Glass manufacture

GLASS
IN
PACKAGING
C.S.Purushothaman

CSP TRG AIDS - AUG 2008 1

SCOPE
BASICS
MANUFACTURE
DESIGN FEATURES
TYPES & PROPERTIES
PERFORMANCE & TESTING


What is Glass?

SUPERCOOLED LIQUID
LIQUID WHICH IS COOLED TO A STAGE
WHERE ITS VISCOSITY IS SO GREAT
THAT THE MOLECULES DO NOT MOVE
FREELY ENOUGH TO FORM CRYSTALS


What is glass made of?

Sand – 70%
Soda Ash – 15%
Limestone – 10%


Three of most common rock forming minerals on
earth. Chemically named: quartz sand / rock
crystal
Properties: Extremely heat durable
Chemical stack resistance

Naturally:
Mechanical & chemical weathering of quartz-bearing
igneous & metamorphic rocks
Chemically weathering:
Less stable minerals
• break down to become silica sand

Anhydrous sodium carbonate
Texture: soft
Color: grayish & white
Appearance: lump / powder in nature

Naturally:
Erosion of igneous rock form sodium deposits
Transport by waters as runoffs & collect in basins
When sodium comes in contact with CO2, precipitates
out sodium carbonate

Includes hydrated lime Ca (OH)2 & quicklime CaO
Only quicklime can use to make glass

Cullet – Recycled glass
(from plant and post
consumer) used at levels
as high as 80% when
available. It is needed
and added to enhance
the melting rate and it
significantly reduces
energy required for glass
production.


Glass Container Recycling
 100% recyclable
– Can be recycled again and again
with no loss in quality or purity
– In 2005, 25.3% of glass container
recycled
 Good for the environment
– recycling glass reduces
consumption of raw materials,
extends the life of plant
equipment, and saves energy
 Lighter weight
– More than 40% lighter than 20
years ago.


Benefits of Using Quality Cullet
 Over a ton of natural resources are saved for
every ton of glass recycled.
 Energy costs drop about 2-3% for every 10%
cullet used in the manufacturing process.
 For every six tons of recycled container glass
used, one ton of carbon dioxide, a greenhouse
gas, is reduced.
 Glass has an unlimited life, it can be recycled
over and over again.
Lesser sodium oxide stronger the glass
Aluminium oxide increases the hardness & durability.
Use of Na2SO4 & Arsenic reduces blisters


METALS USED TO IMPART COLOR TO GLASS
Cadmium Sulfide Yellow
Gold Chloride Red
Cobalt Oxide Blue-Violet
Manganese Dioxide Purple
Nickel Oxide Violet
Sulfur Yellow-Amber
Chromic Oxide Emerald Green
Uranium Oxide Fluorescent Yellow, Green
Iron Oxide Greens and Browns
Selenium Oxide Reds
Carbon Oxides Amber Brown
Antimony Oxides White
Copper Compounds Blue, Green, Red
Tin Compounds White
Lead Compounds Yellow
Manganese Dioxide A "decoloring" agent
Sodium Nitrate A "decoloring" agent

Three standard furnace colours are Flint, Amber and Emerald
Blue coloured bottle make product look white
OPAL: MINUTE CRYSTALS OF FLUORINE COMPOUNDS ARE ADDED (CALCIUM FLUORIDE)


CULLET SAND OTHER RM

SORTING
WASHING & SIEVING

CRUSHED TO
15 – 20 mm dia
WEIGHED

MIXER

FURNACE
1500 deg C

FOREHEARTH

GOBS CUT OFF

MOULDING

COOLING

ANNEALING LEHR

PROTECTIVE COATINGS

BOTTLES & JARS

SCHEMATIC DIAGRAM OF GLASS MANUFACTURING

Cullet + SAND + OTHER RM MELTED in furnace (1500 0 C) (100 to
500 MT)

Colour agents added in melt or forehearth
Glass has no distinct melting or solidifying temperature
Decolorizers are added to remove the colour by mineral impurities


GOB FORMATION
Gob is one individual mass of molten
Gobs ---to form blank mold glass which makes one container
Molten glass flows depending on the
bottle size.
Mechanical shears snip off "gobs" of
molten glass. Each makes one
container.
Falling gob is caught by spout and
directed to blank molds.
Mass-production is made up of several
individual sections, each is an
independent unit holding a set of bottle-
Furnace draw-off orifice and gob making molds.
shears Large bottles consists of a blank mold
and a blow mold.
Orifice 12 mm to 50mm
Higher production using double or triple
gobs on one machine. two or three
blank molds and similar blow molds.

