ASTM C474-15(2020)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C474 − 15 (Reapproved 2020)
Standard Test Methods for
Joint Treatment Materials for Gypsum Board Construction
This standard is issued under the fixed designation C474; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods cover the physical testing of joint
ization established in the Decision on Principles for the
compound, paper joint tape, glass-mesh joint tape, and an
Development of International Standards, Guides and Recom-
assembly of joint compound and paper joint tape.
mendations issued by the World Trade Organization Technical
1.1.1 Joint treatment materials are specified in Specification
Barriers to Trade (TBT) Committee.
C475/C475M.
1.1.2 The joint treatment material described in this standard
2. Referenced Documents
are for use with gypsum board installed in accordance with
Specification C840.
2.1 ASTM Standards:
1.2 The test methods appear in the following order: C11Terminology Relating to Gypsum and Related Building
Materials and Systems
Joint Compound Tests:
Viscosity 5
C472Test Methods for Physical Testing of Gypsum, Gyp-
Shrinkage 6
sum Plasters, and Gypsum Concrete
Check Cracking 7
C475/C475MSpecification for Joint Compound and Joint
Putrefaction 8
Joint Tape Tests:
Tape for Finishing Gypsum Board
Tensile Strength 9
C840SpecificationforApplicationandFinishingofGypsum
Width 10
Board
Thickness 11
Paper Joint Tape Tests:
C1396/C1396MSpecification for Gypsum Board
Dimensional Stability 12
D685Practice for Conditioning Paper and Paper Products
Assemblages of Paper Joint Tape and Joint Compound:
for Testing
Bond of Paper Joint Tape to Joint Compound 15
Cracking of Joint Compound at Tape Edges 14
D828Test Method for Tensile Properties of Paper and
Glass-Mesh Joint Tape Test:
PaperboardUsingConstant-Rate-of-ElongationApparatus
Skewness 13
D1000 Test Methods for Pressure-Sensitive Adhesive-
1.3 The values stated in inch-pound units are to be regarded
Coated Tapes Used for Electrical and ElectronicApplica-
as standard. The values given in brackets are mathematical
tions
conversions to SI units that are provided for information only
D3699Specification for Kerosine
and are not considered standard.
D3882Test Method for Bow and Skew in Woven and
1.4 The text of this standard references notes and footnotes
Knitted Fabrics
that provide explanatory material. These notes and footnotes
E100Specification for ASTM Hydrometers
(excluding those in tables and figures) shall not be considered
E177Practice for Use of the Terms Precision and Bias in
as requirements of the standard.
ASTM Test Methods
E691Practice for Conducting an Interlaboratory Study to
1.5 This standard does not purport to address all of the
Determine the Precision of a Test Method
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
2.2 TAPPI Standard:
priate safety, health, and environmental practices and deter-
T411 Thickness (Caliper) of Paper, Paperboard, and Com-
mine the applicability of regulatory limitations prior to use.
bined Board
These test methods are under the jurisdiction of ASTM Committee C11 on
Gypsum and Related Building Materials and Systems and are the direct responsi- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
bility of Subcommittee C11.02 on Specifications and Test Methods forAccessories contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and Related Products. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2020. Published June 2020. Originally the ASTM website.
approved in 1961. Last previous edition approved in 2015 as C474–15. DOI: Available from TechnicalAssociation of the Pulp and Paper Industry, Technol-
10.1520/C0474-15R20. ogy Park, P.O. Box 105113, Atlanta, GA 30348.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C474 − 15 (2020)
3. Terminology 5.2.1 Sampling shall be in accordance with Specification
C475/C475M.
3.1 Definitions—For definitions of terms relating to
gypsum, see Terminology C11. 5.3 Specimen Preparation:
3.2 Definitions of Terms Specific to This Standard: 5.3.1 Prepare specimens in accordance with Section 4.
3.2.1 bond, n—in joint systems, the quality of adhesion
5.4 Apparatus:
between the paper joint tape and joint compound.
