Grease lining was a 1903 revelation that Wood stumbled upon one day while observing the behaviour of salmon and their disinterest to the deeply sunk fly.
Across the world, anglers actively used water-absorbing lines and heavily gauged hooks with the desire to fish their flies deep in the water column.
Mr. Wood soon perfected and popularized a revolutionary change. He learned that if he could coat the material of the line in a substance that would stay afloat, he could then swing his fly in a subsurface and somewhat drag-free presentation.
At the time, the best flotation materials were variations of grease – mucilin, lanolin, and animal fat were all thought to be suitable.
As I personally own and fish a silk line on my single-hand rod, it is in my experience that silk lines cast as seamlessly and effortless as the fly lines of today.
But maintenance can take its toll on the most patient of anglers. I know that for me, having to remove the line from the reel, dry itout overnight, restring it in the morning, grease it, apply felt, cotton, paper towel, stay busy until it dries, fish for four hours, and then have to do it all again… basically ensures only occasional use.