Sheila has asked What zentangles are and what they are made of.
All a zentangle is, is a doodle! I do mine with a Staedtler triplus fineliner. They have a 0.3mm tip, so they give a very fine clear line. All my zentangles, so far I have done on A3 photocopy paper. I've just started one in an A3 sketch book.
I start with a simple shape like a circle or rough square and then section that off with flowing lines. Then I fill the created smaller shapes with doodles. I just relax and go with the flow.
This is a zentangle as a WIP.
I hope this helps Sheila!