Ive done some custom engraving on a few AR builds, and ive found the best way is a technique called paint filling. Heres how to do it
Paint filling offers the broadest number of options in terms of materials, colors, and applications. For metals and rigid plastics (phenolics and acrylics), it is best to use a fast-drying, oil based enamel and mineral spirits for the cleaning operation. On soft plastics and other materials that may be affected by caustic solvents, use latex or acrylic paints and water or alcohol for clean-up. In addition to the paint, all you’ll need are an inexpensive brush, an old phone book, and some pieces of stiff paper about the size and weight of a business card.
The engraving should be smooth, free of burrs, and have sufficient depth to hold the paint. As a rule of thumb, with characters up to 1/4" high, engrave to a depth of .010" - .012". On larger characters, it is advisable to go .015" - .020" deep depending on the line width and filling technique used.
Brush the paint on liberally so that it is thick enough to hide the cutter marks after drying. Immediately after filling, hold one edge of the cardboard so that its straight edge rests against the plate and scrape off the excess paint, leaving just a thin film.
Wait about 5-10 minutes until the paint has started to set-up before starting the clean-up process.
To clean the surface of the plate, wrap two or three thicknesses of a lint-free cloth tightly around a wood or plastic block and dampen it with thinner—don’t use too much or the thinner will remove the paint in the engraving.
Wipe the surface of the plate lightly in one direction until the paint residue is removed (pressing too hard might wipe the paint out of the characters). Pages of a telephone book are often used instead of cloth. Their texture allows them to absorb the thinner, and they don’t give off lint.
It is best to allow the plate to dry, preferably overnight, and then to do the final clean-up when the paint in the characters has completely set. Use soap and water or a cleaner that will remove any oily residue left by the paint and thinner.
Some systems utilize small plastic squeeze bottles with needle-like nozzles or other more elaborate mechanical dispensing systems which eliminate most, if not all of the cleaning.
Some of the best sources for small amounts of paint in a rainbow of colors are touch-up paint from the automotive store and paint sold at hobby and art supply stores. Always test the paint before applying it to your finished engraving to make sure it will not affect the plastic.
Thank you very much for the info. I am more confident I can handle this myself now.:thumbsup:
Do you happen to know if the colored anodizing on the BT products will be unharmed by contact with thinner?
If not I can ask the folks at BT.
No worries my friend. They should not. I anodized my AR lowers myself and they held up just fine. As fine as a company as BT is, i suspect their products would most definitely hold up to it. Essentially all anodizing is is dyeing the oxidation layer of Aluminum. This oxide layer is Extremely tough.