depends on what you are doing to the glass. how much depth you want to achive, or scuplting you want simple designs with not to small details will work with the 3-4mil regular letter/graphic grade. masking tape low tack type will work for the edging around the artwork. duct tape works also for deeper blasts. you can also use 10-15 mil plastic sheeting for the surrounding area. contractor grade garbage bags will also work. the larger the blast media the greater the CFM of air the deeper the etch the more the substrate cost THE HEAVIER THE RESIST is a good rule of thumb PTSideshows law #23,879 Also don't forget to cover all exposed sides and edges of the substrate with brown paper bags/newspaper or plastic if it is the blast cabinet or if you are doing it in free air. Because you will scratch or damage the surface were you don't want it. The more aggressive the tack of your tape the more glue you will have to clean off after law #10 when you put the resist on the glass make sure you are using an alcohol based glass cleaner. use your finger work press all the edges of the artwork done so you can feel the bubbles. using a tool doesn't make it. And as with all bubbles they will pop. law# 234. Hope this helps.
------------------ PTSideshow been there, probally done that.
