>If a paper is 250 grams os that 90lb or 120lb???? Please answer.
>Marilynn
Weight specified in pounds (lbs) is rather ambiguous. The weight in pounds
may mean "pounds per 1000 sq. ft." or it may be "pounds per ream of 500
sheets". Obviously, "pounds per ream" will depend on the size of each
sheet. And that is where the problem comes in. Paper can be sold as letter
size, cover size, text size, etc. In each case, a measurement given as
"lbs" may mean something very different because the base size of the paper
is different. I have reproduced a table below.
Weight given in "grams" generally means "grams per square meter" or "gsm"
and is a constant measurement which does not vary with the size of the sheets.
Cheers ...... Charles
From:
http://painting.about.com/od/artglossaryw/g/defweightpaper.htm
The thickness of a sheet of paper is indicated by its weight, measured
either in grams per square meter (gsm) or pounds per ream (lb). The
standard weights of machine-made paper are 190 gsm (90 lb), 300 gsm (140
lb), 356 gsm (260 lb), and 638 gsm (300 lb). It's generally recommended
that paper less than 356 gsm is
stretched
before use to prevent it buckling or warping.
This
from:
http://www.designtalkboard.com/designtalk/index.php/topic,1147.0.html
In a nutshell, the U.S. system is more difficult to understand because the
same number in #'s (pounds, or lbs) can be used for thicker card stock or
thinner text papers. Whereas the metric system is standard across all
weights of papers. For example, a card stock may be a 80# Cover or 80#
Text. But in the Metric system, the same papers would simply be 216 g/m²
and 104 g/m², respectively (the first being twice as thick as the second).
So when paper weight is specified in the US. you also have to specify its
dimensions/set size (as the same 'weight' can be applied to different size
paper). In places using the metric system, a paper weight is specified only
by its 'gsm', regardless of size. The difference arises because the metric
system also specify the AREA of paper the weight refers to i.e. grams per
square metre, whereas the US system refers to just the weight (in pounds)
so you also have to add the size. Trouble is, the US system makes it
difficult to compare papers directly, and you also have to know the paper
size that each term refers to (e.g. bond, offset, cover, tag, index).
This table from:
http://www.qslfactory.com/mix_n_match/inkjetqsls.html
BOND TEXT GSM
(lbs) (lbs)
size 17x22 in 25x38 in
20 50 75
24 60 90
28 70 105
32 80 120
35 90 131
43 110 160
50 130 210
[]