I have found that using a soldering iron on Tyvek gives me the ability to accurately create small holes. The resulting lace-like effects also give a very biological appearance too.
Colouring and layering
In some of the examples I have coloured the Tyvek before burning the holes. In some instances I used yellow inktense pencils. Whilst others I coloured with a black sharpie. Other coloured surfaces are visible through the lace-like Tyvek. Layering pieces creates some interesting visual effects.
In order to create the larger, more defined holes and shapes I had to use a different approach from just pushing the soldering iron tip into the paper. I drew around the inside area of the hole I wanted using the very tip of the soldering iron. This allowed the central piece to be removed leaving the hole I required.
Bottom left is Tyvek with black marker one side before application of the soldering iron. Displayed white side up. The interesting black outline to the holes in one of the pieces are infact made up of melted Tyvek and black ink. It almost creates a 3D effect to the piece.
I could use these pieces in my collages easily enough and to good effect. However, I would also be interested in using them as collagraph pieces. It maybe that the results of inking give a much less intricate appearance as the ink will stay in the holes and they may actually hold too much ink resulting a very inky mess.
Another possibility would be to use them to create patterns in a soft ground on a plate. A number of pieces layered might produce an interesting result.