couple of the prints I made with them. I'm pleased with the crispness of the black stencil on denim, and with the multicolor tree on a hand-dyed orange-y cotton:

Later I burned another stencil, a delicate bamboo pattern, on a smaller screen. It gave me eight or ten nice prints, and then started producing big blobs along one edge. I realized to my horror that the emulsion was peeling off. Apparently these things happen. It was nice while it lasted. I'll just think of it as a limited edition print run:

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