Introduction: Charcoal and Acrylic Laser (Raster) Etchings

By Yulia
About: I believe in slow craft, carefully observed hand made objects. Currently I'm an Artist in Residence at Autodesk Pier 9, San Francisco, CA where I am learning to understand Computer Aided Machining, additive …

For the last few months I have been an Artist in Residence at Autodesk’s Pier 9 workshop, a state of the art industrial shop and advanced manufacturing facility. Artists of diverse backgrounds are invited to train on software and equipment, as well as encouraged to use these new industrial technologies in unconventional ways. With this in mind I began collaborating with the latest machines to create a new type of painting. The work that grew out of these investigations looks for the tension between digital and analog processes. These paintings of new geologies are based on autonomous robotic photography of NASA, ESA and JPL labs and created in part by hand and in part with Epilog’s and Meta Beam laser cutters. As I collaborate with these machines, be it my MacBook pro, the JPL instruments on the Mars Rover or the Metabeam and Epilog lasers at Pier 9, I embrace the glitches that occur throughout the process, viewing each glitch as our machines opportunity for creative self-expression. Creating a truly collaborative human + machine paintings.

If you wish to learn more about my work at Pier 9 please check out my artist lecture. The laser etching part starts 15 min into the talk.

Step 1: Prepparing Plywood Surface

I approached this project the same way I would any painting or drawing with care and longevity in mind. In order for the finished artwork to age well, it's important to carefully seal and prepare a good painting surfaces using high quality archival (acid-free) materials.

I start with a birch plywood painting panel. You can purchase these at most art stores in a variety of sizes and depths. The ready made panels can be quite expensive and limited in size. I now make myself custom ones using sheets of 1/4" inch Russian Birch Plywood and 1x1" or 1x2" Bass wood or Poplar wood strips for the back frame supports.

Prepping your Wood

Step 1: Apply a coat of professional gesso, (white primer with marbling dust) Applying several thin even coats works best. Use long steady strokes all going in the same direction (left to right or top to bottom.A wide foam brush will aid you in achieving a nice smooth surface.

Step 2: Allow each coat of gesso to dry thoroughly. Use a fan for faster dry times.

Step 3: Lightly sand the surface with 220 Grit sandpaper after each coat.

Step 4: Apply the next coat of gesso, changing the direction of your stroke 90 degrees with each layer.

* For best results repeat steps 1-4 at least 4-6 times.

**Tip: You can tint your Gesso with acrylic colors if you want your base color to not be white. See photo for example of a pink gesso.

Step 2: Applying Interior Layers of Paint

After you prep your panels with 4-6 coats of gesso, then you are ready to start layering your interior colors.

There is no prescription for this as there are many great ways to get interesting results. I will discuss 2 methods that worked well for me.

Method 1: Spray paint or Airbrush

This approach can give you nice soft gradients of color with smooth transitions. I prefer to use Montana Gold acrylic spray paint as it comes in great colors.

I also add a couple of thin separation layers of acrylic matt medium to seal in the spray paint or layer multiple colors one over the other.

Method 2: Acrylic Paint Mediums + Inks

As you see in images 3, 4 & 5 , I experimented with layering Acrylic paint by hand as well as poring tinted Matt Medium for texture and variety. The nice thing about this method is that I could be very loose with my approach and play with textures and effects knowing that the top "darkest" layer and subsequent etching will give the work structure while the "painterly" marks underneath will provide a nice playful balance in the image.

* Wear proper safety gear when working with chemicals! Gloves, safety glasses and VOC respirator

Step 3: Acrylic Ground and Charcoal Top Layer

Once you finish layering your interior colors you are ready to apply a top coat of charcoal.

To prep the surface so it takes on charcoal use Golden brand Pastel Ground (pictured) applying 2-3 thin coats with a foam brush. This product has a fine pumice mixed into the base acrylic medium and therefore when dry gives the "drawing" surface" a nice tooth which allows better adhesion for the loose pigment in charcoal + pastels.

*Tip: Golden's instruction on their Pastel Ground container recommends to thin with water up to 40% I found this to be way too thin... so I use a damp foam brush and spread well or add 5%-10% water max. -- The only drawback to layering the pastel ground on thick is that its not 100% transparent, and dries with some opacity, thus the more one adds the more it dries with a filmy white opacity.

Step 1: As before apply pastel ground with a foam brush, using even strokes and allowing each layer to fully dry before applying the next one.

Step 2: Apply Charcoal or Pastels

When the second pastel ground layer is fully dry, I use soft compressed charcoal or Sennelier pastels for colors.

Put on gloves and rub the pigment into the surface by hand until the surface has a smooth velvety look, i like to buff it in making sure I have covered any small light spots showing through.

Step 4: Etching or Rastering With a Laser Cutter

Now the panel is ready to etch!

Prepping Files: Most laser cutters are very user friendly, they can input most image files into raster mode, JPGS, BMP, PDF's work well, just remember the laser cutter rasters essentially in Bitmaps so using a grayscale image is best. Also if you top layer is black, you will need to inverse the image in Photoshop or another image software so the etching looks correct.

Exporting Files: See your local laser cutter machine manual for exact output settings, becuase each machine and specific material will be different. Here, at Pier 9, I used a 75 watt and also several 120 Watt Laser Epilog EXT 24 x 36" Lasers.

My most frequently used settings were:

Raster Settings at 300 DPI, Power 33-51%, Speed 100%

The file can be opened in Illustrator, hit print, select laser, hit settings adjust all required settings, hit done, if all looks correct hit print, and the file will be on the machine.

Panel in Laser Set Up: Place panel into the laser cutter, adjust focus and height. Make sure vents are on and all is in order and now you are ready to hit GO! Best of luck!

*Experiments: You can try layering dark colors first and end with your top layer as light/white, then you will NOT need to inverse the image for correct output. Have fun playing around, the possibilities are endless!

Photo Examples above:
1. Source image

2. Etch file

3-5. Physical etchings / final outputs, (iterated to test a variety of surface preparations and techniques)

6-7. Multi layer etch and the great detail and textures achieved through this process.

8. The final image shows that each layer takes 45-75 minutes to complete.


If you wish to see process videos etc, I discuss this in greater detail in my Pier 9 artist lecture