OK I'm trying to build some ISS parts and I notice I'm suppose to build in 110lb and 90lb paper. Is there a huge difference in how it will go together if I just use 110lb for all of it? What if I can only find 80lb instead?
Paper weights can be misleading, unless you understand how they are weighed.
"Cover" 65lb is Different than "Bristol Velum" 65lb. The difference is the sheet size used when it is weighed. Cover 65lb is almost the equivelant of Index 110lb, while the Bristol Velum is a light wieght compared to Index.
"Basis Weight Sheet Size" is the sheet size that a manufacturer will weigh (500-sheets). 500 sheets of 125lb Tag will be 24" x36" (size of basis sheet size) = 125lbs, while Index 110lb at 22.5" x 35" will weigh 110lbs.
The only measurement that works for all paper is the GSM (grams per square meter).
When building models, I like to stick to one Brand/weight of paper for each model. (Brand = Wasau, International Paper, Georgia Pacfic, etc..)
"Brightness" is a term used by the manufacturers to describe how their product looks undeneath a special blue light. Different types of cardstock have different "Brightness" numbers. This affects how the ink looks on the paer. Index is usually a brighter looking paper, while Tag has a yellow sheen if placed next to Index. (92-96 brightness Index vs., 84 Brightness for Tag).
Lots to learn when it comes to paper. The best answer for your question, " What difference is there in paper lb wise?" is to determine what type of paper you have, Bond, Tag, Cover, Index, Text, Vellum Bristol, etc and then compare the GSM to each other to find the ideal workablity, plus strength needed for your project.
67lb Vellum Bristol is easier to work with (form parts), while 110lb Index is great for strength.
After awhile you'll find a brand/weight that you like to use. A big factor is how easy your preferred brand is to get!
I created a chart from different paper info sites. It is old and doesn't show certain weights. Notice that GSM is shown as g/m2 in the right hand column.
Mike