ASTM D351-97
(Classification)Standard Classification for Natural Muscovite Block Mica and Thins Based on Visual Quality
Standard Classification for Natural Muscovite Block Mica and Thins Based on Visual Quality
SCOPE
1.1 This classification covers the determination of commercially available natural muscovite block mica and is intended to be independent of the basic color of the mica or its source.
1.2 Muscovite mica is characterized by having an optical axial angle between 50 and 75° (see Appendix X1); and has a weight loss when heated for 5 min at 600°C not exceeding 0.2% (based on the weight after drying at 120°C).
1.3 The visual system of classifying the quality of natural muscovite mica covered by this specification is based upon relative amounts of visible foreign inclusions such as air bubbles, stains, and spots in combination with relative amounts and types of waviness, as well as other physical properties. In this system, a perfectly clear, transparent, flat specimen of mica is the visual standard of perfection. Increasing amounts of visual defects lower the visual quality, and a total of 13 levels of visual quality are covered by this standard. This method of classification, generally known as the Bengal India System, is purely qualitative and is entirely dependent on personal opinion and judgment.
1.4 The standards for visual quality classification that are covered in this classification are the best commercially available concept of the various qualities and their relative positions. Variations in the methods of using and applying these standards from those herein defined may be specified by the purchaser, or defined by agreement between the supplier and the purchaser.
1.5 Standard size classifications are defined, based upon available usable rectangular areas and the minimum dimensions of the rectangles that the pieces will yield. Precautions to be taken in making thickness measurements are also described.
1.6 This standard covers the following two definite forms of commercial preparation:
1.6.1 Form 1 -Full-trimmed natural block mica, 0.007 in. (0.178 mm) minimum thickness.
1.6.2 Form 2 -Partially-trimmed natural block mica, 0.007 in. minimum thickness.
1.7 The basic color of mica, such as white, ruby, light green, dark green, brownish green, and rum, as well as other colors, and the method of controlling the color and other problems associated with the basic color, are not a part of this classification.
1.8 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
General Information
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Standards Content (Sample)
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An American National Standard
Designation: D 351 – 97
Standard Classification for
Natural Muscovite Block Mica and Thins Based on Visual
Quality
This standard is issued under the fixed designation D 351; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope in. minimum thickness.
1.7 The basic color of mica, such as white, ruby, light green,
1.1 This classification covers the determination of commer-
dark green, brownish green, and rum, as well as other colors,
cially available natural muscovite block mica and is intended to
and the method of controlling the color and other problems
be independent of the basic color of the mica or its source.
associated with the basic color, are not a part of this classifi-
1.2 Muscovite mica is characterized by having an optical
cation.
axial angle between 50 and 75° (see Appendix X1); and has a
1.8 The values stated in inch-pound units are to be regarded
weight loss when heated for 5 min at 600°C not exceeding
as the standard. The values given in parentheses are for
0.2 % (based on the weight after drying at 120°C).
information only.
1.3 The visual system of classifying the quality of natural
1.9 Section 5 is technically identical to procedures specified
muscovite mica covered by this specification is based upon
in ISO 67.
relative amounts of visible foreign inclusions such as air
1.10 Section 6 differs somewhat in procedure from ISO
bubbles, stains, and spots in combination with relative amounts
5972, but data obtained by either should be identical.
and types of waviness, as well as other physical properties. In
1.11 Section 7 is technically identical to procedures speci-
this system, a perfectly clear, transparent, flat specimen of mica
fied in ISO 2185.
is the visual standard of perfection. Increasing amounts of
visual defects lower the visual quality, and a total of 13 levels
2. Referenced Documents
of visual quality are covered by this standard. This method of
2.1 ASTM Standards:
classification, generally known as the Bengal India System, is
D 374 Test Methods for Thickness of Solid Electrical Insu-
purely qualitative and is entirely dependent on personal opin-
lation
ion and judgment.
