Understanding the Relationship Between Photoresist Film Thickness and Artwork

With over 35 years in the glass business, Ruth Dobbins offers experience in fused and cast glass, as well as in glass-etching techniques. Ruth holds a Master's Degree in Printmaking and Art History and has been a partner in a stained and fused glass wholesale supply company in Europe, which also placed great emphasis on a training program. For the past 20 years, she collaborated with her husband Norm Dobbins in commission work, writing books and creating videotapes on how-to techniques for glass etching. Ruth taught these techniques for 30 years in the U.S. and other countries. Ruth continues these venues by offering a complete training program at Aliento School in Santa Fe, New Mexico, and by teaching at various trade shows, including The Awards & Engraving Show. One-on-one training and consulting services are also offered. You can reach Ruth by email at ruth@etchmaster.com, by phone at 505-473-9203 and by fax at 505-473-9218. Check out the website at http://www.etchmaster.com

You will find out that photoresist films come in a couple of different thicknesses, usually 3 mil or 5 mil, on average. The thickness choice is governed by the substrate and/or depth you want to blast. If you want to blast on tile or stone, you want to select the thicker film. 

You cannot blast a line deeper than it is wide, which also affects stencil production in that if you have a fine line that is thinner than the film is thick, the line quality may not be equally good in all spots. In other words, the line may not materialize. 

Images that blast fine in a 3 mil film may not give you good results in a 5 mil film. The problem is that images usually do not have the same line quality overall. Any image should be examined closely; and when you detect line qualities that are too fine for a 5 mil film you need to create a copy of the image on the computer and increase the line width so it blasts well. 

—Ruth Dobbins, Professional Glass Consultant