The optical properties of container glass

Journal of Non-Crystalline Solids 47, 1 (1982) 27-46 North-Holland Publishing Company

27

THE OPTICAL PROPERTIES OF CONTAINER GLASS H. N. M i l l s , P.E. Section Head, Glass Technology O w e n s - I l l i n o i s , I n c . , Glass Container D i v i s i o n One Seagate Toledo, Ohio 43666 U.S.A. Those o p t i c a l p r o p e r t i e s of glass of most i n t e r e s t in the s o d a - l i m e - s i l i c a container composition f i e l d are r e f r a c t i v e index, r e f l e c t i o n , transmittance and absorption. These p r o p e r t i e s r e l a t e to measurement of i n t e r n a l stress, l i g h t p r o t e c t i o n , heat transmission and visual c o l o r . Spectrophotometric measurement of transmission/absorbance properties and use of the C.I,E. system to express color parameters are useful in c o l o r control to meet customer s p e c i f i c a t i o n s . INTRODUCTION This paper presents an overview of those o p t i c a l properties of glass of most i n t e r e s t in the s o d a - l i m e - s i l i c a container composition f i e l d . Specifically, these o p t i c a l p r o p e r t i e s are r e f r a c t i o n , r e f l e c t i o n , absorbance and transmission. L u r e 1 gives the d e f i n i t i o n of these terms as they w i l l be subsequently used. FIGURE 1

DEFINITIONOF TERMS 1. REFRACTION• THE BENDINGOF LIGHT TOWARDSTHE NORMAL WHEN ENTERING GLASS FROM AIR DUE TO A DECREASEIN VELOCITY. THIS PHENOMENONIS EXPRESSED BY SMELL'S LAW OF REFRACTION. I

n

=

REFRACTIVEINDEX

V AIR = VELOCITY OF LIGHT IN AIR V AIR M = VGLASS

SINE i SINE r

V GLASS = VELOCITY OF LIGHT IN GLASS i = ANGLE OF INCIDENCE r = ANGLE OF REFRACTION m

2. REFLECTION - THE BACKWARDSCATTEROF INCIDENT LIGHT FROM k SURFACE DEPENDING ON THE ANGLE OF INCIDENCE, THE REFRACTIVE INDEX AND THE SURFACE CONDITION. 0 0 2 2 - 3 0 9 3 / 8 2 / 0 0 0 0 - 0 0 0 0 / $ 0 2 . 7 5 © 1982 North-Holland

28

H.N. Mills / Container Glass

FIGURE i (CONT'D)

DEFINITIONOF TERMS Cont.

3. ABSORBANCE • THE INTERNALDECREASEIN LIGHT ENERGYPASSING THROUGHGLASS DEPENDINGON THICKNESS, COMPOSITION, TEMPERATUREAND THERMALHISTORY. 4. TRANSMISSION • THE RATIO BETWEENTHE INTENSITY OF THE EMERGING BEAM AND THE INCIDENT BEAM OF LIGHT. IO ~_1 = TRANSMISSION T- ~

L~"

INTENSITYOF REAM OUT INTENSITY OF INCIDENT REAM

The relationship of the optical properties is shown in Figure 2 with glass of thickness ( t ) and surrounded by a i r . (I~) is the i n t e n s i t y of the incident beam s t r i k i n g the glass surface at an an~le of incidence equal to angle ( i ) . (IRA) is the loss due to r e f l e c t i o n at the glass surface. (IGI) is the i n t e n s i t y of the -light entering the glass. (This i n t e n s i t y is equal to I i - IRA). Angle (r) is the angle of r e f r a c t i o n . (IG2) is the i n t e n s i t y of l i g h t at the emerging surface following absorbance of a portion of the l i g h t energy by the glass. (IG2) is related to (IGI) by the logarithmic function (e-Bt), where (B) is the absorption c o e f f i c i e n t and ( t ) is the glass thickness. (IRG) is the l i g h t reflected at the emerging surface. The i n t e n s i t y of the beam emerging from the glass is shown by ( I o ) . This i n t e n s i t y is equal to (IG2) minus the r e f l e c t i o n loss at the emerging surface (IRG), The r a t i o of Io, emerging beam i n t e n s i t y , to E l i ) , incident beam i n t e n s i t y , is the transmission of the glass, as previously defined in Figure I .

