I put the pre felt on a layer of bubble wrap and put a hand-painted or digitally printed thin silk fabric on it. Then I wet these 2 layers with warm water and soap and press the whole gently together, making the wool and the silk "stick" together. The bubble plastic with the wool and silk I then roll together around a long roll of foam. By rolling the whole thing for 3x 15 minutes and unrolling it inbetween and working it by hand, the fibers of the wool pass through the holes of the silk. Wool shrinks and takes the silk along, as it were, so that the wool and silk are combined into a beautiful wool / silk fabric.
You can imagine that the choice of the color of the pre felted wool influences the end result, because the fiber goes through the silk. In order to be able to predict a little bit what the end result will look like, I have done tests with pieces of painted silk on different colors of wool. On the pictures you can see what that looks like.
The end result is super useful. Also for workshops to show participants what result will be of a certain color combination of wool with silk.