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* This section published courtesy of Norm Dobbins
One of the most important decisions to be made in glass etching is which resist to use for a specific job. What you are looking for is the least expensive resist that is adequate for the job at hand. Controlling costs is essential for making a profit, but you can go overboard.
In your zeal to keep costs low, if you use a resist that is too thin, you run the risk of ruining the project if the resist blasts off before the project is finished. This means you will have to start over after you put in all the time necessary to transfer the design to the resist and cut the design out for blasting. The wasted time will cost you much more than better resist would have in the first place.
If you always go for overkill and use only the heaviest resists available, you will not only be wasting money but it will be much harder to get the special effects you want. Since the heavier resists are thicker it is difficult cutting and blasting in fine detail. It is also more difficult to achieve subtle changes in depth when carving in small areas or subtle changes in gray scale when shading.
Consequently, it is best for the quality of your etching as well as the quantity on your bottom line to use the proper resist for the job. Know which resists are available and how to use each one of them to best advantage.
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Resist Selection Table
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Resist Type
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Thickness
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Uses
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Characteristics
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Clear vinyl
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4 mil
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shading to surface etching
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Adequate only for light blasting, somewhat difficult to remove from large areas of glass without tearing.
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Clear vinyl
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8 mil
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shading, surface etching, light carving
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Good margin of safety for all types of blasting through light carving; does not tear when removed from large pieces of glass.
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Clear vinyl
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11 mil
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light to medium heavy carving
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Somewhat difficult to cut because of thickness, good for correcting mistakes in carved areas.
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Opaque vinyl
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4 mil white
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shading to surface etching
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Adequate for light blasting on smaller pieces. Difficult to remove from larger pieces without tearing out in strips.
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Opaque vinyl
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6-8 mil white
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shading to light carving
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Inexpensive multi-purpose resist, easy to remove from glass in large or small areas.
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Opaque vinyl
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10-15 mil white or black
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medium carving
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Thick, hard, difficult to cut. Good for medium carving.
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Rubber
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11 mil green
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surface etching to medium carving
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Very easy to cut, especially fine detail; very tough for its thickness. Can be stretched around curved objects.
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Rubber
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18 mil tan
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light to heavy carving
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Very easy to cut, good for fine detail; best overall for general carving. Can be used on metal or stone. Good on curved objects.
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Rubber
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30 mil tan
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medium to heavy carving
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Easy to cut, moderately good for fine detail, tough; can also be used on wood, stone or metal.
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Rubber
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45 mil green or tan
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heavy carving
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Easy to cut, difficult for fine detail, very tough; also used for wood, metal, stone.
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Types of Resist
Clear resists can be used for surface etching when you want to avoid the step of tracing the pattern onto the resist on the glass prior to cutting out the pattern. Just place the pattern under the glass with the resist on it and cut the pattern, looking through the resist and the glass to see the pattern underneath. Although this technique can save a lot of time, many don't like it because it is difficult to see when your cut lines are properly aligned over the pattern. The reason it is not used for shading or carving is that in both of those techniques, you peel the resist in stages an blast each stage separately. By the time you get to teh third or fourth stage, the discoloration caused by the abrasive on the resist has partially obliterated the cut lines, making it very difficult to see just where the pattern has been cut. When you can't see the cut lines on the pattern, it is nearly impossible to peel the resist out properly. Opaque resist is much better for stage blasting because the trace lines show up much better after the blasting has been started.
The 4-mil clear resist is used frequently to protect the back of a sheet of glass from being scratched during handling. Thicker clear resist is used in correcting mistakes by re-applying it to a blasted area. Since you can see the blasted pattern through the resist, it is easy to see where to re-cut the pattern areas to be corrected and to blast the affected area again.
Rubber resists are more resilient and easier to cut than vinyl resists. They are also much more resistant to failure from excess heat generated by the friction of blasting. These factors make them better resists overall than vinyl materials. However, the rubber resists are considerably more expensive and are not available in the thinner sizes. Therefore, vinyl resists are used much more for blasting large areas and where the etching techniques don't involve very deep blasting. Any time are etching a particularly expensive piece of glass (such as crystal or thick plate glass), always use at least the 18-mil rubber resist to guarantee that the resist won't peel up during the blasting and ruin the glass.
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About Contact Paper
Many people start out etching glass using contact paper as a resist. This is a 5-mil think vinyl which is used as a shelf liner for kitchen cabinets and it works acceptably well for shading or for surface etching except for one major drawback. It uses a permanent type of adhesive which stays on the glass when the contact paper itself is removed. The longer the material is on the glass before it is removed, the worse the problem is. On small pieces of glass, it is not too difficult to clean off after etching is done. On larger pieces, the cleaning process can take as long as the actual etching process. The benefit of contact paper is that it is very cheap. You may want to try it out if you are on a limited budget and if you can complete the entire process in one day or less.
Conclusions
When you are just starting out, you may not know what type of etching you will be doing most, and you may not know which resists to stock. Four types of resist will cover almost anything that comes up.
A 50 yard roll of 6-mil white is essential because it is an all around resist that can be used for shading, surface etching and light carving. It is very inexpensive and you will probably be using more of this resist than any other. A 10 yard roll of 11-mil green rubber resist will take care of most carving in 1/4" plate glass or wherever you need especially fine detail.
You will also need a 10 yard roll of 18-mil tan rubber resist for deep carving in 1/4" glass or most carving in 3/8", 1/2" or 3/4" glass. For very deep carving in 1/2" or 3/4" glass, you can double the layer the 18-mil resist. It is a little more expensive to do that than use the 30 or 45-mil resist, but you won't need to do it very often.
The last resist you will need is the 8 mil clear, which you will use for correcting mistakes and possibly for surface etching on small projects. About 10 yards is a good starting amount.
As you do more and more etching, you will develop your own favorite resists for your particular technique and for the type of jobs you are doing. Just remember, using the right resist for the job will always save you money and time and will give you much higher quality results.
© Norm Dobbins
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