Ok, I’m seeking 60 lb index paper.
Before you chime in, I know about those charts that purport to show paper equivalency. Supposedly what I want is equal to 40 lb cover, or 73 lb offset text or 29 bond ledger or 109.11 gsm. I can read the charts.
What is not made clear anywhere is what exactly is equivalent. Thickness? Feel? Are they in fact absolutely identical papers? I want index for a reason, and giving me a different paper that is physically as thick is not sufficient. If one had a piece of each of those papers and shuffled them, would a paper industry person be able to discern which is which? If they could, then equivalency means nothing to me. If they couldn’t, then my mystery is solved
Anyone out there actually know more about this? Google has failed me because no one seems to have asked this exact question.
The basis weight refers to how many pounds 500 sheets of a certain size weighs, but it’s a different size for each basis grade. Index paper basis size is 25.5"X30.5" while offset is 25"X30", so 60 lb index is equivalent in weight per square foot to the 73 lb offset as is the 40 lib cover which is a 20"X26" sheet.
They wouldn’t necessarily feel or look identical. Paper has different properties not accounted for by weight. Tear, tensile, stiffness, smoothness and brightness can all be different even with identical basis weights. While I spent most of my working life in the paper industry, I only made and bleached the pulp and am not an expert on these properties. Papermaking is one of those things that is as much art as science.
If I understand you correctly then the only real equivalence is weight and not thickness/texture. Then I’m screwed since it appears that no one online sells 60 lb index, and any of the so-called equivalents are not going to be what I want.
The thickness, or caliper, of all of those grades should be the same, with the proviso that there’s some hefty tolerance built into the measurements, plus or minus 5% is pretty common. The paper itself will have differing physical properties. A lot of paper is blended furnish, with both hardwood and softwood in the recipe. Softwood adds strength but hardwood has short fibers that can improve smoothness. Then there’s refining, which mechanically stresses the fibers to produce better fiber bonding. None of this show up on the label, so you’ve just got to try it out and see if it works.
If it were me, I’d just buy some ledger or offset and give it a try. 60 pound is pretty light for index, and I’m not surprised you can’t find a source for it.
Yeah I had a feeling things were going to go that way, Thanks for your info.
One thing you might find useful is comparing the gsm (grams per square meter) of the different papers, which avoids the minefield of figuring out the basis weights we use in our bizarre American system. You should find that in parentheses somewhere.
However, as Bill_Door has noted, caliper is not the whole story (and strictly speaking, gsm is not caliper) when comparing the “feel” of various paper stocks.