Turning Your Sketches and Lineart into Printable Bluelines: Watercolor Basics

I've covered blueline conversion a few times in this blog- from dropping your bluelines to turning your roughs into bluelines.  This is a pretty common process in my comic creation, and my comic pages go through dropping and turning into bluelines several times before we reach the finished page.  Just last week, I covered creating and printing bluelines for your comic work, so if you're missing a step, check out that post.

You can also use this process to help you create watercolor illustrations.  This is a particularly appealing idea to digital artists who are interested in practicing traditional techniques.  Rather than struggle with completing the entirely process traditionally, you can do your sketching digitally, and only worry about handling the final stages in watercolor.

You can start with a digital sketch like this:

And after a few clicks, end up with printable bluelines like this:
Or start out with a traditional sketch like this:

And after a few clicks, end up with this:

Why would you want to convert your lineart to bluelines?

Inkjet inks are water soluble, which means they'll dissolve as soon as you stretch your watercolor paper.  To prevent the blue from leaving a cast to the paper, I add an additional wash and wipe off step to my paper stretching, but otherwise it does not alter my watercolor process.

Yes, with a toner based printer, you CAN print your lineart onto watercolor paper

But this comes with several caveats.  Most home toner printers can't handle heavier paper stocks- not even 90lb student grade watercolor paper.  Even most professional machines can't handle heavier stocks- the machines at Office Depot can only handle 90lb watercolor paper, and it requires someone who's quite familiar with the machines to figure out the right settings.  Goodluck getting that.

Toner based ink is waterproof- great if you want to print 'inks' onto your paper, terrible if you're hoping the dye based printer ink will wash away leaving just pencil lines behind.

Converting Your Sketches to Bluelines:

Begin with the file you want to print.

Convert your image to Grayscale by going to Image-Mode-Grayscale.

Then, to drop all the extra lines, go to Adjustments-Curves.

And it will bring up a graph.  Bring the front of the graph all the way down, and the back of the graph all the way up.  Adjust until you find a setting that drops out most of the extra, lighter lines and darkens your remaining lines.

Then go Image-Mode-Duotone

And follow these settings to create bluelines.

And voila!  We have our bluelines, ready to print.
In my next installment of Watercolor Basics, I'll show you how to print these bluelines out onto watercolor paper using a printer you probably already own!


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