D 1711 Terminology Relating to Electrical Insulation
1.4 The standards for visual quality classification that are
2.2 ISO Publications:
covered in this classification are the best commercially avail-
ISO 67-1981 Muscovite Mica Blocks, Thins, and Films—
able concept of the various qualities and their relative posi-
Grading by Size
tions. Variations in the methods of using and applying these
ISO 2185-1972 Muscovite Mica Blocks, Thins, and
standards from those herein defined may be specified by the
Films—Visual Classification
purchaser, or defined by agreement between the supplier and
ISO 5972-1978 Mica Blocks, Thins, Films, and Splittings—
the purchaser.
Measurement of Thickness
1.5 Standard size classifications are defined, based upon
available usable rectangular areas and the minimum dimen-
3. Terminology
sions of the rectangles that the pieces will yield. Precautions to
3.1 For definitions of terms relating to mica refer to Termi-
be taken in making thickness measurements are also described.
nology D 1711, Part III.
1.6 This standard covers the following two definite forms of
3.2 Terms Specific to This Standard:
commercial preparation:
3.2.1 “A”—a series of rulings or striations intersecting at an
1.6.1 Form 1—Full-trimmed natural block mica, 0.007 in.
angle of about 60°.
(0.178 mm) minimum thickness.
3.2.2 blocks—mica thickness of 0.007 in. (0.178 mm)
1.6.2 Form 2—Partially-trimmed natural block mica, 0.007
minimum thickness, full-trimmed, unless otherwise desig-
nated.
This classification is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.19 on Dielectric Sheet and Roll Products. Annual Book of ASTM Standards, Vol 10.01.
Current edition approved Sept. 10, 1997. Published February 1998. Originally Available from American National Standards Institute, 11 W. 42nd St., 13th
e1
published as D 351 – 32. Last previous edition D 351 – 85 (1994) . Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 351
3.2.3 buckle—one or more large depression(s) and eleva- of the rectangle (maximum rectangle for full-trimmed, maxi-
tion(s). mum rectangle of designated quality for half-trimmed) having
3.2.4 cracks—irregular fractures within the crystal that may at least the minimum dimension of one side for the specified
be natural or may arise from blasting, rough handling, etc. grade. The area within such a rectangle shall meet the
3.2.5 full-trimmed mica—mica trimmed on all sides with all requirements of the quality specified by the purchaser as listed
cracks, reeves, and cross-grains removed. in Table 1.
3.2.6 haircracks or hairline cracks—minute, irregular 5.4 Method of Grading for Size—The Standard ASTM
cracks that are barely noticeable until mica is split into films, Chart shown in Fig. 1 shall be used for grading natural block
resulting in production of torn films. and thins, muscovite mica according to size. In grading natural
3.2.7 reeves or cross grains—tangled laminations giving block mica and thins for size, all dimensions apply to the
imperfect cleavage, that results in tears or breaks during smaller surface measured from the foot of the bevel-trimmed
splitting. edge. The specimen to be graded shall be laid upon the chart so
3.2.8 ribboned or rules mica—mica that breaks into narrow that it covers point O and has its maximum and minimum
strips because of parallel fractures. dimensions extending along and covering lines OA and OB,
3.2.9 ribs or ridges—crenulations in the form of steps. respectively. The specimen shall be shifted until the usable area
3.2.10 ripple—multiple short waves. completely covers the largest rectangle, determined by a
3.2.11 stains—stains arise from foreign materials, resulting diagonal extending from point O to or beyond a point on any
in a partial or total loss of transparency. They may be in the of the curves. The number of the curve at the greatest distance
form of specks or patches of appreciable area for example, from O cut by the diagonal of the rectangle designates the
slight stain, “vegetable” stain, clay stain, black stain, red stain, grade of the specimen.
black speckled, light dot or spot, black, red or green dot or spot,
6. Thickness of Block Mica
etc. (see “inclusions” in Terminology D 1711).
