N6SIR 74-519

Photometric Tests of Vehicle

Glazing Materials

W. A. Hall, E. L. Walters, l.-Nimeroff, and C. A. Douglas

Illuminating Engineering Group

Optical Radiation Section

Heat Division

Institute for Basic Standards

National Bureau of Standards

Prepared for Department of Transportation

National Highway Traffic Safety Administration

under

Inter Agency Agreement

No DOT<HS-185^^99IA

NBSIR 74-519

PHOTOMETRIC TESTS OF VEHICLE

GLAZING MATERIALS

W. A. Hall, E. L. Walters, I. Nimeroff, and C. A. Douglas

Illuminating Engineering Group

Optical Radiation Section

Heat Division

Institute for Basic Standards

National Bureau of Standards

Prepared for Department of Transportation

National Highway Traffic Safety Administration

under

Inter Agency Agreement

No D0T^HS48 5 3 599IA

U. S. DEPARTMENT OF COMMERCE. Frederick B. Dent. Secretaiv

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Oirvctor

Preface

Certain commercially available equipment, instruments

and materials are identified in this report to specify adequately

the experimental procedures used and the materials to which the

data obtained apply. In no case should such identification be

inferred as an evaluation by the National Bureau of Standards of

the suitability of the product for its intended purpose.

CONTENTS

Page

Abstract 2

1. Introduction 3

2. Spectral Characteristics of Windshields and Paints 3

3. In-Laboratory Transmit tance Measurements 16

4. Glazing Materials Tested 16

5. In-Laboratory Test Procedure 16

6. In-Laboratory Results 19

7. Discussion 30

LIST OF FIGURES

Figure 1. Spectral Transmittance of Automobile Glazing W710S 4

Figure 2. Spectral Transmittance of Automobile Glazing W710ST 5

Figure 3. Spectral Transmittance of Automobile Glazing W769C 6

Figure 4. Spectral Transmittance of Automobile Glazing W769S 7 Figure 5. Spectral Transmittance of Automobile Glazing W769ST 8

Figure 6. Spectral Transmittance of Automobile Glazing Sierracin W/S . 9

Figure 7. Spectral Reflectance of Automobile Paint Metallic Blue 10

Figure 8. Spectral Reflectance of Automobile Paint Red 11

Figure 9. Spectral Reflectance of Automobile Paint Greenish Yellow ... 12

Figure 10. Spectral Reflectance of Automobile Paint Metallic Green .... 13

Figure 11. Spectral Reflectance of Automobile Paint Light Gray 14

Figure 12. General View of In-Laboratory Photometric Equipment 17

Figure 13. Variation of Transmittance with Incidence Angle of Glazing

Material: W769, Shaded, XU 1 20

Figure 14. Variation of Transmittance with Incidence Angle of Glazing

Material: W799, Shaded, XU 3A 21

Figure 15. Variation of Transmittance with Incidence Angle of Glazing

Material: Electrically Heated, 3D 22

Figure 16. Variation of Transmittance with Incidence Angle of Glazing

Material: B4625, Clear, AS2-AT 23

Figure 17. Variation of Transmittance with Incidence Angle of Glazing

Material: B4625, Tinted, AS2-CY 24

Figure 18. Variation of Transmittance with Incidence Angle of Glazing

Material: D 4620, Clear, AS2-UT 25

Figure 19. Variation of Transmittance with Incidence Angle of Glazing

Material: D 4621, Tinted, AS2-TY 26

TABLES

Table 1. Luminous Transmittance of Automobile Glazing Materials (t) , Luminous Reflectance of Automobile Paints (3) and Chromaticity

Coordinates (x, y) for Source A (2856K) Supplied to the

Environmental Engineering Section 15

Table 2. Description and Number of Samples for In-Laboratory

Measurements 18

Table 3. Variation of Transmittance with Angle 27

Table 4. Variation of Transmittance (%) of Automobile Glazing, W799-3E,

with Variation of Parameters 28

Table 5. Variation of Transmittance (%) of Electrically Heated

(Sierracin) Glazing with Variation of Parameters 29

1
ABSTRACT

Measurements were made on the spectral transmit tance of representative vehicle glazing materials and spectral reflectance of

representative automobile paints. Colorimetric data were derived

from these spectral measurements.

