I always used silkspan (up until the good stuff was mostly gone) because it finished the lightest of most coverings except jap tissue and was far easier to use than silk. As mentioned the cost was another factor both in silk and the extra dope it required to fill. No doubt you can get a great finish on silk too. I recently covered a new one in silk. It went over weight pretty fast at 700 sq. in. and hangs on the wall to keep the house firmly down on the foundation. I'm now fully sheeting everything and coming out lighter. Silk is great for smaller airplanes, trainer types and certainly old time projects. I recently built a few nostalgia combat airplanes, Sneekers, Big Iron and they are silked for durability.
Dave
I cut a sq. yard of silk and I cut a sq. yard of silk span for a weight test.
The silk span weighed in at 11 grams and the silk at 14 grams. WOW! what a difference.
Having used both silk and silk span, for me anyway, I like the silk better for many reasons.
I find dope fills the weave on the silk with less coats than silk span. But that's me.
Obvious differences from person to person because of many reasons. The percentage of the thinning, type of brush, application, the method the modeler uses to apply the dope, i.e., amount of pressure and brush movement, fully loaded or not.
Terry, you're new so you haven't seen these models. All have silk span covering. The wing to my Gee Bee Z has silk span. I'm considering recovering it with silk. This model, The ARGO 2 was covered in silk span, I recovered it with silk. Finished weight was just under 55 ounces.
Dave, I remember you saying you experienced "cracking" in the open bays with silk span. Did you ever draw a conclusion or reason as to why this occurred?