GLASS MOULDING
BLOWING (Bottle or Jar)
TWO STAGE MOULDING
BLANK MOULD
– blank mold forms neck and initial shape
– parison mould where gob falls and neck is formed
– has number of sections
– finish section
– cavity section (made in two halves to allow parison removal)
– a guide or funnel for inserting gob
– a seal for gob opening once gob is settled in mold
– blowing tubes through the gob and neck openings

BLOW MOULD - blow mold produce the final shape

TWO TYPES OF PROCESSES


GLASS MOULDING
TWO TYPES OF PROCESSES
BLOW & BLOW PRESS & BLOW


BLOW & BLOW

Blow-and-blow process--- for narrow-necked bottles
The two processes differ according to the parison producing.
Blow-and-blow process:
1. Gob dropped into the blank mold through a funnel-shaped guide

(985°C)
2. parison bottomer replaced guide ;air blown into settle mold to
force the finish section. At this point the bottle finish is complete.
3. Solid bottom plate replaced parison bottomer ; air is forced to
expand the glass upward and form the parison.
4. Parison removed from the blank mold, rotated to a right-side-up
orientation for placement into the blow mold.
5. Air forces the glass to conform to the shape of the blow mold.
The bottle is cooled to stand without becoming distorted and is then
placed on conveyors to the annealing oven.


BLOW & BLOW


PRESS & BLOW
press-and-blow process--- for wide-mouthed jars

Gob delivery and settle-blow steps are
similar to blow-and-blow forming.
Parison is pressed into shape with a
metal plunger rather than blown into
shape
The final blowing step is identical to the
blow-and-blow process.
Used for smaller necked containers.
Better control of glass distribution

Press and blow forms
the parison by mechanical action


Bottle Manufacture

Difference of the two processes
Blow-and-blow used for narrow-necked bottles.
Press-and-blow used to make wide-mouthed jars and for increasingly smaller
necked containers. Better control of glass distribution.

Typical production rates range from 60 to 300 bottles per minute, depending
on the number of sections in a machine, the number of gobs being
extruded, and the size of the container.

The blown bottle is removed from the blow mold with takeout tongs and
placed on a deadplate to air cool for a few moments before transfer to a
conveyor that transports it to the annealing oven.


DIFFERENCE IN PROCESSES

Difference of the two processes
Blow-and-blow used for narrow-necked bottles.
Press-and-blow used to make wide-mouthed jars and for increasingly smaller
necked containers. Better control of glass distribution.

Typical production rates range from 60 to 300 bottles per minute, depending
on the number of sections in a machine, the number of gobs being
extruded, and the size of the container.

The blown bottle is removed from the blow mold with takeout tongs and
placed on a deadplate to air cool for a few moments before transfer to a
conveyor that transports it to the annealing oven.


ANNEALING
ANNEALING
to reduce internal stresses; in annealing oven
- Walls are comparatively thick and cooling will not be even.
- The inner and outer skins of a glass become rigid
- The still-contracting inner portion build up internal stresses
- Uneven cooling develop substantial stresses in the glass.
- Bottle passes through an lehr after removal from the blow mold.
- LEHR is a belt passing through the controlled temperature oven at a rate
of about 200mm to 300mm per minute. Glass temp is raised to 5650 C and then
gradually cooled to room temperature with all internal stresses reduced to safe
levels in about an hour as they exit

Improperly annealed bottles are fragile and high breakage
Hot-filling also produce unacceptable breakage levels.


SURFACE COATINGS
SURFACE COATINGS
Purpose--- to reduce the coefficient of friction
Reasons---The inner and outer surfaces have different characteristics
The outer surface comes in contact with the mold and takes
the grain of the mold surface
Both surfaces are PRISTINE, MONOLITHIC, STERILE,
CHEMICALLY INERT.
Pristine glass has high COF, surface scratchinhg and brusing can
occur when surface rub. Surface scratching has lower breakage
resistance
Methods--- hot-end coating ; cold-end coatings
The hot-end coating applied at the entrance to the annealing lehr
to strength the glass surface
Cold-end coatings depending on the filling process and end use.
Typical cold-end coatings---oleic acid, monostearates, waxes,
silicones, polyethylenes
The label adhesive as one cold-end coating.