By varying the instrumental parameters of the in- laboratory

procedure described in NBS Report No. 10902 for measuring the transmittance of glazing materials, errors in transmittance were obtained and

were evaluated. The standard deviation of the transmittance measurements was less than 0.01 except at incidence angles of 70° where it was about 0.02.

2
1. Introduction

The work described in the report was performed under Inter

Agency Agreement No. DOT-HS-185-3-599 lA dated February 15, 1973,

between the National Highway Traffic Safety Administration and the

National Bureau of Standards. This project is a continuation of

the Inter Agency Agreement No. DOT-HS-020-2-312 lA dated March 30,

1972, the results of which were given in NBS Report 10 902, "Photometric Tests of Vehicle Glazing Materials", dated August, 1972. The

objectives of this follow-on project are (1) to determine if

additional samples of certain types of tinted, IR- absorbing windshields have the very high light transmission characteristics found

in the original project and (2) to conduct additional laboratory and

in-vehicle tests to provide a broader data base.

The Inter Agency Agreement of 197 3 also describes an additional

objective, to determine the heat load differences from sunlight between

tinted and untinted glazing materials. Interior temperatures under

service conditions of a car equipped with a clear windshield were compared to a similar car with a tinted windshield by the Temperature

Section of the National Bureau of Standards. The comparison has been

reported in NBS Report IR 74-533, "Influence of Windshield Tint on the

Temperature in Automobile Passenger Compartments", by W. S. Hurst and

M. G. Scroger.

2. Spectral Characteristics of Windshields and Paints

Measurements were made of the spectral transmittances of samples

of glazing materials used in the first series of tests, a sample of an electrically heated windshield supplied for the second series of tests

and the spectral reflectance of several automobile paints to obtain

data for possible use in a theoretical heat-load study. The spectral

transmittance of the glazing materials (including the electrically heated

Sierracin windshield) are shown in Figures 1 through 5 and the spectral

reflectance of the automobile paints are shown in Figures 7 through 11. The

chromaticity coordinates for the luminous transmittance and reflectance

samples are shown in Table 1.

3



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Table 1. Luminous Transmit tance of Automobile Glazing Materials (t) , Luminous Reflectance of Automobile Paints (3) and Chromaticity Coordinates (x, y) for Source A (2856K) Supplied to

the Environmental Engineering Section.

Automobile Chromaticity Coordinates

Materials Sample* X y T(%)

Glazing W 710S (1972) 0.432 0.418

(1) (2)

73,5 73.7

W 710ST (1972) .386 .344 7.3

W 769C (1972) .445 .410 88.2 88.0

W 768S (1972) .440 .414 82.0 80.4

W 768ST (1972) .402 .345 9.9

Electrically Heated

AT 7 13,1 —

3(%)

Paint Metallic Blue 0.347 0.359 14.6

Red .613 .358 19.9

Greenish Yellow .495 .468 50.6

Metallic Green .456 .443 24.8

Light Gray .454 .414 61.6

* Year sample obtained in parenthesis.

(1) From spectrophotometric data.

(2) Reported in NBS Report No. 10902.

15
3. In-Laboratory Transmittance Measurements

The measurement system for the transmittance measurements was the same as described in NBS Report 10902, Section 2, "Design of the Measuring

System". Figure 12 shows the in-laboratory photometric equipment for

measuring the transmittance of the glazing materials.

4. Glazing Materials Tested

The vehicle glazing materials measured in the follow-on were

purchased from the local distributors of two different manufacturers.

A Sierracin windshield (electrically heated glass) was loaned to NBS by

the Ford Motor Co., Glass Technology Division, for light transmittance

measurements. This sample has been returned to the Ford Motor Company.

