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Etch Masters: Etching Marble Plaques

The next time a customer comes in to order a wall plaque for a commemorative occasion, try something different. Instead of offering the same old boring brass on walnut, offer the client a completely new approach to plaques. If you are abrasive etching glass awards, you already have the equipment and materials you need to etch on marble, and suppliers are offering marble plaque kits that have everything else you need. It is a simple matter to expand your offerings so your customers have something new to select from, and it will only cost you the price of stocking a few of the plaques in different sizes.

The plaques are available in several standard sizes like 6” x 9” and 8” x 10” and include a flat, polished piece of marble (usually green marble), a nicely finished wood frame and hardware for hanging the finished plaque on the wall. All you have to do is do the etching on the marble, right? Well, almost right.

It is pretty easy to do, but there are some definite considerations you will want to know about, to keep from ruining your projects. These are considerations that result from the differences in etching on glass versus an opaque substrate like marble. But let’s tackle the project from the beginning.

Since the marble frame covers part of the marble (usually about 1/4” to 3/8” all around the edge), be sure you make a template on your computer (within which to do your layout) that is smaller than the actual marble size. In addition to reducing the layout size by the dimension of the edge covered, also reduce it by another 1/4” or so all around, just so the text doesn’t get so close to the frame that it looks crowded. Some layouts will look best, of course, if you leave even more space.

In creating your layout, you will want to keep in mind that the beautiful matrix of veining and different colors that make marble so attractive actually make text etched into the marble very difficult to read. In addition, the carved marble will be somewhat “pebbly” looking, because the softer areas of the matrix carve deeper faster than the harder areas. (Glass doesn’t do this at all, being a perfectly homogenous mixture.) This also makes reading text more difficult.

This realization requires two different compensations in your project. First, avoid very small text. Do some samples on a piece of marble, using text of different sizes, just to see what you personally will want to recommend as a minimum size to your customers. Most people will want to make their minimum point size to be in the range of 18 to 20 points or larger. This consideration also applies to very thin lines and small dots or other elements. But even this won’t help if you don’t take the precaution in the second step!

No matter what size of text (and graphic elements) you use, the marble matrix will still interfere with clearly seeing what is engraved, unless you also color-fill the engraved elements. This is very easy to do, since it involves a simple procedure of spray painting the engraved elements, so they are a solid color (which stands out against the visually busy matrix). The most popular colors for this use are metallic colors—either gold, silver or copper. Other colors can also be used, but don’t stand out as much.

We say it is a simple procedure, though if you have never color-filled etched or carved glass, you may not have the slightest idea of how to do it. We are going to go through the basic etching procedure later, and we will give a description of the color-filling process when we get to that point.

After creating your layout, print it out on the same transparent or translucent material you use for creating masters for etching glass. This is specially treated transparency film (inkjet printers) or drafting film (laser printers) which takes a very dense, dark print that blocks light. In your darkroom area or other area where you process your photo resist for glass, cut a piece of photo resist that is at least 1/4” larger than the printed image all around. Lay the original printout face down onto the emulsion side of the photo-resist film, put it into your exposure unit, and roughly center the image on the photo resist.

Expose the resist for the prescribed amount of time, from 30 seconds to 2 minutes, according to the manufacturer’s instructions, and remove it from the exposure unit. Wash out the emulsion side of the photo resist with warm water until all the emulsion has been removed from the image area, then dry the photo resist. It is now ready to be applied to the marble or to be applied to silicone backing paper (to preserve the adhesive) for later use.

The entire process of exposing, washing out and drying the resist should take about 20 minutes for one piece, no matter how complicated or how large the etched areas are to be. However, if you have more than one piece to do, you can achieve a significant economy of scale by processing several pieces at once. For example, you can be washing out one image while another is exposing and another is in the drying oven. In this way, you can actually process from 6-8 images in 40 minutes, instead of only one in 20 minutes. The smaller the images are, the more you can process at one time, since you can gang your exposures with several at the same time if they are small enough to fit onto the exposure unit’s platen.

Keep in mind that since you are etching stone, you will want to go a bit deeper than you have to go if you are etching on glass. This will make the lettering and graphics stand out more and have a higher-quality look. This is even truer when the graphics are color-filled, and the extra depth makes color-filling easier. With color-filling, it will be obvious that the design is carved into the stone rather than being simply painted on the surface.

Because you are carving into the stone, you will be blasting for a longer time, at a higher pressure, so you should plan to use a thicker photo resist than you may be using on glass. We recommend at least a 5 or 6 mil thick resist for this. This gives you just enough extra margin of safety that you won’t have to worry that the centers of the letters will be coming off at any time.

So, when you are ready to carve the stone, remove the resist from the backing paper (or take it out of the dryer) and apply it to the polished surface. Take care to align the lettering parallel to the edges and center it between the sides. The easiest type of photo resist to use is one that is self adhesive, so you don’t have to apply adhesive separately. Squeegee the resist down to the surface, avoiding bubbles as much as possible, and remove the mylar cover sheet. Tape around all the edges of the resist with good quality masking tape about 1 1/2” wide, to protect exposed marble.

Put the marble into the blaster and blast evenly, until letters are about 1/32” deep or a little more. While you can blast whole words or even whole lines of text at one time with small letters, you’ll find it easier on the larger letters if you just blast one letter at a time until it is done. Then move on to the next letter.

When you are finished, double check for evenness and uniformity of depth. Now you are ready for color-filling. There are two approaches to this—spraying on the color while the resist is on or removing the resist and spraying. With the former approach, you have to remove the resist before the paint is completely cured or taking off the resist may lift and tear out some of the paint. This is tricky in smaller areas around and between the smaller letters, and resist pieces may drop into some of the still-tacky paint.

We find it easier to remove the resist first, then tape off the major areas that are not etched and spray the whole surface. Of course, the entire exposed marble gets painted this way, which scares most people. But it is a simple process to clean off the polished marble with a razor blade, while leaving the paint fill in the deeply carved areas of the design. This works if the marble (or whatever stone you are using) doesn’t have any cracks or voids in it. If it does, the paint gets down into those areas and is almost impossible to get out.

When you are finished with the color-filling, all that remains is to do the final cleaning of the surface and mount the marble into the frame. When cleaning, use alcohol-based window cleaner (most foaming window cleaners), and spray it onto the cleaning cloth or paper towel rather than onto the marble. If you spray onto the marble, you run the risk of saturating the painted areas and having the water get in under the paint. If it does, it can loosen the paint, and it will eventually come off.

With a little practice, you can create one of these etched marble plaques in about an hour, and it is a beautiful and unique alternative to the standard plaque. As such, it will bear a higher price, and there will be a substantial profit margin in it as well.

© 2007 Norm & Ruth Dobbins