NATIONAL BUREAU OF STANDARDS REPORT

4295

SPECTROPHOTOMETRIC

AND

COLORIMETRIC

ANALYSIS

OF

SEVENTEEN GLASS FILTERS

DUPLICATING THE

RELOCATED AND RESPACED

UNION COLOR SCALE

FOR

LUBRICATING OIL AND PETROLATUM

FOR

ASTM COMMITTEE D-2

RESEARCH DIVISION IX

SUBMITTED BY HELLIGE, INC.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

by

John C a Schleter
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

0201-20-0203 September 1955 4295

SPECTROPHOTOMETRIC

AND

COLORIMETRIC

ANALYSIS

OF

SEVENTEEN CLASS FILTERS

DUPLICATING THE

RELOCATED AND RESPACED

UNION COLOR SCALE

FOR

LUBRICATING OIL AND PETROLATUM

FOR

ASTM COMMITTEE D-2

RESEARCH DIVISION IX

SUBMITTED BY HELLIGE, INC.

by

John Co Scirleter

Photometry and Colorimetry Section

National Bureau of Standards

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, reprint

unless permission Is obta 25, D.C. Such permissl

cal ly prepared If that a

Approved for public release by the

director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

irt, is prohibited

irds, Washington

has been speclfifor its own use.

Spectrophotometric

and

Color imetrie

Analysis

of

Seventeen Glass Filters

Duplicating the

Relocated and Respaced

Union Color Scale

for

Lubricating Oil and Petrolatum

for

ASTM Committee D-2

Research Division IX

Submitted by Hellige, Inc.

ABSTRACT

At the request of Research Division IX on Color, of ASTM

Committee D-2 on Petroleum Products, a spectrophotometric and

colorimetric analysis of a set of seventeen glass filters,

submitted by Hellige, Inc. , has been carried out. These

filters were manufactured to the specifications given in NBS

Report 2012, modified in regard to the last two filters by

letter to Research Division IX. From the data of this analysis

it is found that all of the seventeen filters now pass the

required tolerance limits, both for chromaticity and transmittance.

I. INTRODUCTION

In 1950, the National Bureau of Standards completed- the

derivation of a relocated and respaced Union color scale1, INBS

Research Paper RP2103) to replace the original Union scale 2

. The glass filters of the original Union color scale were

measured by the Bureau in 19293*

In the attempt to obtain glass filters meeting the

specifications given in RP2103 , Hellige, Inc. was contacted

early in 1951 s and agreed to submit to the Bureau, at the

request of Research Division IX, twelve glass filters which

were to be close matches to the original Union color scale.

From the data of spectral transmittance of the components of

these filters, the author formulated the designs for sixteen

filters to satisfy the specifications for the relocated and

respaced color scale. These design data were given in NBS

Report 20124%

Using these design data, Hellige, Inc. prepared a set

of seventeen filters (sixteen filters of the color scale and

one modified filter) and submitted them, through Research

Division IX, to NBS in June 1953 , to ascertain whether these
.

'

, I

.

'
2 -

filters complied with the specifications of RP2103* The

filters were submitted in uncemented component form with

the exception of components whose thicknesses were greater

than that of the stock glasses • For these components

several pieces of the same type of glass were submitted in

cemented form*

II* SPECTRQPHOTOMETRIC MEASUREMENTS

The measurements of spectral transmittance of the

glasses were made on a General Electric recording spectrophotometer^^, equipped with slits equivalent to approximately

10 millimicrons of spectrum for the spectral region LfiO to 750

millimicrons * These measurements were made on the filters by the

procedure given in Section III* pages 2 and 3? NBS Report 2012*

The components of the filters were combined to give results

equivalent to cemented filters by using a film of glycerine

between individual components to remove the light losses due

to reflections at the surfaces* When the spectrophot ometric

data were reduced and the colorimetric analysis completed, it

appeared that half of the filters failed to pass the specifications of RP2103 . These results were given in NBS Report

