Pick Glass is used to determine the reed and pick in woven fabric. Reed is actually number of ends or number of warp threads per inch and by picks we mean the number of picks or number of weft threads per inch. The following procedure is based on IS 1963: 1981 method:
Sampling
1. Avoid sampling within 50 mm from the selvedge.
2. Within two metres from either end of a piece or roll.
3. While sampling from design fabrics it is convenient to:
a) Determine the number of units in a weave repeat from a point paper diagram.
b) Count
i) The number of whole repeats
ii) The remaining units, in the distance across which the threads are to be counted.
iii) From the above data so obtained, the number of threads per centimetre or inch
both in warp way or weft way as required can be calculated.
Procedure
1. Keep the test sample on a flat table and smoothen it out.
2. Set the pointer of the counting glass at zero.
3. Place the counting glass on the fabrics in a direction parallel to warp if weft density is to
be determined and parallel to weft if warp density is to be determined.
4. Find the number of warp or weft threads in a specified length as required.
5. Following the procedure prescribed in steps 1 to 4, determine the number of warp and
weft threads per centimetre or inch in at least four more places.
6. Calculate the number of warp or weft threads per centimetre or inch by the following
formula: n = N ÷ L
Where
n = number of warp or weft threads per centimetre (or inch),
N = observed number of threads in the distance L, and
L = distance in centimetre (or inch) across which the threads are counted.
7. Calculate the mean of all the values and report it as the number of warp or weft threads
per centimetre or inch of the fabric.
Note: Avoid counting same set of warp or weft threads more than once. The value should be
rounded off to first decimal place in case when the results are reported for threads per cm.
An excellent tutorial on how to analyse a fabric using pick glass is found here.
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