H.N. Mills' / Container Glass

29

FIGURE 2

GLASSTRANSL11TTANCERELATIONSHIPS

|

SURFACE GLASS SURFACE

I

t:THICKNESS

AiR

1. Zei : Zi.Zra

2. ~ z : ]~ieBt

[B= ABSORBTIONCOEFFICIENT)

3. Io -- ~ 2 -1zg 2.

Refractive Index vs Composition

Figure 3 l i s t s

some of the important facts concerning r e f r a c t i v e index.

H.N. Mills / Container Glass

30

FIGURE 3

REFRACTIVEINDEX 1. DEPENDENTON: o GLASSCOMPOSITION •

WAVELENGTHOF INCIDENT LIGHT

•

THERMALHISTORY OF THE GLASS

•

TEMPERATURE

•

DENSITY

•

INTERNALSTRESS

2. VALUES FOR CONTAINERGLASS: WITH REFERENCETO SODIUM 0 LINE [588.3 nm): N o = 1.490 TO 1.520 3. RELATIVE VELOCITY OF LIGHT IN GLASS COMPAREDTO AIR: No -

V AIR

No = 1.50

V GLASS VAiR VGLASS - - 1.50

- 0.67 VAIR

The r e f r a c t i v e index of glass is dependent upon the glass composition, the wavelength of incident l i g h t , thermal history of the glass, temperature, densit{, and internal stress. The r e f r a c t i v e index generally increases with density and decreasing wavelength. Any measurement of r e f r a c t i v e index requires that the l i g h t source be specified. For comparison of d i f f e r e n t glasses, i t is common practice to use monochromatic l i g h t of the sodium D l i n e (589.3 nm) for measurement of r e f r a c t i v e index. Soda-lime container glass would have an ND in the range of 1.490 to 1.520. Since the index of r e f r a c t i o n has been defined as the r a t i o of the l i g h t v e l o c i t y in a i r to the l i g h t v e l o c i t y in glass, the r e l a t i v e v e l o c i t y of l i g h t in glass can be calculated. For an index of refraction equal to 1.50, the v e l o c i t y of l i g h t in glass is 67% slower than in a i r . The r e f r a c t i v e index of glass, l i k e density, is an a d d i t i v e property. Each oxide contributes to the final value in proportion to the mole f r a c t i o n present in the glass. F i g u r e 4 indicates two forms of l i n e a r equations that have been used for the calculation of r e f r a c t i v e index, The f i r s t equation of Huggins & Sun relates r e f r a c t i v e index to density with a m u l t i p l i e r consisting of the summation of (VM D) constants m u l t i p l i e d by the decimal f r a c t i o n (fm) for each oxide. ( D e t a i l s ' o f this method along with the factors are published in the Journal of the American Ceramic Society, Vol. 26, No. 1 1943.)

H.N. Mills / Container Glass

31

The second l i n e a r equation to c a l c u l a t e r e f r a c t i v e index uses a summation of mole f r a c t i o n m u l t i p l i e d by a constant f o r each oxide. This form of equation was used by C. L. Babcock in his work to r e l a t e c e r t a i n physical properties of glass to the presence of d i f f e r e n t s t r u c t u r a l types in s i l i c a t e glasses. This work was published in the Journal of the American Ceramic Society, Vol. 51, No. 3 1968.

FIGURE q

CALCULATIONOF REFRACTIVEINDEX FROM COI,IPOSITION ii

TYPICAL EQUATIONS: 1. N O : 1 + P =e ru, D fm

[HUGGINS& SUN)

WHERE: No -'- REFRACTIVEiNDEX P = DENSITY r M,o = CONSTANTFOR A GIVEN OXIDE fm : DECIMAL FRACTION OF EACH OXIDE 2. No : A

Si02 + B N a 2 0 +

CCaO + .... (BABCOCKJ

WHERE: A,B,C : CONSTANTSCHARACTERISTICOF EACH DXlDE Si 02, Na 2 O, CaO : MOLE FRACTION OF EACH OXIDE,

3.