INSPECTION & PACKAGING

INSPECTION AND PACKING
Use mechanical and electronic means.
1) Squeeze testers subject the container walls to a compressive force
( between two rollers)
2) Plug gauges check height, perpendicularity, inside and outside finish
diameters.
3) Optical devices inspect for stones, blisters, checks, bird swings, and other
blemishes and irregularities by rotating the container past a bank of
photocells (Figure 6.4).
Faulty containers crushing into cullet.
Transported in reusable corrugated shippers;
Shipped on pallets
Automatic equipment used to clear tiers off the pallet and feed into the filling
machine.


DECORATION

Frosting –
Etching by Hydrofluric Acid (HF) / sand blasting – expensive

Printing
Screen Printing – inks are fired. – APPLIED CERAMIC LABEL

Ceramic Frosting
spray with ceramic paint ( ground glass + oil mixture) – fire –
oil evaporates and ground glass fuses on surface.

BOTTLE PARTS

Finish is that part which receives the
closure

Smooth round shapes---easily formed
Suitable on filling lines
Labeled at relatively high speeds
Accurately positioned in spot-labeler
Greater strength-to-weight ratios
Better material utilization


BOTTLE DEFECTS

Flat shapes inherent problems.

“bird swing” and “spike” defects.

Spikes --- glass projections inside
the bottle

Bird swing--- glass thread joining the
two walls

Careful design to avoid stress
points. shapes---difficult to form
angular


FINISH & CLOSURES

FINISH AND CLOSURES
Finishes are broadly classified according to diameter ,sealing method, and
special features.
Continuous-thread (CT), lug, crown, threaded-crown, and roll-
on are common finish designs.
Closures are based on the cost, utility, and decoration
thread profile has a curved or partially semicircular profile
COLOURING
Flint – Clear & Transpareent
Green – Chrome oxide for emerald green upto 5%
Brown – Iron and sulphur for amber
Blue – Cobalt oxide for Blue
Opal – Opaque white


NECK & SHOULDER AREAS

Neck and Shoulder Areas
The impact on filling, air displacement, and dispensing.
Fill level in long narrow necks
Headspace for thermal expansion and facilitate filling.
Manufacturing defect ---choke neck
Ridge on the sealing surface---overpress

Upper shoulder --- below the neck.

Shoulder and neck blending ---important design and production.
lower shoulder--- the integration point between the upper shoulder
and the body.
Contact area


SIDES

Sides
The most generalized areas of the bottle.

Labeling styles and preventing scuffing must be considered. Bottles
designed with label panels to prevent scuffing.
The panel may have prominent base and shoulder ridges.

In angular bottles, rounded corners are preferable for wraparound or
three-side labeling.
Spot labeling is normally a one- or two-sided application.
Labeling of non-round shapes is slower than for round shapes.


HEEL & BASE

Heel and Base
High-abuse area--- start high from the base curving into the base to a
suitable base diameter.
Body-to-base curve should combine 3 radii.
The largest blends body to heel, the smallest blends heel to base.
Diameter as large as possible as a good design.
Center of the base ensure a flat, stable bottom .
Stippled or knurled on the circular bearing surface to protect the scratches
not to weaken the body during handling and usage.
Ketchup bottles and other sauce bottles require:
heel and base be heavier and contoured when expelling the contents.
Wide-mouthed jar bases have designed-in stacking features.
·Container base fits into recessed cap.
· Indented container base fits over cap.
Heel tap --- excess glass distributed to the heel.


STABILITY & MACHINABILITY

Stability and Machinability
bottle's stability
the center of gravity ; the base surface area
problem in manufacturing ---tall and narrow bottles
handling and labeling in packaging line --- high center
Short round oval bodies --- efficient for machine handling and
labeling problems.
baby food ; cold cream jars.
As much as possible, bottles should be designed to be all-around
trouble free to manufacture, fill, close, and ship. Some designs are
inherently weaker or more prone to cause trouble in their filling and
the distribution cycle than others.


VIALS & AMPOULES

Vials and ampoules
Vials and ampoules--- mainly for pharmaceuticals and sera
Preformed tubing stock
Sealed glass containers
Constriction--- easy fracture stress concentration
coated with a ceramic paint
Standard sizes ---1, 2, 5, 10, and 20 ml.
Serum vials
a rubber septum ; an aluminum neck ring.
a needle cannula to withdraw serum
can be accessed several times.
standard sizes--- 1, 2, 3, 5, 10, and 20 ml.
Tumblers --- wide-mouthed containers
Carboys ---bulk containment for acids or chemicals.


