I wanted to color the labels on an acrylic box for a Raspberry Pi enclosure with a paint. This method uses a powder which is etched into the laser engraving. The powder used is called LaserDarc. I bought a sample of 3 colors for around $70.
The Raspberry Pi enclosure pattern was from Thingiverse.
The laser used was the Trotec Speedy 300 at my local Techshop. This instructable assumes you already know how to cut and etch acrylic on your laser.
Step 1: Etching the Acrylic Plastic
The first step is to etch the acrylic. I used the default setting for etching but ran the job 3 times to get enough depth to hold the paint.
Step 2: Loading the Paint Powder
This is the messy part. Remove acrylic from laser. Over some cardboard, or preferably in a cake pan, fill the etching with the colored powder. Try to brush some into every nook and cranny.
Step 3: Brush Off the Excess Powder
Using a straight edge ( I used a credit card) brush off the excess powder. The excess powder can be placed back into container.
Step 4: Re-engrave Your Image
Place the acrylic back into the laser. Run the engraver at low power and high speed. I followed the directions included with the powder at 20% power and 80% speed.
Step 5: Repeat As Necessary
If you engraved your acrylic deep enough and got enough powder into the etching you are almost there. If not just repeat applying the powder and etching until you are satisfied with the results. Some trial and error will be involved.
Step 6: Cut the Acrylic
After you are satisfied with paint process you can cut your pieces out. This was done last so that the etching would be over the exact same spot as the process of remove, paint and etch is repeated. These pieces here still need a little cleaning.