This lesson is from a tutorial that was done years ago by Antares
Colour filling is a term used within the awards and engraving industry to describe a variety of techniques used to add colour or contrast to engraving. Even though there are a wide variety of engraving materials available that come in a multitude of colours, thickness and finishes, there are often times when it is desirable to colour the engraving to make it stand out or enhance the overall appearance of the product.
There are three basic processes or applications that fall under the category of colour filling. The most common, which is used to blacken engraving on brass and aluminium, isn’t really ‘filling” at all. It is actually an oxidization process done with a mild acid which blackens the exposed metal upon contact. Since this oxidizing process isn’t selective as to where it works, it can only be used on metals that have some kind of coating that is removed in the engraving process.
For example, the commercially prepared brass common to the industry is coated with lacquer or some other durable finish. Aluminium can be coated in a similar manner or it can be anodized. Anodizing is an electro-chemical process that seals the surface of the metal and prevents natural oxidization. When we remove any of these finishes with a diamond graver, burnisher or a rotary cutter, exposed areas can be blackened with the oxidizing solution without having it affect the rest of the plate.
Oxidizers are available for both brass and aluminium from a variety of sources. They are all reasonably effective and the only consideration is that it is fresh and free of contaminants. While most oxidizers are supplied with a dauber, this may not be the best way to apply it since you would be continually putting the dirty applicator back into the clean solution. A better method is to use cotton swabs and discard them after each use.
It is equally important that the engraving be clean and free of any oil or even finger prints. Since metal experiences natural oxidization when exposed to the air, it’s a good idea to oxidize it soon after it’s engraved so the full effect of the oxidizer is achieved.
On small plates, apply the oxidizer liberally to all of the engraving. It sometimes helps to actually ‘scrub’ it into the letters with your swab. Allow the engraving to darken and, when the desired effect is achieved, rinse the plate with water. Rinsing will dilute the acid and stop the oxidizing process. If the oxidizer is left on too long, the process will continue and the blackened areas may turn grey and chalky and even flake out of the engraving.
After rinsing, blot the plate softly with a cloth or paper towel – don’t wipe it because it is possible to rub the black out of the letters. You can make a final clean-up after the plate has dried. If there are any areas that didn’t take, you can go back and repeat the process.
No matter how good a job you do, oxidized engraving will have a dull, lustrous appearance. It is possible to enhance the appearance by applying silicones, spray lubricants and even furniture polish to the plate. While these methods tend to darken and add gloss to the lettering, their effects usually diminish in a relatively short time.
Actual colour filling where a fill material is applied into the engraving can only be done on rotary engraved plates and is usually done with paint or a paint stick. A paint stick looks like a large crayon, is available in a variety of colours, and is simple to use. First, shave the end of the stick with a knife or razor blade to remove any skin that has formed. Then, rub the stick back and forth across the engraving until the letters are filled and then wipe off the excess with a cloth or paper towel.
On some surfaces, the paint stick will leave an oily residue that can stain the surface of the plate. Sometimes alcohol or paint thinner is effective in removing this film, but the easiest way to completely clean the plate is to allow it to dry over night and then wash it using warm water and a nonabrasive cleanser such as Bon Ami. While this method of filling is easy and reasonably durable, it never gets completely hard and doesn’t offer the smooth, glossy appearance that paint does.
Paint filling, while a little more difficult than the other methods, offers the broadest number of options in terms of materials, colours 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 such as flexible engraving stock and other materials that may be affected by caustic solvents, use latex or acrylic paints and water or alcohol for clean-up. Other than this, the procedure is essentially the same for both. In addition to the paint, you’ll need an inexpensive brush, an old phone book and some pieces of stiff paper or cardboard (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 114″ 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.
The consistency of the paint should be such that it is thin enough to flow freely, but thick enough that it doesn’t allow the cutter marks to show through after it has dried. Using the brush, apply the paint liberally so that the engraving is completely filled. Immediately after filling, hold one of the cardboard pieces so that its straight edge rests against the plate and scrape off the excess paint leaving just a thin film. Allow the plate to dry for several minutes until the paint has started to setup and the surface can be wiped without disturbing the paint in the engraving. The time varies depending on the paint being used, but 5 to I 0 minutes would be a good starting point.
The next step is the initial clean-up of the surface of the plate. Wrap two or three thickness of a lint-free cloth tightly around a wood or plastic block and dampen it with thinner. Wipe the surface of the plate lightly, in one direction, until the paint residue is removed. On small plates, an easier method of cleaning is to wipe the plate across the cloth. A widely-used and effective alternative to the cloth method is to use pages from a telephone book. Their texture allows them to absorb the thinner and any problem with lint is virtually eliminated.
There are two key things to remember that can mean the difference between success and failure. One is not to use too much thinner. If the cloth or paper is too wet, thinner will seep into the engraving and attack the paint ruining the appearance. Secondly, when wiping, do it lightly so as not to allow the cloth to come in contact with the paint in the characters.
After the plate has been wiped clean, there may still be a haze that requires some additional cleaning. It is best to allow the plate to dry, preferably overnight, and then do the final clean-up when the paint in the characters has completely set. You may want to use soap and water or a cleaner that will remove any oily residue left by the paint and thinner.
When filling larger letters, it is possible to eliminate most, if not all, of the cleaning and wiping by using an applicator that allows you to apply the paint directly into the engraving. Some systems utilize small plastic squeeze bottles with needle-like nozzles while others are more elaborate mechanical dispensing systems. With either method, paint is squeezed through the fine nozzle directly into the character. With a little practice, you can become adept enough to eliminate the need for major clean-up.
Some of the best sources for small amounts of paint in a rainbow of colours 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 effect the plastic.
If you use your imagination, you can create some very dramatic effects through colour filling. There are other ways to add colour and create dramatic effects on nameplates and signage. You can spray paint a clear acrylic plate one colour, engrave through the painted surface and fill the engraving another colour. You will be able to produce signage to match a company’s corporate colours or co-ordinate with office decor.
There are also commercially available engraving materials that are made for reverse engraving and colour filling, These materials have a clear face and a coloured background. Merely engrave through the rear surface, apply paint to the engraved area and you have a sign with a coloured background and contrasting letters.
There is no questions that colour filling requires extra time and effort, but once you’ve mastered the techniques involved, you’ll be able to enhance and expand the products and services you offer.