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From the author of The Blob Brush Tool (AICS4)

The Blob Brush Tool (AICS4)

There are a whole lot of strange things about this tool, and it may take awhile for you to get the hang of when you might use it. In fact, I didn't warm up to this tool for quite a while. The Blob brush uses your current stroke color as the style, but as soon as the mark is made, your object that creates the look of a brushed path is actually filled with the color, and not stroked at all. The marks look like the Calligraphic brush (more about this later), but instead of behaving like a live brush mark, they behave like "expanded" brush marks (you can't adjust the "spine" or inner path once it's created, just the edges of the path).

I couldn't understand why you would bother with an expanded brush, but that's the key: It's not really a brush at all. While all the other "brushes" are controlled by the Paintbrush tool in the toolbar, the Blob brush is its own brush in the Toolbar. If you double-click the Blob brush, you can set preferences for the tool, including those that control whether the marks that you make with this tool will join with other marks that are styled the same (Keep Selected, and Merge Only with Selection), and how accurate or smooth your marks are (the Tolerances settings).

But one of the strangest things about this tool is that, although the bottom set of objects allow you to customize the size, shape, and behavior of this tool, you're not going to want to bother to use this setting. Instead, strangely enough, the Blob brush tool (which, remember, isn't a brush) will inherit the properties of any Calligraphic brush chosen in the Brushes panel. Or, if you select a Calligraphic brush mark made on the art board that also will set the styling for the next Blob brush mark that you make.

Once you've set the styling for the next mark, as with Photoshop you can use the bracket key [ to decrease the size of the mark, and ] to increase the size. If your Calligraphic brush has pressure-sensitive settings related to size, and you are using a pressure-sensitive graphics tablet, then your Blob brush can take advantage of those settings as well. And, like the Bristle brush (as described above), your cursor will preview for you the actual shape and size of your currently selected "brush" tip. The real power of this "not brush" is that you can:

  • Use the Eraser tool to reshape the contours and edges of a path
  • Add to or join objects that are styled with the same fill color

It’s cryptic to explain but fairly easy to use. Figure 3 shows an example of a painting of a “Vegetarian Cheetah” by Lance Jackson (featured in The Adobe Illustrator CS6 WOW! Book), and a series of “in process” stages of one of my portrait drawings (featured in the “Artistic Painting with Illustrator: Natural Media Brushes” course on, see" for more info on this).

Figure 3 An example from The Adobe Illustrator CS6 WOW! Book of a Blob brush painting by artist Lance Jackson, and a Blob brush drawing by the author with a YouTube excerpt from her “Artistic Painting in Illustrator: Natural Media Brushes” course for explains the process of creating her Blob brush drawing.

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