Looks like it's not as straightforward as I was hoping to find. Then, combine things like hot press vs. cold press and the mils can change even if the density or weight doesn't.
p.1 #3 · Paper Weights Conversion / Equivalence ...
It is a bigger nightmare than you can imagine. When it comes to "pound" weight there are all sorts of different measure systems, including basis weight, cover weight, tag weight, and bond weight. Here is a brief description with conversions:
Bond weight is the measure we think of most commonly but confusion can arise when the measure is not clear. Metric gram per square meter is unambiguous.
Note that RR also provides a few thickness examples. Due to large variations in density, there is never going to be a simple relationship between paper weight and thickness. The Palo Duro etching is a good example of the variation. Note that it is not that much heavier than ultra pro satin but is more than twice as thick.
I am probably providing more information than you want but there are some simple practical considerations. A light weight paper especially in larger sizes is difficult to handle without damaging it with slight creasing. I don't like to use anything lighter than about 250-270 gsm and 300 or so is even better. Next do not ignore paper thickness. When setting up a new paper profile knowing the thickness will help you set the proper head and platen gaps. (Epson did not provide any information about making these adjustments.) Of course the other consideration is paper feeding. My 3880 has 3 feed mechanisms depending on the thickness of the paper. Fortunately most papers will feed from the basic tray.
p.1 #5 · Paper Weights Conversion / Equivalence ...
Camperjim wrote:
It is a bigger nightmare than you can imagine. When it comes to "pound" weight there are all sorts of different measure systems, including basis weight, cover weight, tag weight, and bond weight. Here is a brief description with conversions:
Bond weight is the measure we think of most commonly but confusion can arise when the measure is not clear. Metric gram per square meter is unambiguous.
Note that RR also provides a few thickness examples. Due to large variations in density, there is never going to be a simple relationship between paper weight and thickness. The Palo Duro etching is a good example of the variation. Note that it is not that much heavier than ultra pro satin but is more than twice as thick.
I am probably providing more information than you want but there are some simple practical considerations. A light weight paper especially in larger sizes is difficult to handle without damaging it with slight creasing. I don't like to use anything lighter than about 250-270 gsm and 300 or so is even better. Next do not ignore paper thickness. When setting up a new paper profile knowing the thickness will help you set the proper head and platen gaps. (Epson did not provide any information about making these adjustments.) Of course the other consideration is paper feeding. My 3880 has 3 feed mechanisms depending on the thickness of the paper. Fortunately most papers will feed from the basic tray....Show more →
Thanks Jim. I guess I just have to understand that the numbers are not supposed to correlate ... i.e. treat them as different parameters. Since gsm is only area (two dimensions), the thickness would then be the 3rd dimension for volume ... weight then being the composite of all for a given size, etc.
I think I've got it now. For a given size (apples to apples) weight could correlate to GSM, but it would not give any indication of thickness (say hot press vs. cold press). So, GSM isn't a true density, just a mass per area. Thinner of same mass = more dense. Thicker of same mass = less dense.