5.4.1 Viscosity Specimen Container,metalorplasticwithan
3.2.1.1 Discussion—A0% bond means that no paper fiber
open top having an inside diameter of 2 ⁄2to 3 in. [65 to
is adhering to the joint compound. 100% bond means that
75mm] and a height of 2 ⁄2to 3 in. [65 to 75 mm].
there is cohesive failure of the paper joint tape. 4
5.4.2 Viscometer , adjusted to operate at 78 6 1 r/min.
3.2.2 check cracking, n—in joint systems, short, narrow
5.4.3 Viscometer Pin (Spindle), having dimensions as fol-
cracks randomly oriented in the surface of the dried joint
lows:
compound.
in. [mm]
Shaft diameter 0.187 ± 0.015 [4.75 ± 0.38]
3.2.3 joint compound, powder, n—a drying-type or setting-
Pin diameter 0.094 ± 0.015 [2.39 ± 0.38]
type cementitious material to be mixed with water.
Immersion depth (from bottom of spindle) 1.625 ± 0.015 [41.3 ± 0.38]
Length of pin projecting from shaft 0.750 ± 0.015 [19.1 ± 0.38]
3.2.4 joint compound, ready-mix, n—a drying-type cemen-
Upper pin from bottom of shaft 0.313 ± 0.015 [7.95 ± 0.38]
titious material that is factory mixed in ready-to-use form.
Lower pin from bottom of shaft 0.125 ± 0.015 [3.28 ± 0.38]
5.5 Procedure:
4. Specimen Preparation
5.5.1 Fill the viscosity container with the mixed specimen
until level with the top of the container.
4.1 Joint Compound, Powder:
5.5.1.1 Remove all air bubbles by puddling the sample
4.1.1 Mix 300 g of joint compound, powder, with approxi-
container with a spatula and sharply rapping the bottom of the
mately 150 to 160 mL of water.
container on a hard flat surface.
4.1.2 Allow the specimen to stand for 30 min (Note 1),
5.5.2 Securethefilledcontainerinthecenteroftheviscom-
remix and adjust the temperature to 77 62°F[25 6 1 °C] by
eter spindle platform. Position the spindle so that the sample
placing the container holding the specimen in warm or cool
comes up to the immersion mark on the pin (spindle).
water.
5.5.3 Start the viscometer and record the viscosity reading
NOTE 1—Allow setting type compounds to stand for one half of their
on the digital display after 30 s. If the viscometer readout goes
setting times, as determined by Test Methods C472 but not more than
to a strip chart recorder, read the viscosity after the pen starts
30min, prior to remixing.
to trace a straight line (usually within 1 min); if the tracing
4.1.3 Measure the viscosity in accordance with Section 5.
remains inconsistent, estimate the average viscosity reading.
4.1.4 If the measured viscosity is not between 480 and
5.6 Report:
520Brabender units, repeat 4.1.1 – 4.1.3 through with an
5.6.1 Report the viscosity of the joint compound specimen
increase or decrease in water as necessary.
in Brabender units.
4.1.5 Record the volume of water used to adjust the viscos-
ity to 500 6 20 Brabender units (see Note 2).
5.7 Precision and Bias:
5.7.1 The precision of this test method is based on an
NOTE 2—Making note of the volumes of water, in millilitres per 100 g
interlaboratory study conducted in 2011. Seven laboratories
of material, used to adjust the viscosity, will facilitate specimen prepara-
tion in other tests.
using Brookfield equipment and eight laboratories using Bra-
bender equipment tested two different materials, by alternative
4.2 Joint Compound, Ready-Mix:
methods. Every test result represents an individual
4.2.1 Remix joint compound, ready-mix, to reincorporate
determination, and each lab was asked to report five replicate
any separated ingredients.Adjust the temperature to 77 62°F
results for each material/instrument combination. Except for
[25 6 1 °C] by placing the container holding the specimen in
the limited amount of data reported for several of the material/
warm or cool water.
instrument combinations, Practice E691 was followed for the
4.2.2 Measure the viscosity in accordance with Section 5.
design and analysis of the data.