Stress Optical C o e f f i c i e n t

Homogenious, well annealed glass is o p t i c a l l y i s o t r o p i c , i . e . has one r e f r a c t i v e index, does not p o l a r i z e l i g h t and shows no b i r e f r i n g e n c e . Under s t r e s s , however, glass behaves as a u n i a x i a l o p t i c a l l y negative c r y s t a l . I t becomes double r e f r a c t i v e with f a s t and slow rays p r o p o r t i o n a l to the i n t e n s i t y of the stress and whether t e n s i l e or compressive. The r e l a t i o n s h i p between double r e f r a c t i o n or b i r e f r i n g e n c e and stress is expressed in terms of the stress o p t i c a l c o e f f i c i e n t . Figure 5 i l l u s t r a t e s t h i s r e l a t i o n ship. The stress o p t i c a l c o e f f i c i e n t constant is the r a t i o of the r e t a r d a t i o n to the product of the stress and glass thickness. For soda-lime container glass, the stress o p t i c a l c o e f f i c i e n t is 2.59nm-cm/kg. The r e t a r d a t i o n is the distance in nanometers that the slow ray lags behind the f a s t ray in emerging from the sample.

H.N. Mills / Container Glass

32

FIGURE 5

STRESS OPTICALCOEFFICIENT B: ~

r

WHERE:

m

B = STRESS OPTICAL COEFFICIENT r = RETARDATION[nm} S = STRESS [Kg/cm2 } t = THICKNESS OF GLASS [cm] n

["B" FOR SODA-LIME CONTAINERGLASS • 2.59

3.1

nm-cm

-/i-- }

Measurement of Retardation

A most important use of the s t r e s s - o p t i c a l properties of container glass is in the evaluation of non-homogenious glass and the stresses set up due to differences in thermal expansion. An inhomogeneity or cord that is in tension has a slow ray which v i b r a t e s p a r a l l e l to the cord length and a fast ray which v i b r a t e s perpendicular to the cord length. The converse is true f o r a cord in compression. The measurement of r e t a r d a t i o n f o r container glass is normally accomplished using a b o t t l e cross-section sample or " r i n g section". The ring section is immersed in a f l u i d having the same r e f r a c t i v e index as the glass, (nominally 1.50), and placed on the stage of a p o l a r i z i n g microscope with t i n t plate i n s e r t e d The f u l l wave t i n t plate gives a background r e t a r d a t i o n of 565nm (magenta color) and enables the observer to note the interference colors due to the stress in the cord. When the ring section sample is oriented so that a weak tension cord's length (slow ray) is aligned perpendicular to the slow ray of the f u l l wave t i n t p l a t e , the cord w i l l appear orange under crossed polarized viewing. This is the r e s u l t of the s u b t r a c t i v e e f f e c t of the perpendicular slow rays. Figure 6-A is a photomicrograph of a ring section oriented in the orange p o s i t i o n . The band of yellow-orange c o l o r is a cordy section in tension. The blue bands are in compression.

H.,V. Mills / Container Glass

FIGURE 6-A When retardation is to be measured, a calibrated quartz wedge is normally used in place of the microscope ocular at a 450 angle to the crossed polarized l i g h t path. With the t i n t plate removed, in the orange p o s i t i o n , the quartz wedge is adjusted so that the black line at the "0" c a l i b r a t i o n is in the center of the viewing f i e l d . Tension stress w i l l displace the black l i n e to the l e f t and compressive stress to the r i g h t . Figure 6-B shows the same ring section photographed with the quartz wedge in place. The scale of retardation in wavelengths or nanometers on the quartz wedge is not readable in the photo o f ~ . In practice, the retardation can be read from this scale by the displacement of the black line. 3.2

Calculation of Stress

The stress optical c o e f f i c i e n t formula of Figure 5 is used for the calculation of the stress in the cord now that the retardation has been measured with the quartz wedge.

FIGURE 6-B

33

tt.~%~ Mills / Container Glass

34

4.

