The two main boards used in bookbinding are Grey board and Mill board. There are a few differences between them and each has their benefits and drawbacks depending on the project.
The most important thing to remember is that your board is used to create the case which will protect your pages. So, the content of your text block will help determine which type and weight of board is the most relevant.
The bigger and thicker the text block the heavier/thicker the book boards should be.
For instance, an A6 single section notebook could use 1.5mm grey board and an A4 photo album could use a 3mm grey board.
Mill board is denser and acid free so is often used when the content is more precious, for example you might use 1mm Mill board to house an old document or 3mm Mill board for a very large volume.
For design bindings most binders would use Mill board and often laminate different thicknesses to create the optimal density for the binding.
Here is a summary of the qualities of each type of board:
Grey board (aka Dutch grey, unlined grey or book board)
- Relatively cheap
- Made from recycled paper
- Fairly easy to cut
- Comes in various thicknesses from <1mm -3mm (750 – 2950microns)
- Not acid free
- Not very dense (can split or feather on edges)
Mill board (or Gemini board or elephant board (might be grey, dark grey or green))
- More expensive
- Very dense and strong
- Harder to cut
- Comes in various thickness 1mm – 2.8mm
- Acid free