2935 7 -Spectrophot ometric measurements were then made on the

individual components, in order to obtain data from which to

make the modifications to the filters* Measurements for each

filter were made on the same spectrophot ometric graph sheet,

both for the separate components and also for the combined

filter with a glycerine film between components* These

measurements served as a check on the previous measurements*

By using the data of these measurements, modifications

of the designs were attempted* It was found that the results

obtained by computation, from the individual components, of

the chroma ticity coordinates and luminous transmittances of

the filters which appeared to fail, did not agree with the

data obtained from direct measurements of the combined filters

with a glycerine film between components*

The discrepancies were believed to be caused by the

following: - (1} incomplete coverage of the glycerine film

between the individual components, (2) the reduction in the

sensitivity of measurements for low values of transmittance

when the twc supplementary lenses were used, and (3) the

difficulty in reproducing the same positioning of the two

lenses in the optical path of the spectrophotometer for

successive measurements*
.0

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A new supplementary lens system was developed using

only one double convex menieus lens of approximately +3

diopters, placed before the decenter ed lens of the spectrophotometer, and large enough to intercept both beams. This

supplementary Ions was mounted in a blackened brass ring which

fitted in the decentered lens mount of the spectrophotometer.

A new sample holder was made from blackened brass to both hold

and position the sample and also serve as a diaphragm in the

sample compartment of the spectrophotometer. No diaphragm

was used on the comparison side of the instrument.

Tests of this new single supplementary lens system were

made by using glass samples large enough to be measured with

and without the -supplementary lens system and having spectral

transmittances similar to the components of the filters of the

color scale. Measurements were also made on these same glasses

by means of a Beckman Model DU quartz spectrophotometer. The

analysis of these data showed good agreement, within the

experimental error, between measurements made with and without

the single supplementary lens system in place. Furthermore an

improved sensitivity of measurement for low values of transmittance seems to have resulted from the use of this single

supplementary lens system. For these reasons, the single

supplementary lens system was used for the remainder of the

measurements.

The procedure as given in Section III, pages 2 and 3,

NBS Report 2012, was further modified by the omission of the

measurement of the "True 100% Curve", as the "Lens 100% Curve"

only was used for the calibration of the spectrophotometric

graph sheets.

The components of the eight filters, which seemed to fail

the specifications, submitted in cemented form were taken

apart and cleaned previous to making further measurements. The

spectral transmittances of all of the filters, whether or not

they appeared to fail or pass the specifications were remeasured by the new procedure.

Subsequently, the components of the filters were cemented

together with Canada balsalm to form the set of 1? filters.

Measurements of spectral transmittance were then made on the

cemented filters. The procedure used for these measurements

was the same as that used for the components, with the addition

of a series of measurements made with a "X5" cam, which gives

0% to 20% for full scale of graph sheet, rather than 0% to 100%

full scale as obtained with the "normal" cam.
V

“
-4-

This series of measurements was made in an attempt to

obtain improved values of spectral transmittance of the

cemented filters in the range between 0$ and 2$.

III, SPECTRQPHQTQMETRIC RESULTS

The spe ctrophotometric curves of each graph sheet were

read at 10-millimicron' intervals between 400 and 750 millimicrons,

corrections being made for wavelength errors by comparing the

known wavelengths of minimum transmittance of a Corning 512

didymium glass with those recorded on the graph sheets. The

photometric scale was corrected, as previous described, by

means of the !t Lens 100$ Curve”, and the zero curve.

When the ”X5” cam was used with the supplementary lens

system, the stray light in the optical system of the instrument

caused the zero curve to be recorded on the graph sheets at

approximately 0,2$ rather than at 0,0$, with a slight decrease

towards longer wavelengths. The values of spectral transmittance

of this ”X5 n cam zero curve were read and extrapolations made

for the remainder of the visible spectrum in which the filters

were transmitting. These values of the ”X5 Tt cam zero curve were

then subtracted from the values of spectral transmittance of the

filters in the usual way for the zero correction.

It was foilnd for very low values of transmittance (0.0$ to

about 0.2$) that the "normal” cam data generally indicated lower

values than the ”X5 n cam data. For this transmittance range the

”X5” cam data were adopted. In the transmittance range between

about 0.2$ and 20,0$ the "normal” cam and ”X5 Tf cam data were

found to be in generally good agreement; and for this transmittance range an average of the two sets of data were used.

Above 20.0$, of course, only "normal” cam data were available.

