Art week addendum: buckling paper

Stolen shamelessly from Blick, obviously.

So I just read something interesting and had to share.

When you use wet media on something, and the paper goes all wavy?  That has a name.

It's called "cockling".

Yes, it sounds like a baby rooster.  But it's actually science.

See, the way they make paper is this:

Fibers of various kinds -- tree pulp, cotton, linen, other stuff -- are mulched and pulped and essentially shredded into individual fibery bits.  Those are flattened out into exceedingly thin, flat, even layers.

Those layers are then stuck together with some kind of glue into thicker sheets, and then dried.  How they're dried determines the finish.  Cold press is, y'know, cold pressed on big drums.  Hot press is essentially ironed into having that super-smooth texture with very hot drums.

(I'm assuming rough is created by bored wizards between spelling cows to fly or whatever they do.)

All of that is the finish, but the main bit -- the fiber layers -- are the same for everything.

Some have sizing in them, which keeps the paper from eating water like a hungry sponge, too.  In fact, the sizing is what separates watercolor paper from, say, a cheap dimestore notebook's finish.

So then, it gets to you, and you put watery stuff on these fiber layers.

And here's where the magic happens.

All those fibers in there, which have been nestled neatly together in organized rows, are reactive to water.  If you've ever seen a wooden window frame when the rain gets in, you'll know what happens to plant fibers that get wet: they swell.  And these fibers are no different.

Imagine for a second that you glued together about a hundred of those Grow Your Own Insects into a flat sheet shape.  (You know the ones.  The ones that come in a capsule and you put them in a glass of water, and in an hour, you have this huge super cockroach or something that's 100x the size of the original capsule.)

Or a boyfriend, apparently.

If you dunked a strip in the middle of the group into water, in about an hour, you'd have a strip of giant insects, with the other, un-wet toys still their original size.  It would not even remotely be flat anymore.

This is what cockling looks like, only much, much smaller.  

The wet fibers suck up water and expand, which soaks out into the fibers next to the originals, which also expand.  They push outward, but are still constrained by the glue between layers and the dry, more rigid bits at the edge.  They grow into kind of a cup shape, creating valleys made of expanded fibers in various stages of expansion.  The dry parts are pushed up into peaks.

Voila.  You have wavy, not-at-all-flat, cockled pages.

Personally, I don't mind wavy papers in my journals.  Means I worked on those pages and I get a little prideful about finished pages.  Some of my journals have pages that are so cockled that the book puffs open like a fan, barely able to be contained by mere binding anymore, even.

If you want to avoid cockling on bound pages, you need books with thicker papers.  The finish doesn't matter as much as the thickness for this issue -- all papers of all finishes will react similarly with exposure to water.  The degree to which this happens depends on the thickness of the underlying number of layers, which prevent the swelling from taking the whole page with it when it goes rogue.

For unbound sheets, stretching your paper in advance will take out most of the problem, since the WHOLE page is wet down at once, and then flattened out and left to dry evenly across the surface.  Since the fibers are dried with some room between them that way, the water expansion won't affect the neighboring fibers as easily, and you won't get the ripply bits.

Blick has a good youtube video on stretching watercolor paper, if you're interested.

Science, man.  It's awesome.

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