4.2.3 If the viscosity is more than 520 Brabender units, add
5.7.1.1 Repeatability Limit (r)—Two test results obtained
water to achieve a viscosity of 500 6 20 Brabender units (see
within one laboratory shall be judged not equivalent if they
Note 2).
differ by more than the “r” value for that material; “r” is the
4.2.3.1 If the original sample viscosity is less than 480Bra-
interval representing the critical difference between two test
bender units, test as received.
results for the same material, obtained by the same operator
JOINT COMPOUND
5. Joint Compound Viscosity The sources of supply of the apparatus known to the committee at this time are
the Brabender “Visco-Corder” Model VC-E, manufactured by C.W. Brabender
5.1 Significance and Use:
Instruments Inc., South Hackensack, NJ. and the Brookfield R/S-SST Rheometer,
5.1.1 This test method provides a procedure for measuring manufactured by Brookfield Engineering Laboraties Inc., Middleboro, MA. If you
are aware of alternative suppliers, please provide this information to ASTM
joint compound viscosity.
International Headquarters. Your comments will receive careful consideration at a
5.2 Sampling: meeting of the responsible technical committee, which you may attend.
C474 − 15 (2020)
TABLE 1 Brookfield R/S SST (Brabender Units) TABLE 2 Brabender VC-E (Brabender Units)
Repeat- Reproduc- Repeat- Reproduc-
Repeat- Reproduc- Repeat- Reproduc-
ability ibility ability ibility
A A
Material Average ability ibility Material Average ability ibility
Standard Standard Standard Standard
x x
ID Limit Limit ID Limit Limit
Deviation Deviation Deviation Deviation
r R r R
S S S S
r R r R
Sample A 660.0 7.6 23.6 21.2 66.0 Sample A 602.7 7.2 28.3 20.1 79.3
Sample B 133.6 1.8 5.7 5.2 15.9 Sample B 123.1 1.9 8.0 5.4 22.4
A A
The average of the laboratories’ calculated averages. The average of the laboratories’ calculated averages.
using the same equipment on the same day in the same
laboratory. Repeatability limits are listed in Tables 1 and 2
6.4.2 Balance,havingasensitivityof10mg(Figs.1and2).
below.
6.4.3 Beaker, Ring Stand, and Wire Cradle (see Fig. 1).
5.7.1.2 Reproducibility Limit (R)—Two test results shall be
6.4.4 ForcedAir Drying Oven, capable of being maintained
judgednotequivalentiftheydifferbymorethanthe“R”value
at 90 to 120 °F [32 to 49 °C].
for that material; “R” is the interval representing the critical
6.4.5 Spatula, having a blade approximately 4 in. by ⁄2in.
difference between two test results for the same material,
[100 by 13 mm].
obtained by different operators using different equipment in
6.4.6 Steel-reinforced Broad Knife, a 5 to 8 in. [130 by
different laboratories. Reproducibility limits are listed in
200mm] drywall broad knife reinforced by a steel bar, 1 in.
Tables 1 and 2 below.
[25mm] wide by ⁄8in. [3 mm] thick, by the knife width,
5.7.1.3 The above terms (repeatability limit and reproduc-
attached to the back of the knife blade ⁄4in. [6 mm] from the
ibility limit) are used as specified in Practice E177.
edge.
5.7.1.4 Any judgment in accordance with statements 9.1.1
6.4.7 Hydrometer, having a range of 0.7 to 0.8 sp gr, in
and 9.2 would have an approximate 95% probability of being
accordance with Specification E100.
correct.
6.4.8 Volumetric Container, a container which has a volume
5.7.2 Bias—At the time of the study, there was no accepted
between 25 and 300 cm .
referencematerialsuitablefordeterminingthebiasforthistest
method, therefore no statement on bias is being made.
6.5 Reagents and Materials:
5.7.3 The precision statement was determined through sta-
6.5.1 Displacement Fluids.
tistical examination of 296 results, by alternative methods, on
6.5.1.1 Mineral Spirits, odorless.
two materials (described below).
6.5.1.2 Kerosine (see Specification D3699).
5.7.3.1 Sample A—A representative conventional weight
6.6 Preparation of Apparatus:
ready-mixed all-purpose joint compound prepared specifically
6.6.1 Support Plates—Cover three plastic or glass plates
for the round-robin test and distributed to all testing laborato-
with plastic or rubber film.
ries.
