Okay, I shared about paper weight last week. Now let’s talk about paper types.
Cate, you were especially interested in the differences between Bristol and Vellum so I’ll start there.
Bristol is a plied paper, hence packaging labels stating 2-ply, 3-ply or more. That means rather than being made to a certain thickness direct from the paper pulp, they laminate multiple sheets together. This gives you two right-side faces of the same properties to work on. Most paper has a right side and wrong side. The difference is often really subtle and hard to distinguish as it might just be the difference of what side was in contact with rollers. Alternately, some papers come with two distinctly different textures. Bristol is primarily used for illustration purposes so is smooth for better reproduction.
Now, to complicate the answer to your question, Bristol is usually labeled as “Smooth” or “Vellum.” Smooth Bristol is meant primarily for ink in the form of pens and/or markers. It is so smooth that laying down other media like pencils is somewhat difficult. I can attest to this a bit since my DIY tiles are Smooth 2-Ply Bristol. I sometimes have difficulty with blending my shading. The smoothness acts like super smooth sandpaper to my blending stub bringing it to a near polish so I have to rough it up with a sandpaper block often.
Vellum Bristol has some tooth to it, though markedly less than the official Zentangle tiles. It is a more of an all-around dry media illustration paper. It takes ink, marker, graphite and colored pencils. Some illustrators feel there is slight bleed/feathering with their ink pens on Vellum Bristol. I suspect it is relatively minor or they wouldn’t be rated for use with pen. Plus, the official tiles are watercolor paper and thus likely more prone to feathering. Unless you are planning on digitizing and reproducing your work I suspect Vellum Bristol will meet your paper desires of heavy and smooth with ease of shading the best.
One thing to note – vellum also exists that is not at all like Bristol. That vellum is a semi-transparent parchment used for Pergamano (another fun obsession).When I practiced Pergamano it took more work to source that vellum so you shouldn’t run into problems of mixing the two up. It is good to know it exists just in case.
Bristol of either classification will not hold up terribly well to media any wetter than markers, regardless of the ply or weight. So Bristol is not a one paper suits all answer if you fully embrace the watercolor pencils or other wet media. While I did a light wash on some, it buckled horribly (I actually ironed it and it still doesn’t lay flat). The wash took a bit to sink in causing it to pool which reduced control (not an issue if you are using a wash to create your “string” but problematic if you are coloring an already drawn tangle).
If you would get into the wetter media at some point, I suspect you’ll want separate journals to work in. Hot press watercolor paper is the smoothest, but it isn’t bound into sketchbooks or journals. The texture of cold press watercolor papers is part of what gives watercolors their luminosity so hot press is mostly used for more opaque work. I’ll dive a bit into other papers at a later date, but suspect this is more than enough info to digest for the moment.