🧵 Mass per unit length (g/m) and mass per unit area (g/m²) of woven fabrics — methods 1–4 for whole pieces and sample lengths, method 5 on small specimens 10 cm × 10 cm; PN-ISO 3801

Materials and NDT PN-ISO 3801

Overview

WHAT THE STANDARD COVERS. ISO 3801:1977 (clause 1) specifies methods for the determination of the mass per unit length and the mass per unit area of woven fabrics conditioned in the standard atmosphere for testing. The methods apply to woven fabrics (including those of the “stretch” type) made up full width or folded down the middle, and to whole pieces as well as sample lengths. Introduction of the standard: the mass per unit length and per unit area may be determined in more than one way; for some fabrics the two are related simply by the width, but for others variations in structure (in the selvedges or in the body of the fabric) make an important distinction between them — so all possible methods must be considered and the one appropriate to the fabric chosen. None of the methods is so much more accurate than the others as to justify its being set up as the sole standard method; the choice (mass per unit length or area, a method for samples or for pieces) depends on circumstances. Where a cutting has been taken as a representative sample of a batch of pieces, the results on the sample may be used to correct measurements and masses of unconditioned pieces. References (clause 2): ISO 139 (standard atmospheres), ISO 3932 (determination of length of woven fabrics) and ISO 3933 (determination of width). The standard was prepared by ISO/TC 38 Textiles; first edition 1977-09-01, corrected and reprinted 1983-12-15.

PRINCIPLE OF THE METHODS (clause 3). Methods 1 and 3: when the piece or sample length can be conditioned in the standard atmosphere, the length and mass (method 1 — mass per unit length) or the length, width and mass (method 3 — mass per unit area) are determined. Methods 2 and 4: when conditioning the whole piece is impracticable, the length (and width) and mass of the piece are determined after relaxation in the prevailing atmosphere, and the result is corrected by a factor obtained by comparing a portion cut from that piece — measured first in the ambient atmosphere and then in the standard atmosphere. Method 5: when a small sample is tested, small samples are brought into equilibrium with the standard atmosphere, specimens of known dimensions are cut and weighed and the mass per unit area is calculated.

APPARATUS AND ATMOSPHERE (clauses 4–5). Calibrated steel rule 3 m long (failing this at least 2 m) graduated in centimetres and millimetres (methods 1–4); device for cutting a full-width specimen at right angles to the selvedge (methods 1–4); balance weighing pieces or sample lengths to ±0,2 % of the determined mass, and for method 5 — to 0,001 g; table with a smooth flat surface, wider than the fabric and at least 4 m long; device accurate to 1 % for cutting 10 cm × 10 cm specimens or a circular cutter of area 100 cm² and a metal plate about 9 cm × 9 cm (or 80 cm² with a circular plate) and 1 cm thick (method 5). Atmosphere for conditioning and testing — according to ISO 139; as worded in the 1977 standard: relative humidity 65 ± 2 % and temperature 20 ± 2 °C, and in tropical regions, subject to agreement of the parties, 27 ± 2 °C.

PROCEDURE (clause 6). Pre-conditioning (6.1): equilibrium is approached from the dry side; if the fabric does not permit this, it is pre-conditioned in an atmosphere with a relative humidity not exceeding 10 % and a temperature not higher than 50 °C, until the difference between successive weighings at intervals of at least 2 h does not exceed 0,5 % of the final mass. Selvedges (6.2): if the mass per unit length (or area) of the selvedge differs appreciably from that of the fabric, the mass per unit area is determined on a sample with the selvedges removed (along the outermost warp threads of the body), and the calculation is based on the mass, length and width of the trimmed sample. Method 1 (6.3): pieces — conditioned length of the piece according to ISO 3932, then weighing without removing it from the standard atmosphere; where the full length cannot or need not be determined — the procedure for sample lengths on a sample at least 0,5 m long, preferably 3–4 m, taken preferably from the middle of the piece; sample lengths — cut across the full width along parallel lines at right angles to the selvedge. Method 2 (6.4): length of the piece after relaxation in the ambient atmosphere (ISO 3932) and its mass in this atmosphere; from the middle of the piece a full-width sample at least 1 m long, preferably 3–4 m; the masses of the piece and of the sample are determined at the same time to minimize the effect of sudden changes of temperature and humidity, and the sample is then treated as in 6.3.2.2. Method 3 (6.5): as method 1 plus the conditioned width according to ISO 3933. Method 4 (6.6): as method 2 plus the width of the piece after relaxation and the width of the sample after relaxation and after conditioning (ISO 3933). Method 5 (6.7): five samples (unless otherwise specified) about 15 cm × 15 cm, free of selvedges and creases, as representative as possible; with a large pattern, where different areas have appreciably different mass per unit area — samples containing an integral number of complete pattern repeats; pre-conditioning according to 6.1, then at least 24 h tension-free in the standard atmosphere; from each sample, under the metal plate, a 10 cm × 10 cm square (or a 100 cm² circle) is cut and weighed to ±0,001 g, without loss of threads.

