Watercolor Paper Stretching question

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Watercolor Paper Stretching question

Postby mjs » Mon Nov 02, 2015 4:31 pm

Being new at this watercolor thing I've been asked a question which has raised more questions and I thought that perhaps the community here could help.

I've "stretched" (thoroughly wet, tape flat on a waterproof surface and let dry,) watercolor paper before use as I've read was a good idea to prevent the paper from curling when wetted after being painted, mostly 140 lb (200-odd GSM) paper and it works ok for me although I've since decided that buying paper in blocks is a more convenient solution. I understand that stretching heavy paper (250 lb. - 370 GSM or heavier) paper is unnecessary and that has proven to be the case as well. My daughter wanted to use a graduated watercolor wash (quite wet) on very thin paper (about 12 lb -- 18 GSM) and asked me whether stretching the paper would help keep it flat for additional colored pencil work. I told her that I had no idea and have no such paper laying around to test. That raised another question -- does stretching the paper help prevent any paper from buckling or developing waves when wetted, or is there a lower limit to the weight of paper which can be preserved more or less flat with this method? For those of you making your own watercolor sketch books, do you stretch the paper you put in the books before you make a book out of it?

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Re: Watercolor Paper Stretching question

Postby Andre Jute » Mon Nov 02, 2015 6:52 pm

I make my own sketchbooks* by ripping down 300gr imperial sheets to quarters, then folding them to 11x7.5in, and I don't pre-stretch the paper. It buckles very little at these sizes, even up to quarter sheet, and putting stuff on the closed book flattens the pages again.

* http://www.sketching.cc/forum3/viewtopic.php?f=2&t=2163&start=225#p20736
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Re: Watercolor Paper Stretching question

Postby Rebecca » Mon Nov 02, 2015 8:46 pm

I have a couple ways to put washes on thin papers

For sheets of paper:
First, do any preliminary drawing with non-soluble media (I use graphite or permanent ink). Wet the back of the paper to expand it. It will curl at first. Re-wet if corners and edges dry out while still expanding. Take care not to get water on the reverse side. To help prevent seepage, place the paper (top side down) on a towel, or support it with a dry hand from the underside. Once expanded, place on a plastic board, damp side down. Be sure there can be no puddling around the paper, then roll it down with a rubber brayer. While the paper is still flat against the board, apply washes. As the paper dries, it cockles, which means it warps in two directions, forming bumps. Guide this tendency into a one direction roll. Once dry, flatten this slightly rolled paper under a weight. Wetting the back of the paper gives slightly softer wash edges than you get if painting onto bone dry paper. It's not a bad look.

For sheets of paper, or in sketchbooks:
Use gravity to pull washes thin, which helps the paint dry before the paper becomes saturated. You need to work from the top to bottom. Tilt the paper as washes are applied. When you hit the edge of a color zone, use the depleted brush to suck off any bottom puddling. This method can easily provide graduated washes with smooth transitions. If you want spidering in your washes, this method will not work.

And paper contracts each time it dries. New washes that soak a once-stretched paper will expand and buckle the paper all over again.

Also, if you stretch any watercolor paper and let it dry while taped or pinned, and then soak it again while still bound this way, it'll expand and warp. Buckling won't be so extreme, though. Lighter weight papers will buckle more than heavier papers. Each time, as papers dry while bound in place, they become flat. A large sheet of light-weight paper can tear from the stress of shrinking as it dries while bound. But a smaller piece of the same paper can withstand shrinking while bound.
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