6.1 Measure the thickness with a micrometer as specified in
3.2.12 stones and stone holes—small embedded crystals or
Test Methods D 374. In determining thickness of mica that
holes resulting from them.
must be kept within small permissible variations, or where two
3.2.13 thins—knife-dressed mica, 0.002 in. (0.05 mm) to
or more specimens are to be measured at once, use Method A
less than 0.007 in. (0.18 mm) in thickness. They may be
of Test Methods D 374. Where the maximum accuracy is not
classified as follows:
required, Method B may be used.
3.2.13.1 Thins, 0.002 to 0.004 in. (0.05 to 0.10 mm), and
6.2 Because of the abrasive nature of mica, test the mi-
3.2.13.2 Thick-thins, 0.004 to 0.007 in. (0.10 to 0.18 mm).
crometer frequently for conformity to the requirements speci-
3.2.14 unmanufactured mica—commercial form of mica
fied in Test Methods D 374. Clean the anvil and spindle as
known as blocks, thins, films, and splittings, as described.
frequently as necessary to prevent the accumulation of mica
3.2.15 waves—alternate elevations and depressions that
dust on the surfaces and to preserve the accuracy of the
may be classified as slight, medium, or heavy.
measurements. To clean, close the micrometer lightly on a
4. Significance and Use
clean sheet of bond paper and move the paper between the
surfaces.
4.1 The properties included in this standard are those
required to control the visual quality, usable area, thickness, 6.3 Be careful, when moving from one measurement loca-
tion to another, to maintain the surfaces of the anvil and spindle
hardness, and stiffness.
parallel to the surfaces of the specimen at all times, so as to
5. Grading for Size
avoid scratching the mica and accumulating mica dust under
5.1 Full-Trimmed—All full-trimmed mica blocks and thins the micrometer surfaces, thereby causing false readings.
shall be fully trimmed to remove all cracks, holes, reeves, and
TABLE 1 ASTM Grade Sizes of Muscovite Uncut Mica Block and
cross-grains according to the quality desired. As far as possible,
Thins
all marginal cracks should be removed by recutting. The
Minimum
average area of the pieces for Grade 4 and larger shall be not
Area of
Dimen-
Minimum
more than 1.54 times the average area of the largest usable
ASTM
sion of
Rectangle
Grade
rectangles. This would constitute a minimum yield of 65 %. One Side
Sizes
For Grades 5 and smaller, the average area of the pieces shall
Equiva- Equiva-
in. in.
lent, cm lent, mm
be not more than two times the average area of the largest
usable rectangles. This would constitute a yield of 50 %. OOEE Special 100 650 4 100
OEE Special 80 520 4 100
5.2 Half-Trimmed—For half-trimmed mica, follow the
EE Special 60 390 4 100
grading described in 5.1 for trimmed sides with no cracks
E Special 48 310 4 100
extending from the trimmed sides, except for sizes 6 and 5 ⁄2 on A-1 (Special) 36 235 3 ⁄2 89
No. 1 24 155 3 76
which only side must be trimmed free of cracks. On the
No. 2 15 97 2 51
untrimmed sides, no defects of the designated quality are
No. 3 10 65 2 51
acceptable within the minimum rectangle of the designated No. 4 6 40 1 ⁄2 38
No. 5 3 20 1 25
grade.
1 1 7
No. 5 ⁄2 2 ⁄4 15 ⁄8 22
5.3 Natural Block and Thins—Natural block and thins,
No. 6 1 6.5 ⁄4 19
muscovite mica shall be graded for size according to the area
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 351
NOTE 1—This chart may be readily extended for Grades OOEE Special, OEE Special, EE Special, and E Special, using the information given in Table
1 of ASTM Specification D 351.
FIG. 1 ASTM Chart for Grading Natural Muscovite Block and Film Mica
7. Classification of Visual Quality of Block Mica 7.1.10 V-9 Black Dotted
7.1.11 V-10 Black Spotted
7.1 The classification of the visual quality of muscovite
blocks and thins shall fall into the following thirteen catego-
7.1.12 V-11 Black Stained
ries:
7.1.13 V-12 Black/Red Stained
7.1.1 V-1 Clear
7.2 The classification of the visual quality of block mica
7.1.2 V-2 Clear and Slightly Stained
shall be judged in accordance with the requirements specified
7.1.3 V-3 Fair Stained
in Table 2 using the visual descriptions given.