BONATED BEVERAGES

Carbonated Beverages
The pressure
factors: gas dissolved in the product. Beverage producers express
this as the number of volumes of gas dissolved in a unit volume of
the product. For example, if a 48 oz. volume of carbon dioxide at
standard conditions is dissolved in 12 oz. of beverage, then the
beverage is said to yield 4 gas volumes.
Carbonated beverage and beer bottles
internal gas pressure : soft drink 0.34 millipascal (50 psi),
beer 0.83 millipascal (120 psi).
capped well
The loss of bottle strength
Bottle designs ---round in cross section
gently curving radii to maximize strength.


Benefits of Glass Packaging
 Inert
 Regal
 Ensures freshness and taste
 Nontoxic
 FDA-approved
 2.5 g/cc


Glass Types and General Properties

inorganic substance fused at high temperatures and
cooled quickly
principle component ---silica (quartz),
Ingredients of components makes different formulations.
Mineral compounds used to achieve improved
properties: decolorizeration, Clarity, Colouring…
Other glass types used for special packaging purposes.
lead compounds, boron compounds, borosilicate
glasses…


Glass Types and General Properties

Advantages as a packaging material:
inert
perfect food container.
impermeability
clarity
regal image
rigidity
stable at high temperatures
Disadvantages :
fragility
high weight
high energy costs


TYPES OF GLASS
Although INERT Sodium and other ions can leach out on
ceratin solution.

USP Type-I Borosilicate Flint (clear), Amber (brown) glass
vials,

USP Type-II De Alkalized Soda Lime Glass(type3) that has
been treated in the lehr with sulphur to reduce alkali
solubility. The treatment produces a disccoloured
appearance.

USP Type-III conventional soda glass


USP TYPE I BOROSILICATE (neutral) GLASS

TYPE 1
ADDITION OF 6% BORON REDUCES LEACHING ACTION
Least reactive glass available for containers.
It can be used for all applications and is most commonly
used to packaged water for injection, UN-buffered products,
chemicals, sensitive lab samples, and samples requiring
sterilization. All lab glass apparatus is generally Type I
borosilicate glass. Type I glass is used to package products
which are alkaline or will become alkaline prior to their
expiration date


USP TYPE II DE ALKALIZED SODA LIME GLASS

Has higher levels of sodium hydroxide and

It is less resistant to leaching than Type I but

GOOD ALKALI RESISTANCE
It can be used for products that remain below


USP TYPE III SODA LIME GLASS

Acceptable in packaging some dry powders which are
subsequently dissolved to make solutions or buffers.
It is also suitable for packaging liquid formulations that
prove to be insensitive to alkali.
Type III glass should not be used for products that are to
be autoclaved, but can be used in dry heat sterilization


USP TYPE NP SODA LIME GLASS

Is a general purpose glass and is used for non-
parenteral applications where chemical durability
and heat shock are not factors.
These containers are frequently used for capsules,
tablets and topical products.


PERFORMANCE
& TESTING
It is important that containers comply with
specification and general industry guidelines
in order to withstand the normal stresses and
mechanical abuse right through until the end
user has finished using it.


VERTICAL LOAD
Forces of this nature might be produced
during capping or through
stacking products on top of each other. To
help ensure glass containers
have adequate vertical load strength, we
test to BS EN ISO 8113-2004
using a Universal Testing Machine.


IMPACT TESTING
To help ensure glass containers have an
adequate impact resistance,
we can test to standard manufacturing
codes of practice using an
industry standard Pendulum Impact
Tester.


THERMAL SHOCK
Hot-fill or heat-treated glassware can be tested for thermal shock
resistance to ensure the
product is fit for the intended purpose. Testing can be carried out to
ASTM C149 and BS EN ISO 7459 either as pass/fail test typically at
42OC downshock or progressive testing to complete sample failure.