Table 2 gives the type and number of samples and industry trade number

for the glazing materials tested.

5. In-Laboratory Test Procedure

The in-laboratory test procedure was as described in Section 3.1.2,

"In-Laboratoiry Test Procedure", of NBS Report 109Q2. The following procedures for measurement are extracted from that report.

a. The light source and photometer were turned on and

allowed to stabilize for a minimum of 30 minutes. The

. , voltage was monitored with a 0.25% dynamometer voltmeter

and regulated to 0.1%.

b. With the photometer aligned on the center of the

liaminous area of the source, and the test sample removed,

the sensitivity of the photometer was adjusted to give

a full scale reading (100%) on the X-Y recorder chart.

The goniometer table was rotated about a horizontal

axis through 90°, giving a 100% trace vs. vertical angle.

c. Prior to the start of the test, the effect of stray

light was determined. The stray light reading with the

room lights on was found to be less than 0.5% of the full

scale reading. Since the tests were made with the room

lights off, the effects of stray light were negligible.

d. The test specimen was then mounted on the goniometer,

aligned so that the photometric axis was perpendicular to

the tangent plane of the windshield at the point of

intersection with the specimen, and then cleaned.

e. The goniometer was then rotated about its horizontal

axis through 90°, giving the measurement of transmittance

as a function of the angle between the normal to the

specimen and the photometric axis. The transmittance

was measured at three additional points on each test

specimen normal (0°) to the specimen, to determine the

uniformity of the transmittance.

16
FIGURE 12. GENERAL VIEW OF IN-LABORATORY PHOTOMETRIC EOUIPMENT

a. Light Sourcei b. Goniometeri c. Sample Frame

d. Sample Windshield) e. Photometer Receiver)

Photometric Indicator and Recorder

NBS REPORT NO. 74 519

17
Table 2. Description and Number of Samples for In-Laboratory Measurements

Number Industry DESCRIPTION Tested Trade No.

Windshield, tinted

Windshield, tinted

Back window, tinted

Back window, clear

Side window, front, tinted

Side window, front, clear

Windshield, electrically heated

5 W769

5 W799

2 B4625

2 B4625

2 D4620

D4621

2 D4620

D4621

1

18
6. In-Laboratory Results

6.1 Variation of Transmit tance with Incidence Angle

The results of the transmit tance measurements of one sample

from each group as well as for the electrically heated windshield are shown in Figures 13-19.

The complete tabulation of the results of the measurements

is given in Table 3.

In addition to the measurements of transmittance shown in

Table 3, two of the windshield samples, W-799-3E and the Electrically

Heated, were measured several times to determine the precision

(repeatability) of the measurement. In addition, different

parameters of the measurement system were varied to determine

the sensitivity of the measurement system. The changes were

(1) the source voltage was reduced from 116.0 V to 60.0 V,

(2) a 3/8 inch diaphram was installed on the photometer lens,

(3) the distance from the source to the photometer was varied

from approximately one-half the normal distance (approximately

10 ft.) to twice the distance, (4) the photometer was aligned

at an angle of about 1° from the normal (perpendicular) to the source instead of normal.

The results of repeated transmittance measurements and

measurements with variations of the parameters are given in

Tables 4 and 5. The measurements at various distances and at

a 1° deviation from normal incidence on windshield W799-3E were

within the spreads of the measurements given in the Table 4.

