Advanced Engraving Techniques: Reverse Engraving
I chose to title this chapter Advanced Engraving Techniques to separate its contents from the day-to-day flat work engraving we find in most shops. If you find yourself working in the plaque or trophy world most of the time, then the previous look at the three engraving techniques is not new to you. If you want to provide a fresh look for your customers or simply experiment with some new products then this chapter is for you.
The range of products that could be covered in this chapter is endless. To properly explore each one is almost impossible. I have attempted to address some of the most common techniques or products faced by engravers. Once you gain some experience you will be able to adapt many of the techniques listed below to the thousands of unique engravable products.
Engraving in the reverse is not unlike engraving in the first surface. Somehow a myth has been attached to this technique. If you have engraving software, you probably have the tools to engrave in the reverse. The only difference from first surface engraving is that the job is mirrored horizontally, probably engraves from right to left, and the material you use is engraved from its back side. Materials specially designed for this application are usually 2-ply with a thick clear surface as viewed from the front and a thin colored layer on the back. When the engraving is completed, you will be able to see completely through the plate.
Although any flexible engraving tool may be used, you will want to be sure that the tool is sharp. A good clean cut will eliminate extra cleanup and chip removal later. Smooth characters free of burrs will fill much easier. If engraving acrylic, be sure to use a tool designed for that specific material.
If you plan to engrave mostly text, you may want to try a ball-nose cutter with a single stoke font. The effects can be interesting, giving an almost 3-D appearance when color filled.
One of the problems you may have after engraving is that you will see the tool path very clearly. You may be surprised to find that the engraved area is very hazy and the tool marks will show. This is caused by the rub or cut made by the tool. Before paint filling, spray the engraved area with clear acrylic paint. This will smooth the cut marks a bit and remove the haze. If you don't take this extra step, you may notice that the paint color will be dull and less vibrant.
In most instances, the only consideration in the set-up of a reversed engraved job is the orientation of the plate when mounted on the engraving table. To ensure that the left and right margins are correct when engraved, you will need to take extra caution when sizing the plate or cutting it. You may want to shear your plates face down so that all of your calculations for size are correct when engraved. When you place the plate on the engraving table, be sure to turn it face down. Remember that you are only mirroring the plate and that the top of the plate must still remain at the top of the engraving table, and you will still use the upper left corner as home position. I recommend that you leave the protective plastic coating (found on the front of the plate) on until you have finished engraving or until any color filling has been completed. This will protect the front of the plate during handling.
Your engraving software should allow you to flip the plate or layout in the software and view it as it will actually be engraved. Don't panic when you actually start the job. The engraving head will move to the top right hand corner of the plate to start the engraving.
Unless you are doing reverse engraving in a clear piece of acrylic, you do not need to protect the back of the plate against the scratching of the nosecone. A vacuum system will work well with this application.
In most reverse engraved applications, we will be "paint filling" the characters. You will need to engrave to a depth of .010" - .015" for characters up to a 1/4" high. For larger height letters plan to cut as deep as .020".
Color filling is a term used by all engravers to describe several techniques to add color or contrast to engraving. Although there are a wide variety of engraving materials to choose from, we sometimes cannot find the exact color we want. If we are trying to architecturally match a color and the engraving stock is not available, we may be able to engrave a neutral material and color fill with PMS matched paints. Although oxidizing (discussed in chapter 7) is a form of color filling, most engravers feel that the use of paint is the true definition. Here are two methods you can choose from:
Paint Sticks - Paint sticks look much like an adult size crayon. They are usually found in primary colors and are easy to use. Paint sticks are great for small areas that need to be filled. I do not recommend their use when coloring front engraved plates. These are great for the back of reversed engraved tags or small plates.
Paint sticks tend to dry out from storage and we want to get down to the soft area of the stick for painting. The first step is to remove the dry paint skin that has formed. Use a utility knife to cut away the skin. Paint sticks can be very messy, so be prepared by having an old rag handy. Simply rub the paint stick over the engraved area. The paint will be forced into the material and the excess can be buffed off. The plate should then be allowed to dry overnight before use. If the paint has smeared into unwanted areas a little paint thinner or alcohol may be used for clean up.
The areas painted will never completely dry, so take special care if you plan to use this method on name badges or any surface that can come in contact with clothing etc. 1 like to mount the badge onto another thin plate to protect clothing.
Paint sticks are very inexpensive and are great for the occasional job. Don't try these with large characters or areas, the look will be dull and getting a complete fill will be difficult.
Paint Filling - Paint filling requires a little bit of technique and sometimes a great deal of clean up. When I speak to engravers about paint filling, they usually cringe. Most have tried it under duress and have realized poor results. One of the reasons why the first experience is so painful is that they have the wrong expectation about the work involved.
For metals that are first surface engraved, fast drying enamels will work. Have paint thinner handy for clean up. If you fill flexible engraving stock, use acrylic or latex paint. Always check the material manufacturer's specification firsts. Some plastics may be affected by the paint, the clean up solvents, or both.
I have seen paint applied with a brush, roller, squeeze bottle, squeegee and syringe. To limit the need for clean up, when filling large, front engraved letters, I recommend the syringe. The paint must be a consistency that allows it to wick up the characters but yet thick enough so that it will dry overnight. The paint should puddle in the letter and also wick up the sides. The finish should be smooth and glossy. Before the paint is dry, carefully wipe off the excess or overruns. A particularly interesting trick is to use an old phone book soaked in solvent to remove the excess paint. Place the plate face down on one of the soaked pages and wipe in across the page in one direction. Keep turning the pages, repeating the process until all of the excess paint on the surface is removed, leaving the paint deep in the engraving remaining.
Cloth can be used in the same fashion but the paint must be relatively dry. If the paint is wet, lint from the cloth will stick to the engraved areas. A substitute I have used is a coffee filter. An engraver told this trick to me. This method of paint clean up works great (I'm sorry I cannot remember the person who passed this tip along, but thank-you anyway).
Keep the amount of thinner to a minimum so that the cloth or coffee filter is not wet. If too much thinner is used it will break down the paint and you will need to start the whole process over again.
If the characters are small, you may want to apply paint over the entire surface, squeegee off the excess and clean up using the phone book method.
For reverse engraved plates, a simple approach that can be used for work requiring a single color is to use spray paint. Not many people would agree with this but I have found it very effective. Check with the manufacturer of the material to determine the best paint for the material. I have used Krylon spray and been very happy with the results. Remember to place tape or a protective barrier around the plate edge to avoid over spray. I usually do two coats. One I will do from the direction of the plate top and the other from the bottom. This allows me to get the coverage I need on the sides of the characters. Spraying from directly over the plate does not get the paint on the sides of the letters. Try holding the can a few inches away from the area and at an angle to the plate.
Regardless of the paint or color filling method used, you will find a completely new and dramatic look can be achieved. The colors can be limitless. Don't wait too long to try this. Once you've settled on a process that you are comfortable with, you will want to use it on many more products to expand your offering.