BLACK AND WHITE | MASKING SHADES OF GRAY | WHAT ABOUT BLACK PLEXI?
Please note that illustrations used here and on our website are for informational purposes only.
This topic covers the properties of etching on acrylic, plus tips on how to submit etch artwork. Please note that we no longer accept full panel etching, only 5"x5" partial etch.
Our laser etch machine is quite precise, etching onto acrylic at more than 600dpi. Therefore, artwork that is not submitted at least 300dpi - optimal resolution for print - can appear fuzzy. We can't compensate for that. For more information about how resolution affects printed artwork - which is similar to etching - please review the article Screen Versus Print - A Helpful Guide.
Black and White
The process of etching uses the laser to create successive frosted lines onto cast acrylic. In software, the laser etch machine interprets the color black as an area to fire the etch laser, and white as an area to skip.
This means that for the most faithful reproduction onto acrylic, we need artwork in black and white. Grayscale, or images that have varying intensities of black or white, will also etch, but as white dots of varying size and density.
In the below example you'll see a very closeup view of how the laser etching machine handles grayscale content - top to bottom, from dark to light.
In the photo above, areas that were depicted as shades of black were etched onto the acrylic, and white was skipped. The areas in white are transparent because the acrylic below it is clear.
This leads to the question: How do we get that end result, when we start with an illustration like this?
Masking Shades of Gray
The end result was created using three techniques - converting to greyscale, inverting, and masking. First, the image must be turned into grayscale in your graphics program.
In Photoshop, this is done by selecting Image > Mode > Grayscale. It will look like this:
In the image above, the dark areas would leave a frosted etch onto acrylic. However, we're not done just yet. This is how it would look if you tried etching it as-is:
Inverting Your Photo
As you can see, when etched onto acrylic, the image produces what is considered a photo negative. Again, what is black in the photo or illustration, will etch as frosted white onto the acrylic. To partially resolve this, you must invert the photo, or swap the colors to their opposite. In this case, black is inverted to white, and vice-versa. So let's look at the photo in question, inverted:
I say partially resolve, because if we recall the etching process, everything that is non-white will etch onto the plexi. Let's look at an example of the etched plexi - this time with a blue background to better illustrate:
This - of course - does not represent the end result, either. You want the image to display etched areas from dark portions of the photo, but the background should be clear. To do this, you must create a "mask" of the item you want to remain in the foreground, and etched.
Masking a Foreground Image to Remove Background
"Masking" is a technique to hide parts of an image that is undesired. In photoshop, this is done by creating a layer mask. For the purposes of simplifying the explanation, I'll use another photo to illustrate - a smiley face with a simple circular shape:
We want this smiley face clip art illustration to etch without a white background:
If we process the artwork in the same manner as the previous photo of Ryu, it will look like this:
If we tried etching that on acrylic, we end up with a similar result as before:
Instead, let's create a mask the for the circle shape that represents the foreground subject. Worth noting, if you are using Photoshop, make sure the new document you place an image into has the background set to "transparent", or you won't immediately see the transparency that is created by the mask.
In photoshop, you first create a selection around the shape of the subject, then click the "mask" icon in the layer.
With the layer mask in place, anything that is not part of the mask (what appears in white within the mask thumbnail) will not appear. Photoshop displays transparency via the checkerboard.
I chose this smiley face image to illustrate the technique over the photo of Ryu due to complexity. The more complex the image, the more steps needed to achieve transparency of the background via masking. For the Ryu image, I performed a number of tricks to mask it, including drawing a custom mask for the foreground photo, and employing other methods to leave some elements as black, such as the smoke behind him. The magic wand tool can only do so much.
A detailed explanation of how layer masks work, as well as clipping masks, is available via designshack.net. Definitely worth a read.
What About Black Plexi?
Black Plexi is opaque, which means the artwork must be etched on top of the plexi instead of under it. Additionally, the etch artwork will not appear perfectly white, but dimmer due to how a laser etches on black cast acrylic. Here is a great example of black plexi with etching:
Photo courtesy of Twitter's @eljaykooljay
Remember that any portion of the artwork that is black will etch onto the acrylic; any portion of white will not etch. This is also true of black plexi.