6.2 Precision of Measurements

19
INCIDENCE ANGLE (DEPREES)

FIGURE 13. VARIATION OF TRANSMITTANCE WITH INCIDENCE ANGLE

OF GLAZING MATERIAL: V/769i SHADED. XU 1

N3S REPORT 74 519

20
FIGURE 14. VARIATION OF -mANSM I TTANCE WITH INCIDENCE ANGLE

OF GLAZING MATERIALS: W799, SHADEDf XU 3A

NBS REPORT NO. 74 519

21

i
100

INCIDENCE ANGLE (DERREES)

FIGURE 15. VARIATION OF TRANSMITTANCE WITH INCIDENCE ANGLE

OF GLAZING MATERIAL: ELECTRICALLY HEATED. 3D

NBS REPORT NO. 74 519

22
FIGURE 16. VARIATION OF TRANSMITTANCE WITH INCIDENCE ANGLE

OF GLAZING MATERIAL: B4625, CLEAR. AS2-AT

NBS REPORT No. 74 519

23
100

INCIDENCE ANRLE (DERREES)

FIGURE 17. VARIATION OF TRANSMITTANCE WITH INCIDENCE ANKLE

OF GLAZING MATERIAL: BA625, TINTED. AS2-CY

NBS REPORT NO. 74 519

24
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FIGURE 18. VARIATION OF TRANSMITTANCE WITH INCIDENCE ANGLE

OF GLAZING MATERIAL: D 4620i CLEAR, AS2-UT

NBS REPORT NO, 74 519

25
FIGURE 19. VARIATION OF TRANSMITTANCE WITH INCIDENCE ANGLE

OF GLAZING MATERIAL: D4621, TINTEDi AS2-TY

NBS REPORT No. 74 519

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7. Discussion

The slight rise in transmission of the glazing materials, which

was shown in the data in NBS Report 10902, between 0° and 20", was investigated during this follow-on project. It was found that this

rise was caused not by the glazing materials, but by a slight anomaly

in the photometer used for the measurement. This photometer error was eliminated during the measurements performed for this project.

The loss of precision at the 70* incidence angle results from small

deviations in initial alignment which have a greater effect at large

incidence angles where the change of transmittance with angle is large.

In the repeated measurements of transmittance, the windshields were

aligned using the care that was expected of a careful tester in the

field. Sophisticated techniques and equipment, such as lasers, were

not used. The results, therefore, are indicative of the precision ex- pected from field measurements.

30
U S. DEPT. OF COMM

BIBLIOGRAPHIC DATA

SHFET

1. PriM.K ATION OR RHPORT NO. NBS 74 519

2. (lov't Accession

No.

3. Rfr ipunt 's At (, (• s . i,,n Ni

4. 1 1 1 LI AM) SUH riTLl-;

Photometric Tests of Vehicle Glazing Materials

5. Pub! It .11 ii)n Daif

6. Pr rform ing ( Ifj^.ui i /ai inn ' odt

7. AL'THOR(S)

W. A. Hall, E. L. Walters, I. Nimeroff, and C. A. Douglas

8. Perlorniinj; ('iLTin. Rc-p(irt No.

9. PKKFOR.MINC ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Pro|ect/Ta.si</Work Unit No.

11. (.ontrac i/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Dept. of Transportation

National Highway Traffic Safety Administration

Washington, D. C. 20590

13. Type of Report & PrrioiJ

( ov c r e d

14. Sponsoring Agency t ai\v

15. SUPPLEMENTARY NOIES

16. ABSTRACT (A 200-word or less factual summary of most si^ificant informatiort. If document includes a significant

bibliography or literature survey, mention it here.) Measurements were made on the spectral transmittance of representative vehicle

glazing materials and spiectral reflectance of representative automobile paints. Colorimetric data were derived from these spectral measurements.

By varying the instrumental parameters of the in-laboratory procedure described in

NBS Report No. 10902 for measuring the transmittance of glazing materials, errors in

transmittance were obtained and were evaluated. The standard deviation of the transmittance measurements was less than 0. 01 except at incidence angles of 70° where it was

about 0. 02.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Automobilc paint colors; automobilc Windshield color; photometric

tests; spectral reflectance; spectral transmittance; transmittance variation; vehicle glazing

materials.

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! For Official Distribution. Do Not Release to NTIS

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L Order l-'rom National Technical Information Service (NTIS)

Springfield, Virginia 22151

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UNCLASSIFIED

21. NO. OF PAGES

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