CALCULATION AND TEST REPORT (clauses 7–8). Methods 1 and 3: mass per unit length = mc / lc (g/m), mass per unit area = mc / (lc × wc) (g/m²), where mc — mass after conditioning (with or without selvedges, as relevant), lc and wc — length and width after conditioning in metres; the result is rounded to the nearest gram. Methods 2 and 4: the conditioned length (and width) of the piece is calculated according to ISO 3932 (ISO 3933), and the conditioned mass of the piece from mc = mr × msc / msr (mass of the piece after relaxation times the ratio of the masses of the sample after conditioning and after relaxation); then as in 7.1, rounded to the nearest gram. Method 5: mass per unit area = m × 100 (g/m²), where m — mass of the 100 cm² specimen in grams; mean of the five values, rounded to the nearest gram. Test report: reference to the standard, the result for each specimen (when more than one is tested), date, mean mass per unit length and/or area, the method (1, 2, 3, 4 or 5) by which each result was obtained, whether the result includes the selvedges, deviations from the procedure.

STATUS (PKN card as of 06.11.2026). The card of PN-ISO 3801:1993 (Polish version) bears the label “Withdrawn”: publication date 17-08-1993, withdrawal date 18-09-2014, 6 pages, Consumer Products Sector, KT 26 Textile Products, “Adopts: ISO 3801:1977 [IDT]”, “Replaces: PN-P-04613:1985 - Polish version”, ICS 59.080.30. The card has no “Replaced by” line — PKN does not indicate a standard that replaced PN-ISO 3801:1993. The “Scope” field (in Polish): “This International Standard gives methods for the determination of: a) mass per unit length, b) mass per unit area of woven fabrics conditioned in the standard atmosphere.” What this means for the result: the withdrawal does not change the content of the method — the Polish standard adopted ISO 3801:1977 unchanged [IDT], and the ISO text we read is the text of this method — but the laboratory works according to a withdrawn standard with no successor indicated by PKN, and the report should cite it with its year of publication. The same item of AB 154 contains PN-P-04613:1997 — the number of the standard that PN-ISO 3801 replaced in its 1985 edition; we did not check the status of the 1997 edition.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database of 02.11.2026; “Laboratories” tab on labcoda.pl, 06.11.2026). The number 3801 appears in 7 records at 6 Polish laboratories: AB 154, AB 164 (two records — the same content, different notation of points), AB 198, AB 225, AB 403, AB 1417. The form is always “PN-ISO 3801:1993” — without points (AB 154, AB 198, AB 1417), with points 6.3, 6.5, 6.7 (AB 164, AB 403) or with point 6.7 only (AB 225). At AB 154 the standard is in one item with PN-EN 12127:2000, PN-EN ISO 9073-1:2023-11 and PN-P-04613:1997. We count the form “3801” not followed by a digit; outside Poland there is 1 Czech record (1001 — “ISO 3801” in one item with ČSN 80 0845, ČSN EN ISO 9073-1, ČSN 80 0863, ČSN EN ISO 9864, ČSN EN 984, ČSN EN 12127 and ČSN EN ISO 23997). The “Laboratories” tab (“PN-ISO 3801”) shows 7 laboratories: these 6 Polish and 1 Czech, with the same number of items as the copy (query of the tab on labcoda.pl, 06.11.2026). We did not compare the current PCA scope documents of these laboratories with the copy.

WHAT THE LABORATORIES TEST (database copy, complete items). Woven fabrics — mass per unit length with the parameter “mass per unit area”, technique “Method 1; Method 3; Method 5”, points 6.3, 6.5 and 6.7 (AB 164, two records); textile fabrics, knitted fabrics, woven fabrics and textile products — mass per unit length and per unit area, technique “indirect method”, points 6.3, 6.5 and 6.7 (AB 403); woven fabrics — mass per unit area, “Method 5 – small sample”, point 6.7 (AB 225); woven fabrics — mass per unit area (AB 1417); woven fabrics — mass per unit length and per unit area (AB 198); textile fabrics — mass per unit length and per unit area, together with PN-EN 12127:2000, PN-EN ISO 9073-1:2023-11 and PN-P-04613:1997 (AB 154). No item gives a measuring range.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Sampling: in method 5 the 15 cm × 15 cm samples must avoid selvedges and creases and, with a large pattern, contain an integral number of pattern repeats — otherwise the mean of five squares does not represent the fabric; the standard itself warns that method 5 may then be unsuitable, especially in a dispute. Measurement: equilibrium with the standard atmosphere is approached from the dry side (pre-conditioning at humidity up to 10 % and temperature up to 50 °C); a moist sample conditioned “from the wet side” gives a different mass in the same atmosphere. The conditioned mass is weighed without removing the piece or sample length from the standard atmosphere (points 6.3.1, 6.3.2.2), and in methods 2 and 4 the masses of the piece and of the sample length in the ambient atmosphere — at the same time (point 6.4). Calculation: mass per unit length and mass per unit area are not always related by the width (introduction of the standard) — converting one into the other instead of measuring gives a seemingly consistent result; in methods 2 and 4 the conditioned mass of the piece is a calculated quantity: the mass of the piece after relaxation and the mass of the sample length after relaxation are measurements in the ambient atmosphere, the mass of the sample length after conditioning — a measurement in the standard atmosphere, and the conditioned length and width are calculated according to other standards (ISO 3932, ISO 3933). A result with and without selvedges are two different numbers — the report must say which. The scopes combine the standard with PN-EN 12127 (mass per unit area on small samples — a separate entry of this database) and with nonwoven standards; the result must state according to which standard and which method it was obtained.