Reflection

The loss of i n c i d e n t l i g h t energy by r e f l e c t i o n from the glass surface is an important p r o p e r t y , useful in the measurement of surface coating u n i f o r m i t y and in the measurement of the l i g h t transmission c h a r a c t e r i s t i c s of various c o l o r of glasses. For normal or perpendicular incidence of l i g h t on a glass surface, the f r a c t i o n r e f l e c t e d by a single surface can be c a l c u l a t e d from Fresnel's formula as shown in Figure 7. For soda-lime glass, with a nominal r e f r a c t i v e index of 1.50, the l i g h t r e f l e c t e d from each surface is 4%. For spectrophotometric c o l o r measurements on glass in a i r , reflectance losses of 8% (4% from each surface) must be taken into consideration when measuring transmittance.

FIGURE 7

REFLECTION [NORMAL INCIDENCE] ":

(,tl'

w,E :

R = FRACTION REFLECTED n = REFRACTIVE INDEX FOR SODA-LIME GLASS OF I n :

\1.5o+V

1.50] •

= Io.o21'

, : 0.04 OR 4.0%

5.

Transmittance/Absorption

The o p t i c a l p r o p e r t i e s of transmission and absorbance have already been defined in Figure I. The amount of i n c i d e n t l i g h t energy transmitted is a function of r e f l e c t i o n losses and the i n t e r n a l absorbance of the glass. The s e l e c t i v e absorbance of glass of various wavelengths in the v i s i b l e spectrum r e s u l t s in c o l o r sensation to an i n t e g r a t i n g instrument such as the human eye. This s e l e c t i v e absorbance is due to the presence of c o l o r i n g oxides in the glass such as oxides of iron and/or chrome.

lt, N. Mills / Container Glc~s's

35

5.1 Measurement The measurement of transmittance/absorbance of a glass at various wavelengths is accomplished by means of the spectrophotometer. Figure 8 is a schematic view of the o p t i c s of such an instrument, which is capable of r e s o l v i n g white l i g h t from a tungsten lamp i n t o monochromatic l i g h t by means of a prism.

FIGURE 8

SPECTROPHOTO51ETEROPTICSYSTEM j,

-,i

,,,

"

CONDENSINGMIRI~O.__..~R

I

[

j

FERYPRISMA----~-~._ .,.~1

\~7""

P~NEMIR~R

~

-

-

-

I TmGS~L~P

I

..

~j

L

Z

I ~oMpSpAB~LEEHTI

ENTP, ANC~

I -~

~ -

I

_"---~

LEN~ SAMF~CELL1

The transmission is measured in a i r at each desired wavelength and corrected to a standard thickness using the equation shown in Figure 9. (This equation can be expressed in homograph form or constructed as a c i r c u l a r s l i d e rule to f a c i l i t a t e the thickness c o r r e c t i o n c a l c u l a t i o n . ) Standard thickness used for glass container colors are: 2 or lOmm f o r green glasses, 2 or 3.175mm f o r amber glass, and 38mm f o r f l i n t glass. For visual c o l o r determinations, the transmission is measured between 400 and 70Ohm wavelength. U l t r a - v i o l e t c h a r a c t e r i s t i c s are measured between 300-40Ohm and i n f r a - r e d between 700-120Ohm.

tI.N. Mills / Container Glass

36

FIGURE 9

THICKNESS- TRANSMITTANCEEQUATION T2 LOG 0 . 9 2 -

t2 Tw t l LOG 0.92

WHERE: t l = SAMPLE THICKNESS t2 = STANDARDTHICKNESS T! = MEASUREDTRANSMISSION(DECIMAL) T2 = CORRECTEDTRANSMISSION(DECIMAL)

