Essentials matboard is buffered to be pH neutral (acid-free) and will provide 10-15 years of protection for your artwork. Matboard core is off-white in color. This mat is not of conservation quality.
Choosing an Opening Size Openings are cut to the size you specify; normally you will want an opening 1/2" smaller per dimension than your artwork. This gives space to hinge and prevents it falling through the mat opening. So, for example, an 8x10 photo would use a 7 1/2 x 9 1/2 opening.
Reveal A reveal is how much the bottom (or inner) mat shows in the opening. Common reveals are 3/16" or 1/4".
Please check that your chosen reveal and opening size still leaves at least a 1" border on all sides of the mat. For example, for a 10"x13" mat with a 3/16" reveal, the opening can be no larger than 7 5/8" x 10 5/8".