7.1.4 V-4 Good Stained
7.1.5 V-5 Stained A Quality
8. Keywords
7.1.6 V-5.1 Stained A1 Quality
8.1 Bengal India System; block; classification; foreign in-
7.1.7 V-6 Stained B Quality
7.1.8 V-7 Heavy Stained clusions; form; grading; muscovite mica; size; thins; visual
7.1.9 V-8 Densely Stained quality
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 351
A,B
TABLE 2 Quality Classification of Muscovite Block and Thins Based on Visual Properties
Air Inclusions Waviness Hardness
Visual
Quality
Classification
V-1 Clear 333333333 = 3333 = 333333333333
C
V-2 Clear = = 3333333 = = 333 = 333333333333
and Slightly
Stained
C
V-3 Fair = = = 333333 = = = 33 = 333333333333
Stained
C D
V-4 Good = == = 33333 ==== 3 = 333333333333
Stained
E C
V-5 Stained ==== = 33 = 3 ==== 3 = 333333333333
A Quality
F G C
V-5.1 Stained ==== = 3= = 3 ====== 333333333333
A1 Quality
H H H C
V-6 Stained ===== 3 = = = ====== 3 3 = 333333333
B Quality
H I
V-7 Heavy ===== 3 = = 3 ====== 3 3 = 333333333
Stained
I I I I
V-8 Densely ===== = = = = ====== S ==== 3 ======
Stained
J
V-9 Black ===== 3 = = 3 ==== 3 = 333333333333
Dotted
C
V-10 Black ===== 3 = = 3 ==== 3 = 3 3 = 333333333
Spotted
H
V-11 Black ====== = ====== 3 = 33333333333 =
Stained
H C
V-12 Black/ ====== = ====== 3 = S 3= 333333333
Red Stain
A
Symbols:
=—Permissible
3—Not permissible
S—Permissible only if specified
Few and tiny in one-fourth of usable area.
B
In one-half usable area
C
Slight
D
In two-thirds usable area
E
Uniformly distributed
F 2
1 1
Not heavily concentrated over more than an area equivalent to ⁄4 in. square (6.4 mm square) for grade 5 and up and over more than an area equivalent to ⁄8 in. (3.2
mm ) for Grade 5 ⁄2 and lower
G
Not exceeding two specks within the usable area
H
Medium
I
Heavy
J
Dispersed black dots
Note 1—The visual properties of block mica usually are judged under the following light conditions:
For stains and inclusions—Transmitted daylight or its equivalent.
For air inclusions—Reflected daylight or its equivalent.
For waves, buckles, ridges, etc.—Reflected daylight or its equivalent where distortion of parallel and vertical lines of reflected image, such as a window frame, can
be judged.
Note 2—The hardness or mechanical properties of muscovite mica are usually judged by a sharp, clear ring when mica is dropped on a hard surface.
Note 3—Muscovite mica occurs in various colors which are more pronounced the thicker the block. Some typical colors are ruby, white, light green, rum, etc.
Note 4—Cracks, tears, stones, or pin holes are judged by transmitted daylight or equivalent.
Note 5—Rigidity is judged by the relative stiffness when flexing with the fingers.
Note 6—See Section 3 for definition of terms used in Table 2.
Note 7—The following are verbal descriptions of the classification of muscovite blocks and thins, judged in terms of requirements of Table 2:
V-1 Clear—Hard, of uniform color, flat, free from all stains and foreign inclusions, waves, cracks, buckles, and other similar defects.
V-2 Clear and Slightly Stained—Hard, of uniform color, nearly flat, free from all vegetable and mineral stains, cracks, buckles and other similar defects, and foreign
inclusions except for a few tiny air inclusions in not more than one-f
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