5.2

C.I.E. System

The C.I.E. system of color measurement and notation has received almost universal acceptance f o r the evaluation of glass c o l o r , i n c l u d i n g f l i n t or white glass. "The Handbook of Colorimetry" by Arthur C. Hardy presents an e x c e l l e n t explanation of the system. The C.I.E. system uses a c h r o m a t i c i t y diagram as the locus of a l l the colors of the visual spectrum from v i o l e t to red or from 400 to 700nm. Figure I0 shows the c h r o m a t i c i t y diagram. The neutral or c o l o r l e s s p o i n t , from which the s t r a i g h t wavelength lines r a d i a t e , is the l o c a t i o n of the l i g h t source being u s e d - - l l l u m i n a t e "C" or average d a y l i g h t f o r glass transmission work. The r e l a t i v e s a t u r a t i o n or P u r i t y of a given color is the distance from the neutral point to the outer perimeter and shown by the concentric curves around the neutral p o i n t . The c h r o m a t i c i t y diagram is u t i l i z e d by c a l c u l a t i n g the t r i c h r o m a t i c c o e f f i c i e n t s from the transmission data and using the (x) and (y) values to locate the c o l o r on the diagram.

X

¢J1

o

oo o

¢~ ¢-j

o

r~

c.D ¢~

o o

Y

fJI

cn

o

¢J!

¢.n

~D ~o

~o

mm

m

C-J

mmm

~o ¢~

¢~

FN

~

C

H.N. Mills / Container Glass

38

A glass c o l o r can then be characterized by three factors from the C.I.E. system at a specified thickness as shown in Figure I I . The Dominant Wavelength and % Purity are determined from the c h r o m a t i c i t y diagram and the % Brightness is c a l c u l a t e d from the summation of the (y) transmission data. % Brightless is a measure of the transmitted l i g h t p e r c e p t i b l e by the human eye.

FIGURE 11

COLORCHARACTERISTICS.C.I.E. SYSTEM 1. DOMINANTWAVELENGTH[nm) 2. % PURITY 3. % BRIGHTNESS

6.

F l i n t Glass Transmission

The glassmaking oxides s i l i c a , soda, lime and alumina do not absorb v i s i b l e l i g h t . The transmission curve of f l i n t glass has a very high transmittance in the v i s i b l e range i f pure raw materials are used. In p r a c t i c e , however, the presence of Fe203 up to 0.07% and Cr203 up to 0.0005% are not unusual in container f l i n t due to impure raw materials and contamination. The c o l o r i n g e f f e c t s of these oxides must be masked by the a d d i t i o n of complimentary c o l o r s , normally from selenium and cobalt oxide. 6.1

Effect of Iron Oxide

Figure 12 shows a transmission curve of a f l i n t glass containing 0.068% t o t a l iron expressed as Fe203. Absorptions below 500nm are due to iron in the f e r r i c state. Above 500nm, the absorption s t e a d i l y increases (decreasing transmission) due to the absorbing power of ferrous iron. Ferric iron or Fe203 has i t s maximum absorption in the v i s i b l e region at 440nm, and ferrous iron or FeO at about 105Ohm in the i n f r a - r e d . The f e r r i c iron color is yellow-green while the ferrous iron color is blue-green. The ferrous iron has about I0 times the c o l o r i n g power of f e r r i c iron and i s , t h e r e f o r e , the dominant f a c t o r in f l i n t color control. Usually about o n e - t h i r d of the t o t a l iron e x i s t s as FeO in f l i n t glass.

H.N. Mills / Container Glass

39

FIGURE 12

FLINT GLASS - NO DECOLORIZERS 100 90

TOTAL IRON AS FE203 = .068% (SAMPLE THICKNESS = 38 ram)

80

i '° 60

50

40 30 20 400

I 500

I 600 WAVELENGTH [nmJ

t 700

6.2 D e c o l o r i z a t i o n The d e c o l o r i z a t i o n of f l i n t glass may i n v o l v e the o x i d a t i o n o f some o f the f e r r o u s i r o n to f e r r i c and the a d d i t i o n o f complimentary c o l o r a n t s to mask the remaining green c o l o r a t i o n . The complimentary c o l o r o f any green i s some shade o f p u r p l e . A s t a b l e purple c o l o r f o r d e c o l o r i z i n g f l i n t glass i s obt ai ned from the pink o f elemental selenium and the blue from c o b a l t o x i d e . Figure 13 shows the t r a n s mission curve o f the f l i n t glass c o n t a i n i n g .068% t o t a l i r o n as Fe203 t h a t has been d e c o l o r i z e d using a combination o f o x i d a t i o n and a d d i t i o n o f selenium and c o b a l t oxide as d e c o l o r i z e r s . (The same glass w i t h o u t d e c o l o r i z e r s from Figure 12 is shown w i t h a dashed l i n e . ) The net e f f e c t o f the a d d i t i o n s has been to s t r a i g h t e n out the transmission curve at a lower average t r a n s m i s s i o n , or % Brightness in C.I.E. terms. The undecolorized f l i n t has a % Brightness o f 76.5 w h i l e the d e c o l o r i z e d glass has a % Brightness o f 64.7%. A d d i t i o n o f any c o l o r a n t s to a glass decreases the % Brightness.