IV. COMPUTATION OF SPECTRAL TRANSMITTANCE FROM COMPONENT DATA

The data of spectral transmittance of the individual

components of the filters were combined by means of Equation

(10} , page 5> NBS Report 2012, to obtain the "computed” spectral

transmittances of the various filters. In performing the

computations, four decimals were maintained for Filters B(0.5)

through L(5°5) and six decimals were maintained for Filters

M(6.oT through Q(£.0), for reasons given below.
, . , .
-5-

Vo COLORIMETRIC RESULTS

The values of spectral transmittance for each filter were

converted to values of luminous transmittance, Y, and chromaticity

coordinates (x, y), in accord with the 1931 CIE standard observer

and coordinate system for colorimetry^ for CIE Source C

(representing average daylight ) 0 The values of the chromaticity

coordinates (x,y), were then transformed into the uniform

chromati city-scale (UCS) system9 for correlation with the

previous data, by means of the equations given on page 3 * NBS Report 2935.

As in the computations of spectral transmittance of the

filters from the data obtained from the individual components,

four decimals were maintained for the computations of chromaticity

coordinates (x,y) of Filters B(0. 5) through L (5.5)? and six

decimals were maintained for the computations for Filters M( 6 .Q)

through Q(6.0), to eliminate significant errors of rejection in

the dark and red end of the scale • All of the computations of

the chromaticity coordinates (r,b) were made with four decimals,

since in the final analysis, only 3 decimals were reported.

VI. MODIFICATIONS TO DESIGN DATA

As a result of the measurements made on the components and

the cemented filters, it was found that only the last two filters

of the scale. Filters P(?o5) and Q(3.0), failed to pass the

specif ic at ior< s, The design data for these two filters were

modified by increasing the thickness of the red component of each

filter as follows: Filter P( 7. 5 ) ? O .663 mm rather than 0.45y mm;

and Filter Q(3.0), 1.132 1111,1 rather than 0.87i mm. These modified

thicknesses were reported to Research Division IX at the meeting

of October 4? 19543 and also by letter to the secretary on

November 30, 1954.

The new components were received in February, 1955 ? and

measurements made on them later in the year.

VII. ADOPTED VALUES

The values of the chromaticity coordinates (r,b), and

luminous transmittance, I, adopted for the set of seventeen

glass filters of the color scale were those obtained from

values of spectral transmittance computed from the components

rather than from the measured values obtained directly from the

cemented filters because the precision of the results was found

to be greater. The values of the chromaticity coordinate, r,

for Filters B(0.5) through 0(7*6), obtained by the two methods,
’

.

,

• '

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generally agree to within 0.001 for twelve of the fifteen

filters, the greatest deviation being 0.003 for Filter L ( 5 - 5 )

No measurements were made on cemented Filters P(7.5) and Q(8.0),

since measurements made directly with similar cemented filters

were found to be not reproducible.

The adopted values of the chromaticity coordinates (r,b),

and the luminous transmittances, Y, together with the limits

for each filter, are given in Table I.

Figure 1 shows the chromaticity coordinates, in the UCS

system, of the duplicate filters of the relocated and respaced

Union color scale. In this figure it should be noted, the red

axis, r, has been divided into three sections. The large open

circles indicate the chromaticity tolerances.

Figure 2 shows, on a square-root scale, the luminous

transmittances, Y, plotted against Union number. The open

circles of varying size indicate the transmittance tolerances.

The tolerance limits and luminous transmittances of Filters

P ( 7 • 5 ) and Q(&.0) are plotted on an enlarged ordinate scale

at the right-hand side of the figure.

From Table I and Figures 1 and 2, it can be seen that all

seventeen of the filters pass the chromaticity specifications

as given in RP2103 . The luminous transmittances of all of the

filters fall within the transmittance specifications, with the

exceptions of Filters H(3.5) and J(4*5) which are considered to

pass even though the value of transmittance are the maximum

allowed in the specification. Note that the viewing conditions

present in the ASTM Union Colorimeter require strict adherence

to the chromaticity tolerances, but that the transmittance

tolerances are probably more strict than necessary.

VIII. SUMMARY

At the request of Research Division IX on Color, ASTM

Committee D-2 on Petroleum Products, a spectro photometric and

colorimetric analysis of a set of seventeen glass filters,

submitted by Hellige, Inc. , has been carried out. From this

study, it has been found that all seventeen glass filters pass

the specifications for the relocated and respaced Union color

scale as given in NBS Research Paper RP2103* It is planned

that these filters will be retained at this Bureau as the

master standards of this color scale.
.

