Chart Paper, 130 gsm

Details

Chart sheets, 55 cm by 70 cm, in packs of ten, twenty-five or fifty. Two numbers on a chart sheet are cut and both are measurable with a kitchen scale and a set square. Grammage first: a sheet printed 130 GSM that measures 105 to 110 is ordinary, and you find out when a marker strikes through onto the wall or the sheet under it. A 55 by 70 sheet at a true 130 GSM weighs 50 g, and at 110 GSM it weighs 42 g, which a school scale can tell apart in one weighing of ten sheets. The second is squareness. Chart sheets are cut in bulk on a guillotine that drifts, and a sheet that is out of square by 3 mm across the diagonal hangs visibly crooked on a wall no matter how carefully it is stuck.

• Measures 130 GSM to ISO 536, tolerance plus or minus 3 percent, so 126 to 134. A 55 by 70 cm sheet at 130 GSM weighs 50 g, and ten sheets weigh 500 g. Weigh the pack
• Opacity 95 percent, ISO 2471, so a water-based poster marker does not ghost through onto the sheet below or the wall behind
• Marker behaviour, stated honestly by marker type. A water-based poster or whiteboard marker will not strike through. A solvent-based permanent marker will strike through at 130 GSM, and no chart paper at this weight stops it. If you are using a permanent marker, put a sheet of newspaper under it
• Cut to 550 mm by 700 mm within plus or minus 1 mm, and square within 0.5 mm across the diagonal, checked on a sample from every pack
• Uncoated matt surface, so it takes a glue stick, a paper tape and a drawing pin without cockling, and it takes a pencil rule that can be erased
• ISO brightness 92 percent, ISO 2470-1. Bright rather than blue-white, and no optical brightener beyond the mill's standard furnish
• Virgin fibre and no recycled content, because a recycled 130 GSM sheet at this size loses the tear strength that keeps a chart from splitting off a drawing pin, and the board items in this range are where the recycled fibre sits
• Elemental chlorine free, AOX under 0.2 kg per tonne of pulp. ECF is not chlorine free and we will not round it up
• Packed flat in a paper band, not rolled. A rolled chart sheet keeps its curl for weeks and will not lie under a ruler
• Rs 24 a sheet at ten, Rs 21.60 at twenty-five, Rs 19.80 at fifty