-

50 400

60

80 _

90

100 -

500

~ .-.--...

WAVELENGTH

600

---

'~

\

700

DECOLORIZED + OXIDATION

NO DECOLOREIZERS

(SAMPLE THICKNESS - 38 mm)

DECOLORIZED FLINT GLASS CONTAINING .068% TOTAL Fe 2 0 3

FIGURE 13

tI,.,V. MilZs / Container Glass

41

Figure 14 locates the undecolorized and decolorized f l i n t glasses on the C.I.E. c h r o m a t i c i t y diagram. Oxidation alone increases the dominant wavelength from p o i n t "A" to point "B". Addition of selenium and cobalt oxide r e s u l t s in movement to point "F", f o l l o w i n g the r e s u l t a n t of the selenium/cobalt a d d i t i o n c h r o m a t i c i t y l i n e s . The e f f e c t of d e c o l o r i z a t i o n has been to increase Dominant Wavelength from 495nm to 520nm and decrease P u r i t y from 4.0% to 0.1%. F l i n t glasses with P u r i t y less than 2% are considered well decolorized.

FIGURE 14

L~-

,oo L\ x t , , .280

~/~ .300

/ .320

VALUES OF X

x

/ .340

H.N. Mills / (~mtainer Glass

42

7.

Colored Glasses

The a d d i t i o n o f c e r t a i n m e t a l l i c oxides to a base soda-lime glass can impart v i s u a l c o l o r due to s e l e c t i v e a b s o r p t i o n at c h a r a c t e r i s t i c wavelengths in the v i s u a l spectrum. The e f f e c t o f i r o n in f e r r i c and f e r r o u s s t a t e s has a l r e a d y been discussed under the subject o f f l i n t glass t r a n s m i s s i o n . 7.1

C o l o r i n 9 Oxides

Figure 15 l i s t s a number o f the c o l o r a n t s of commercial importance f o r c o n t a i n e r glass. The valence s t a t e o f the m e t a l l i c ion is c r i t i c a l to achieving the desired c o l o r or to make use o f i t s absorbing c h a r a c t e r i s t i c at p a r t i c u l a r wavel e n g t h s , such as the u l t r a - v i o l e t r e g i o n . An example o f t h i s is chromium o x i d e , which may e x i s t as Cr +2 or Cr +6.

FIGURE 15

COLORANTS MATERIAL

FORMULA

COLOR

1. IRONOXIDE

Fe203, FeO

YELLOWGREEN,BLUE GREEN

2. IRONCHROMITE

FeO-Cr203

GREEN

3. COBALTOXIDE 4. POTASSIUMDICHROMATE

Co304 K 2 Cr2 0 ?

BLUE YELLOW-GREEN

5. SELENIUM

Se°

PiNK

6. COPPEROXIDE

CuO

BLUE

7. MANGANESEOXIDE

Mn2 0 3

PURPLE

II. NICKELOXIDE

NiO

BROWN

9. IRON PYRITE

FeS

AMBER

10. COPPER

Cu°

RED

11. TITANIUMOXIDE

TiO 2

YELLOW (WEAK)

, Ce 02

YELLOW (WEAK)

12. CERIUMOXIDE

tt.N. Mills / Container Glass

43

Figure 16 shows the transmission curves f o r an emerald green glass with a l l the c h r o m i ~ a s Cr +2 and one with a p o r t i o n of the chromium as Cr +6. The major d i f f e r e n c e is the u l t r a v i o l e t absorption o f the Cr +6 glass which can be a useful property in p r o t e c t i n g the container contents from the sun's U.V. rays.

