Win or Fail: DIY Sharpie Coasters

I think this tutorial is at least as old as Pinterest, but does it works?

I decided to give it a try when my parents discovered a box of extra white bathroom tiles from the renovation... 21 years ago!

I bought a pack of different colour Sharpies, very excited. I can't remember which tutorial I followed, but it might have looked like this one.  The result was very far from all the pictures I saw as you can see. I just saw one tutorial mentioning 99% Isopropyl Alcohol, I used 70%. Can this be the issue?

The disappointing result.

I bit the bullet and bought alcohol inks (Piñata and Brea Reese) and the result was way better.

To me, the Sharpie tutorial is a big...