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The author wishes to express his thanks to Miss M»A. Belknap

for making all of the measurements by means of the Beckman Model

DU spectrophotometer, and to Dr. G. Wyszecki, guest worker at

the National Bureau of Standards, Miss G. M. Haas, and Messrs*

K. L. Kelly and W. A. Hall for their assistance in computing and

checking the data.,

-aTable I

Chromaticity Coordinates in the UCS System (r,b), and Luminous

Transmit tances, Y, of the Seventeen Glass Filters Submitted by

Hellige, Inc« Duplicating the Relocated and Re spaced Union

Color Scale for

Designation

of

Filter Max©

Lubricating Oil and Petrolatum*

Chromaticity Coordinates

r b

Min* Max* Min*

Luminous

Max*

Transmittance

I

Min*

B(0.5) Oo h68 0.1*61 0.1*56 0*071 0.066 0.059 0.89 0.88 0.83

C(l.O) .1*95 oi|88 .1*83 .01*2 .035 •030 .80 oil .71*

D(1.5) .527 .518 .515 *021 .016 *009 • 70 •66 o6h

E(2.0) .550 .51*6 • 012 .008 • 000 • 58 .55 *52

F(2.5) .588 .576 .576 .008 .001* -.001* .U6 .1*3 .1*2

G(3.0) .617 .609 .605 *007 *002 -.005 *.33 *32 *29

h(3.5) o6ii6 .639 *63U .007 *002 -.005 .21* 2U • 20

I(1*.0) .677 0668 o665 *007 *001 -.005 .163 .162 .11*1

J(l*.5) *709 *700 .697 *007 *000 -.005 •317 •117 •101

K(5.0) .71*2 *733 *730 .006 • 000 -.006 .087 • 086 .075

l(5.5) .776 .766 .761* .006 • 000 -.006 .063 .060 .053

M(6.0) .8n .801* *799 .006 • 000 -.006 • OU4 .01*2 .036

N(6.5) .81*7 .81*0 .835 .006 • 000 -.006 • 029 • 027 • 023

0(7.0)

C*- co 0 *000 .016

.883 .871 .006 -.006 .018 .Oil*

0(7.0)** .875 • 000 •017

P(7.5) ,921 .911* *909 .006 • 000 -•006 .0089 .0078 •0073

Q(8.0) .962 .956 .950 .006 • 000 -.006 .0028 .0025 • 0022

^Modified filter submitted by Hellige, Inc 0 to reduce overall

thickness

-9-

References

1, D. B. Judd, Lo Plaza, M. A. Belknap, A suggested relocation

and respacing of the Union Colorimeter scale for lubricating

oil and petrolatum, J. Research NBS 559 (1950), RP2103.

2* ASTM Tentative method of tests for color of lubricating oil

and petrolatum by means of ASTM colorimeter, ASTM Designations

D155-45T, ASTM standards, part III-A, p„ £39* (1946)

o

3<» Report of NBS Test No® 5796£, issued December l£, 1929* to

ASTM Committee D-2 on Petroleum Products and Lubricants.

4o J. C. Schleter, Design of sixteen filters for the relocated

and respaced Union Colorimeter scale for lubricating oil and

petrolatum, NBS Report 2012, October 24* 1952.

5o A. C. Hardy, A new recording spectrophotometer, J. Opt. Soc

.

Am. 2£, 305 (1935K

6. J. L. Michaelson, Construction of the General Electric

recording spectrophotometer, J. Opt. Soc. Am. 365 (193$);

also K. S. Gibson, and H. J. Keegan, Calibration and

operation of the General Electric recording spectrophotometer

of the National Bureau of Standards, J. Opt. Soc. Am. 2£, 372

(193£).

7» J. C. Schleter, Design of sixteen filters for the relocated

and respaced Union Colorimeter scale for lubricating oil and

petrolatum, Supplement I to NBS Report 2012, NBS Report 2935*

December 15, 1953®

£«, Proceedings, Eighth Session, Commission Internationale de

L T Eclairage, Cambridge, England, September 1931* p* 19 to

29; also A. C. Hardy, Handbook of Colorimetry, Cambridge,

Technology Press, tl936); also D. B. Judd, The 1931 IoCvI.

standard observer and coordinate system for colorimetry,

J. Opt. Soc. Am. 2J, 359 (1933).

9. D. B. Judd, A Maxwell triangle yielding uniform ehromaticity

scales, J. Research NBS 14, 41 (1935) RP756; also J. Opt.

Soc. Am 0 2j>, 24 (1935).

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Functions and Activities

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