WHAT WE DO NOT GIVE. The text of ISO 3801:1977 we read (iTeh sample, corrected and reprinted 1983-12-15) covers the whole standard — introduction, clauses 1–8; it does not contain the text of the Polish standard PN-ISO 3801:1993, so we do not quote the Polish wording. We do not give the current wording of ISO 139 (the standard atmosphere is given here as quoted by the 1977 standard) or the content of ISO 3932 and ISO 3933. The status of ISO 3801 at the publisher (ISO) could not be read — the ISO page was not accessible from our machine. We did not check references to the standard in legislation.

Method principle

The mass of a fabric conditioned in the standard atmosphere is divided by its length (mass per unit length, g/m) or by its length and width (mass per unit area, g/m²): in methods 1 and 3 on the whole piece or sample length, in methods 2 and 4 on a piece measured in the ambient atmosphere with a correction from a sample length measured in both atmospheres (mc = mr × msc / msr), in method 5 — from the mass of five small specimens of 100 cm² (mass per unit area = m × 100); the result is rounded to the nearest gram (ISO 3801:1977, clauses 3, 6, 7).

Applications

• Woven fabrics, including the “stretch” type, full width or folded down the middle — whole pieces and sample lengths (ISO 3801:1977, clause 1)
• Mass per unit length (g/m) — methods 1 and 2; mass per unit area (g/m²) — methods 3, 4 and 5
• Pieces that cannot be conditioned in the standard atmosphere — methods 2 and 4 with a correction from a sample length
• In accreditation scopes: 6 Polish laboratories — woven fabrics, textile fabrics, knitted fabrics; methods 1, 3 and 5 (points 6.3, 6.5, 6.7)

Key parameters

Standard

Standard number

PN-ISO 3801:1993 (Polish version; adopts ISO 3801:1977 [IDT]; withdrawn on 18-09-2014)

Title (PL)

Tekstylia — Tkaniny — Wyznaczanie masy liniowej i powierzchniowej

Title (EN)

Textiles — Woven fabrics — Determination of mass per unit length and mass per unit area

Step-by-step procedure

1. Choice of method

   Mass per unit length or area; whole piece, sample length or small sample; whether the piece can be conditioned in the standard atmosphere (methods 1/3) or not (methods 2/4); with a large pattern — caution with method 5 (introduction, clause 3).

2. Conditioning

   Equilibrium from the dry side — if necessary pre-conditioning at humidity ≤ 10 % and temperature ≤ 50 °C; then the standard atmosphere (method 5: at least 24 h tension-free) (points 6.1, 6.7.2).

3. Selvedges

   Where the mass of the selvedge differs appreciably from that of the fabric — mass per unit area on a sample with the selvedges removed (point 6.2).

4. Measurement

   Methods 1 and 3: length (ISO 3932), width (ISO 3933) and mass without removal from the standard atmosphere; methods 2 and 4: piece and sample length after relaxation in the ambient atmosphere, weighed at the same time, then the sample length conditioned; method 5: five 10 × 10 cm squares (or 100 cm² circles) weighed to ±0,001 g (points 6.3–6.7).

5. Calculation and result

   mc/lc (g/m), mc/(lc × wc) (g/m²); methods 2 and 4: mc = mr × msc/msr; method 5: m × 100, mean of five; rounding to the nearest gram; the report states the method and whether the result includes the selvedges (clauses 7–8). PN-ISO 3801:1993 — withdrawn on 18-09-2014 with no successor indicated (PKN card as of 06.11.2026).

Required equipment and apparatus

Health and safety (OHS)

• TECHNICAL NOTE: method 5 may be unsuitable for fabrics with a large pattern and in disputes (introduction of the standard)
• TECHNICAL NOTE: a result with and without selvedges are two different quantities — the report must state which is given
• Work with sharp cutters — the metal plate holds the specimen during cutting (points 4.6, 6.7.2)

Frequently asked questions