6.6.2 Obtain and record the tare weight of each assembly.
5.7.3.2 Sample B—A representative low-viscosity wall tex-
6.7 Calibration:
ture compound prepared specifically for the round-robin test
6.7.1 Volumetric Container—Determine the container vol-
and distributed to all testing laboratories.
ume in cubic centimetres and its tare weight in grams.
6. Shrinkage
6.7.2 Mineral Spirits, Kerosine—Using the hydrometer, de-
termine the specific gravity and record the result as density M,
6.1 Significance and Use:
g/mL.
6.1.1 Thistestisusedtomeasuretheamountofshrinkagein
joint compound. The degree of correlation between this test
6.8 Determination of Density of Wet Compound:
and service performance has not been determined.
6.8.1 Prepare a specimen to determine the density of wet
compound by weighing the specimen in the volumetric con-
6.2 Sampling:
tainer.
6.2.1 Sampling shall be in accordance with Specification
6.8.1.1 Adjust the temperature to 70 62°F[21 6 1 °C] by
C475/C475M.
placing the container holding the specimen in warm or cool
6.3 Specimen Preparation:
water.
6.3.1 Specimen preparation shall be in accordance with
6.8.1.2 Puddle the specimen within the container with the
Section 4.
spatula to remove entrapped air bubbles.
6.4 Apparatus:
6.8.1.3 Finish filling the container and strike off the surface
6.4.1 Plastic or Rubber Film, approximately 5 by 5 in. [130
flush with the top using the steel-reinforced broad knife.
by 130 mm]. Any thin, flexible film that peels clean from a
6.8.1.4 Weigh the filled container to the nearest 0.01 g.
partially dried patty may be used.
Record the weight of the filled container.
6.8.1.5 Determine the net weight of the compound in the
5 volumetric container by subtracting the weight obtained in
Rubber dental dam dusted with talc, polyethylene, or PTFE films have been
found satisfactory for this use. 6.8.1.4 from the weight obtained in 6.7.1.
C474 − 15 (2020)
FIG. 1 Wire Cradle in Kerosine
FIG. 2 Patty Immersed in Kerosine
6.8.1.6 Divide the net weight obtained in 6.8.1.5 by the 6.9 Preparation of Specimen to Determine Wet and Dry
volume of the container obtained in 6.7.1. Record the result as Volume:
wet compound density G, g/mL.
6.9.1 Place approximately 30 g of specimen onto each
prepared support plate (see 6.6.1).
totalweight 2 containertareweight
G 5 (1)
volumeofcontainer
C474 − 15 (2020)
6.9.1.1 Spread the specimen into an elongated patty ⁄16 to 6.12 Report:
⁄4in. [5.0 to 6.5 mm] thick with a spatula. 6.12.1 Taketheaverageofthethreepattiestested.Ifthereis
6.9.1.2 Remove any specimen remaining on the spatula and
a difference between the percent shrinkage of the three patties
add to the patty. of more than 1.5%, completely retest an additional three
specimens and take the average of the six.
NOTE 3—The patty may be scored across its narrowest width to
facilitate breaking the patty after it is dry.
6.13 Precision and Bias:
6.13.1 Precision and bias of this test method have not been
6.9.1.3 Weighandrecordthetotalweightofeachpatty,film,
determined.
and plate.
6.9.1.4 Determine the net weight of each specimen by
7. Check Cracking of Joint Compound
subtracting the tare weight of its support plate weight and the
weight obtained in 6.9.1.3.
7.1 Significance and Use:
6.9.1.5 Divide the net weight obtained in 6.9.1.4 by G.
7.1.1 This test method is used to measure the degree and
Record as wet volume of patty V, mL.
type of field and edge cracking of joint compound.The degree
of correlation between this test and service performance has
wetpattyweight 2 supportplatetareweight
V 5 (2)
G not been determined.
6.10 Determination of Dry Volume:
7.2 Sampling:
6.10.1 Dry patties at a temperature between 100 and 120 °F 7.2.1 Sampling shall be in accordance with Specification
[32 to 49 °C] for 16 to 24 h.
C475/C475M.
6.10.1.1 When testing setting type joint compounds, place
7.3 Specimen Preparation:
thepattiesinthedryingoven1hafterthesettingtimehasbeen
7.3.1 Prepare specimens in accordance with Section 4,
reached as determined by Test Methods C472.
except use a quantity of 100 g.