EIO0[

FIGURE 16 EMERALD GREEN NORMAL VS U.V. ABSORBING

@ ?5 Nkl U

U.V.

Z

N

~

50

z

Z U IX

500

40O

600

700

WAVELENGTH IN NANOMETERS

7.2

Spectral Transmittance Curves

Figure 17 shows the spectral transmittance curves f o r a number of colored glasses based on 2mm thickness. The reduced amber glass and the copper ruby glass o f f e r the best l i g h t p r o t e c t i o n f o r the contents o f containers made with these colors.

so

0

-~ 2:

z

E E

40o

400

100

o

_~ 2:

z

:~ 50

E

z <[

@ 75

E

100 E

I 600

I 600

WAVELENGTH IN NANOMETERS

I 500

WAVELENGTH IN NANOMETERS Mn20 a

I 500

COBALT

|

I ?uO

?uO

lOO

400

FIGURE 17

lOO

0

25

ix

Z

0

~- 25

i-

Z

z

@ 75

z <

500

400

600

f

I 600 WAVELENGTH IN NANOMETERS

I 500

Cu O

WAVELENGTH IN NANOMETERS

AMBER

| 700

9uO

100

25

400

.~ so

Z

@ 75

400

25

so

100 E E ¢N

Z

~-

Z

Z

@ 75

E E

500

Cu RUBY

600

I 600 WAVELENGTH IN NANOMETERS

I 500

Ni O

WAVELENGTH IN NANOMETERS

SPECTRAL TRANSMITTANCE CURVES

~ i '°

@ 75

E E

COLORED GLASSES-

I 700

?00

ILN. Mills / Container Glass

7.3

45

§~ecifications

The four container glass colors of greatest commercial importance are f l i n t , amber, Georgia Green, and emerald green. Typical specifications for these colors in the United States of America are shown in Figure 18. These specifications are developed between the glass producers and the customers to provide uniformity among suppliers and to meet desired l i g h t protective standards. The C.I.E. system is used as the basis in most cases.

FIGURE 18

GLASSCOLORSPECIFICATIONS-TYPICAL COLOR

THICKNE$$Into)

DOM. WAVELENGTHinto) % PURITY % BRIGHTNESS < 3

OTNER

1. FLINT

38

< 573

> 68

2. GA. GREEN

10

515-545

2-5

70-80

T-885, T-800, T-945 AV.> 49%

3. EM. GREEN

10

554-558

58-74

30-40

T-800 > 27%

4. AMBER

3.175 IT-550 BETWEEN 3.175 TYPICAL 584

15-22%) 95

20

T-850 ~.< T-550

LIMIT

46

t£N. Mills / Container Glass

REFERENCES I.

E. B. Shand, "Glass Engineering Handbook", McGraw-Hill, 1958

2.

F. V. Tooley, "Handbook of Glass M a n u f a c t u r e " - V o l . l l , Ogden Publishing 1960

3.

G. W. Morey, "The Properties of Glass", Reinhold Publishing, 1954

4.

C. J. P h i l l i p s , "Glass-lts I n d u s t r i a l Applications", Reinhold Publishing 1960

5.

A. C. Hardy, "Handbook of Colorimetry", Technology Press, Cambridge, 1936

6.

W. A. Weyl, "Coloured Glasses", Society of Glass Technology, S h e f f i e l d , 1951

7.

M. L. Huggins & K. H. Sun, "Calculation of Density and Optical Constants of a Glass from Its Composition in Weight Percentage", Journal of The American Ceramic Society, Vol. 26, No. I , 1943

8.

C. L. Babcock, "Substructures in S i l i c a t e Glasses", Journal of The American Ceramic Society, VoI. 51, No. 3, 1968

9.

J. Jasinski, " F l i n t Glass Decolorizing and Color Control", Owens-lllinois GCD D i v i s i o n , 1968

I0.

J. Jasinski, "Cord Analysis and Evaluation in Glass Containers", Owensl l l i n o i s GCD, Technical Center, 1974