Trying 4mm glass for the first time today. It seems more SUBSTANTIAL than 3mm and much less likely to break. I like the thicker glass so far. After I wash dry and varnish the plate, I will see how the extra 1mm feels when I look through three glass to the image captured inside. If that look pleases the. I will go to 4mm for all the format sizes I use. The 35x35 inch camera might even require 5mm glass!!