6.10.1.2 When testing drying type joint compounds, place
7.4 Apparatus:
the patties in the drying oven immediately after weighing.
7.4.1 Rod, metal or glass, ⁄8in. [3.2 mm] in diameter by
6.10.2 Strip off the plastic or rubber film, and continue to
7in. [180 mm] in length.
dry under the conditions specified in 6.10.1 until constant
7.4.2 Steel-reinforced Broad Knife, as defined in 6.4.6.
weight is reached.
7.4.3 Gypsum Wallboard, Specification C1396/C1396M.
6.10.3 Immerse each patty in a beaker of the displacement
7.4.3.1 To determine compliance to Specification C475/
fluid, such that they do not touch the sides of the beaker, for a
C475M,SpecificationC1396/C1396Mgypsumwallboardshall
minimum of 4 h, until constant weight is reached.
be used.
NOTE4—Eachpattymaybebrokenintotwoorthreepiecestofitinthe
beaker without touching the sides.
NOTE 5—Other substrates may be used to evaluate the effect that they
have on the performance of the joint compound and assemblies of joint
6.10.4 Remove each patty from the displacement fluid.
compound and joint tape.
Using a cloth moistened in the same fluid, lightly blot off the
7.4.4 Electric Fan, capable of forcing a continuous current
excess fluid from the surface of the patty.
of air at a velocity of 350 to 450 ft/min [1.8 to 2.3 m/s] at a
6.10.5 With the wire cradle suspended in the beaker of
distance of approximately 3 ft [1 m].
displacement fluid, weigh each patty in air on the pan of the
balance (Fig. 1), and record as its air weight.
7.5 Procedure:
6.10.6 Next, weigh each patty in the wire cradle, ensuring
7.5.1 Place the rod on a piece of gypsum wallboard and
that the patty is completely immersed in the liquid and that it
place some of the specimen next to the rod.
does not touch the sides of the beaker (Fig. 2). Record these
7.5.2 Form a 3 ⁄2to 4 in. [90 to 100 mm] wide wedge of the
weights as the immersed weight.
specimenwiththesteel-reinforcedbroadknife,withtherodon
6.10.7 Subtract the immersed patty weight obtained in
onesideandthewallboardontheothersidetoguidetheknife.
6.10.6 from the air patty weight obtained in 6.10.5. Record as
7.5.2.1 Hold the broad knife at an angle less than 45° with
D,theweightdifference,whichistheweightoffluiddisplaced
respect to the plane of the wallboard. Draw the broad knife
by the dried and then saturated patty.
over the specimen two or more times to leave the surface
6.10.8 Divide D, the weight difference, by M, the density of
smooth.
the displacement fluid determined in 6.7.2, and record as dry
7.5.3 Remove the rod and adjust the wedge toa5in.
volume of patty, R, mL.
[130mm] length.
7.5.4 Immediately place the wedge-shaped specimen in
R 5 D/M (3)
front of the fan blowing over the surface of the wedge for 8 to
6.11 Calculation of Shrinkage:
16 h. The current of air shall be maintained at 70 to 85 °F [21
6.11.1 Calculate the percent shrinkage as follows:
to 29 °C] and 45 to 55% relative humidity.
% shrinkage 5 @1 2 ~R/V!# 3100 (4)
7.6 Report:
where:
7.6.1 Report the type and amount of cracking in both the
R = volume of the dry patty, and thick half and the thin half of the wedge.
V = volume of the wet patty.
7.7 Precision and Bias:
C474 − 15 (2020)
7.7.1 Precision and bias of this test method have not been 9.1.1 This test method is used to evaluate the cross-
determined. directional strength of joint tape used to reinforce the joints
created by gypsum wallboard construction. The degree of
8. Putrefaction
correlation between this test and service performance has not
been determined.
8.1 Significance and Use:
8.1.1 This test method is used to evaluate the tendency of
9.2 Sampling:
the joint compound to putrefy. The degree of correlation
9.2.1 Sampling shall be in accordance with Specification
between this test and service performance has not been
C475/C475M.
determined.
9.2.2 Asampleforthepurposeoftestingshallconsistofnot
8.2 Sampling:
less than 12 ft [3.6 m] of tape from each roll.
