Mountboard comes in various thicknesses, the standard and most common being between 1.4 and 1.5mm, but there are also boards available at (for example): 2mm, 2.2mm, 3mm, 3.5mm and the thickest at 4.1mm which is only available in white.
As with jumbo (large external) sized boards the colour choice decreases as the thickness increases. I find the metric measurement of mountboard thickness easy to understand, some suppliers use another system where the thickness is measured in 'ply', so 4 ply is the standard (1.5mm?) and 8 ply is double thick (3mm?).
I use a range of museum mountboards which have a solid colour throughout, they come in about 50 colours at 1.5mm, with about 6 colours at 3mm thick. Because the core is a solid colour you can easily laminate two 1.5mm boards together to give a good range of colours at 3mm thick. In the photos above I am laminating two 3mm thick boards together to give a monster 6mm thick piece of mountboard.
I mixed up some wheat starch paste and used a roller to spread over the board, put the boards together (cut at 24" x 32" which was slightly oversize so they could be cut to size after gluing) and weighted down with sheets of glass.
After a day the board was cut to size and then the bevelled aperture was cut on the mount cutter, I guess if you have a CMC (computerised mount cutter) then this thickness of board would be a doddle to cut, but with a manual cutter it takes a little bit of calibrating and fiddling about. You can see the mount cutter blade has had a small section removed to allow it to cut through fully, in this photo you can also see a test mount which was made from two different colours of board. Cutting was done at two depth increments as the blade was flexing too much in one cut. In the last photo you can see the finished result - a double double thick mount with a very big bevel.
