I made one a long time ago (10+ years ago) from a fresh corn cob. Worked OK, but I think it does better with dried corn on the cob, and small ears at that. I live in a heavy agricultural area of the US and there are wide ranges of corn cob sizes depending on the type and purpose. Larger ears will give you nothing but pith on a pen. Some feed supply stores have smaller dried corn for animal feed. Those are good (here in the States). For my fresh corn cob, I microwaved it for about 20 seconds and let it set for about 5 to 10 minutes; repeat that about 6 to 10 times. let it set a day or two and try it again in the microwave. DON"T run it more than 20 seconds or it will BURN.
Back in the early day, people would soak CA all inside and around the cob to make it into a pen. Turn it down a little and soak more CA onto and in it. Repeat. I think today, most would soak it is stabilizer and pull a vacuum (on a dry cob).