8.2.1 Sampling shall be in accordance with Specification
9.2.3 Take ten specimens in the cross direction at not less
C475/C475M.
than 1 ft [300 mm] intervals. Cut each specimen to 1 in.
[25mm] by roll width.
8.3 Apparatus:
8.3.1 Humidity Cabinet, a chamber capable of maintaining
9.3 Apparatus:
85 to 95 °F [29 to 35 °C] and 85 to 95% relative humidity.
9.3.1 The apparatus shall be in accordance with Test
8.3.2 Glass Container, capable of being sterilized in an
Method D828 except that the distance of the jaw spacing shall
autoclave, having a minimum volume of 250 mL.
1 1
be reduced to ⁄2 6 ⁄64in. [12.7 6 0.4 mm]; the rate of
8.3.3 Cover,madeofglassoraluminumfoillargeenoughto
elongation shall be 0.66 in./min 6 5 s [17 mm/min 6 5 s].
cover the glass container and capable of being sterilized in an
9.4 Procedure:
autoclave.
9.4.1 Condition the specimens for a minimum of 24 h at 72
8.3.4 Autoclave, capable of maintaining 260 °F [130 °C] at
64°F[22 6 2 °C] and 50 6 2% relative humidity.
21 psi [145 kPa] steam pressure for not less than 15 min.
9.4.2 Test in accordance with Test Method D828 with
8.4 Preparation of Apparatus:
equipment as set forth in 9.3.
8.4.1 Sterilize the glass container and cover in an autoclave
at 21 psi [145 kPa] and 260 °F [130 °C] for 15 min or more. 9.5 Interpretation of Results:
9.5.1 Accept or reject results of the individual test speci-
8.5 Procedure:
mens in accordance with Test Method D828.
8.5.1 Joint Compound, Powder—Mix 50 g of joint com-
9.5.2 Ifanyresultsarerejected,testadditionalspecimensso
pound with water, as determined in 4.1 in the glass container.
that there are at least ten test results for the evaluation of any
Allow it to soak 30 min and then remix. Place the cover over
unit of tape.
the glass container and place in the humidity cabinet.
8.5.2 Joint Compound, Ready-mix—Select an unopened
9.6 Report:
container that has not exceeded the producer’s specified shelf
9.6.1 Report test results as pounds-force per inch (Newtons
life.
per millimetre) of width of specimen.
8.5.2.1 Open the container. If the material in the container
9.7 Precision and Bias:
has separated, mix thoroughly.
9.7.1 Precision and bias statements as listed in Test Method
8.5.2.2 Remove 100 g of joint compound, ready-mix, from
D828 are suitable for use with this product.
the container.
8.5.2.3 Put the specimen in the glass container and cap with
10. Width
the cover.
8.5.2.4 Place in the humidity cabinet.
10.1 Significance and Use:
8.6 Interpretation of Results: 10.1.1 This test method is used to determine the average
8.6.1 Observe daily for putrefaction. variation in width of the joint tape. The degree of correlation
between this test and service performance has not been
8.7 Report:
determined.
8.7.1 Report the number of days required to produce putre-
faction.
10.2 Sampling:
10.2.1 Sampling shall be in accordance with Specification
8.8 Precision and Bias:
C475/C475M.
8.8.1 Precision and bias of this test method have not been
determined.
10.3 Specimen Preparation:
10.3.1 Cut a specimen of joint tape not less than 12 ft
JOINT TAPE
[3.5m] long from the roll to be tested.
9. Tensile Strength
10.4 Apparatus:
9.1 Significance and Use: 10.4.1 Steel Rule, Caliper Rule, or other measuring device
capableofresolving ⁄32in.Ametricdevicemustbecapableof
resolving 1.0 mm.
Deep Petri dishes and 250 mL beakers have been found suitable for this
purpose. 10.5 Procedure:
C474 − 15 (2020)
FIG. 3 Arrangement for Length Expansion Measurement
10.5.1 Measure the width of the specimen in ten places, at PAPER JOINT TAPE
least 1 ft [300 mm] apart, to the nearest ⁄32in. [1.0 mm].
12. Dimensional Stability
Record each measurement.
12.1 Significance and Use:
10.6 Calculation of Results:
12.1.1 This test method is used to determine the lengthwise
10.6.1 Determine the maximum and minimum widths. Cal-
and crosswise expansion characteristics of the paper joint tape
culate the average width.
used to reinforce the joints created in gypsum wallboard
10.6.2 Determine the difference between the maximum and
construction. The degree of correlation between this test and
minimum width by subtraction.
service performance has not been determined.
10.7 Report:
12.2 Sampling:
10.7.1 Reporttheaveragewidth,andthedifferencebetween
12.2.1 Sampling shall be in accordance with Specification
the maximum and minimum width.
C475/C475M.
10.8 Precision and Bias:
12.3 Specimen Preparation:
10.8.1 Precision and bias of this test method have not been
determined. 12.3.1 Cutnotlessthanthreespecimensoftape10to16in.
[250 to 400 mm] long from the roll to be tested.
11. Thickness
12.3.2 Conditionthespecimensforaminimumof16hat72
64°F[22 6 2 °C] and 50 6 2% relative humidity.
11.1 Significance and Use:
11.1.1 This test method is used to determine the average
12.4 Apparatus:
thickness of joint tape. The degree of correlation between this
12.4.1 Steel Rule, Caliper Rule, Cathetometer or other
test and service performance has not been determined.
measuring device capable of resolving 0.005 in. over a
minimum span of 10 in. A metric rule must be capable of
11.2 Sampling:
resolving 0.10 mm over a minimum span of 250 mm.
11.2.1 Sampling shall be in accordance with Specification
12.4.2 Sharp Knife, 4 to 5× Magnifying Glass, Pencil.
C475/C475M.
12.4.3 Glass Container at least 2 ⁄2in. [65 mm] deep and
11.3 Specimen Preparation:
6in. [150 mm] in diameter.
11.3.1 Cut a specimen of tape not less than 12 ft [3.5 m]
12.5 Reagents and Materials:
long from the roll to be tested.
12.5.1 Water, distilled or deionized.
11.3.2 Condition the specimen for a minimum of 24 h as
described in Practice D685.
12.6 Procedure:
12.6.1 Place the conditioned specimens on a flat surface.
11.4 Apparatus:
12.6.1.1 Atabout ⁄2in.[10mm]fromeachendofthepaper
11.4.1 Paper Micrometer having circular faces of 0.25 to
2 2
tape, cut two ⁄2in. [10 mm] long reference marks for the
0.33in. [160to215mm ]inarea.Facesshallbeundersteady
length-wise measurement crosswise of the tape with a sharp
pressure of 7 to 9 psi [50 to 60 kPa].
knife.
NOTE 6—For details see TAPPI T411, except waive Section 7.
12.6.1.2 Place the rule on the tape so that one edge is
11.5 Procedure: centered lengthwise.
11.5.1 Measure the thickness of the specimen in ten places,
12.6.2 Move the rule so that starting mark (A) coincides
between the edges, at least 1 ft [300 mm] apart. Skived areas with the reference mark at one end of the tape. Record the
onthetapeedgesshallnotbeincludedintheareameasuredfor
value atA. Take the reading at the other reference mark. Read
thickness. to the nearest 0.005 in. [0.10 mm]. (See Fig. 3.)
NOTE 7—Skiving is not present on all tapes.
NOTE 8—Measuring from the 1 in. [25 mm] mark and subtracting this
valuemaybeausefulmethodtoobtainanaccuratemeasurement.Reading
11.5.2 Record the thickness to the nearest 0.001 in.
the rule with a magnifying glass of 4 to 5× is recommended.
[0.01mm].
12.6.3 Place the rule across the width of the tape.
11.6 Report:
12.6.3.1 Align the starting mark (B) of the rule with one
11.6.1 Report the average thickness.
edge of the tape. Record the value at B.
11.7 Precision and Bias: 12.6.3.2 Take the reading at the opposite edge of the tape.
11.7.1 Precision as reported in the TAPPI Standard T411 Mark the location of this crosswise measurement by drawing a
states that the within-laboratory repeatability is 1.25% and the 1 ⁄2in. [40 mm] long penc
...