EFFECT OF SUDDEN TEMPERATURE CHANGE
EFFECT IS MINIMAL IF BOTH SIDES ARE HEATED OR COOLED
SIMULTANEOUSLY
EFFECTI IS PROMINENT WHEN ONE SURFACE IS HOT AND THE OTHER
SURFACE IS CHILLED


COATING PERFORMANCE
Assessment of surface protection can be
carried out by use of slip
tables and hot end coating technology.
The longevity of the
coating performance can be assessed
using line simulator, whereby bottle to
bottle abrasion damage which may
be expected to occur on a filling line can be
replicated and the
subsequent damage of the container
tested. This is of particular
use for returnable glassware.


INTERNAL PRESSURE RESISTANCE
Carbonated beverage bottles need to be
able to withstand without failure the
pressure produced by their contents over
long periods.


RESIDUAL STRAIN
Measurement of annealing
stresses/residual strain to ASTM C148;


ON-LINE INSPECTION OF GLASS BOTTLES

1.Bottle Spacer. This machine is pre-set to create a space
between the bottles on the conveyer to avoid bottle to bottle
contract.

2.Squeeze Tester. Each bottle is passed between discs that exert
a force to the body of the container. Any obvious weakness or
crack in the bottle will cause it to fail completely with the resulting
cullet being collected by a return conveyor running underneath.

3.Bore Gauger. The internal and external diameter at the neck
finish entrance to the bottle and the bottle height are measured.
Bottles outside specification are automatically rejected by means
of a pusher positioned downstream from the gauger.


4.Check Detector. Focuses a beam of light onto areas of the
container where defects are known to occur from previous visual
examinations, any crack will reflect the light to a detector, which
will trigger a mechanism to reject the bottle.

5.Wall Thickness Detector. This test uses dielectric properties of
the glass, the wall thickness can be determined by means of a
sensitive head which traverses the body section of the container.
A trace of the wall thickness is then obtained and bottles falling
below a specified minimum will be automatically rejected.

6.Hydraulic Pressure Tester. A test carried out on bottles which
will be filled with carbonated beverages and gauges the internal
pressure of every bottle before it is packed.


7.Visual Check. Bottles are passed in front of a viewing screen as a
final inspection.

Glass failure is usually as a result of thermal shock or impact stresses.
Each glass container has a maximum thermal expansion threshold
and a maximum vertical load stress, which it can withstand without
cracking. These values should be known before it is used for a
particular application.

The shape of the container will influence its strength, smooth edges
result in the formation of a stronger container than one with
rectangular or sharp edges


There are 6 broad classifications of glass defects

1.Checks
2.Seams
3.Non-glass inclusions
4.Dirt, dope, adhering particles or oil parks
5.Freaks and malformations, and
6.Marks


Defects are classified as
•Critical, those that are hazardous to the
user and those that make the container
completely unusable.

•Major, those that materially reduce the
usability of the container or its contents

•Minor, those that do not affect the usability
of the container, but detract from its
appearance or acceptability to the customer.


Critical Defects in Glass Bottles or Containers
1.Stuck Plug. A piece of glass, usually very sharp, projecting inwards
just inside the neck bore
2.Overpress. Is a defect where a small ridge of glass has been formed
on the sealing surface of the finish
3.Split. An open crack starting at the top of the finish and extending
downward.
4.Check. A small, shallow surface crack, usually at the bore of the
container
5.Freaks. Odd shapes and conditions that render the container
completely unusable. Bent or cocked necks are a common defect of this
type.
6.Poor Distribution. Thin shoulder, slug neck, choke neck, heavy bottom
are terms used to describe the uneven distribution of glass.
7.Soft Blister. A thin blister, usually found on or near the sealing surface.
It can however show up anywhere on the glass container.


8.Choked Bore. Here excess of glass has been distributed to the
inside of the finish or opening
9.Cracks. Partial fractures, usually found in the heel area.
10.Pinhole. Any opening causing leakage. It occurs most often in
bottles with pointed corners.
11.Filament. A hair-like string inside the bottle.
12.Spike. Spikes are glass projections inside the bottle.
13.Bird Swing. Is a glass thread joining the two walls of the container


Some Major Defects Commonly Found in Glass Containers
1.Chipped Finish. Pieces broken out of the top edge in the
manufacturing process.
2.Stone. Small inclusion of any non-glass material
3.Rocker Bottom. A sunken centre portion on in base of the
container
4.Flanged Bottom. A rim of glass around the bottom at the parting
line


Some Minor Defects Commonly Found in Glass Containers
1.Suncker Shoulder. Not fully blown, or sagged after blowing
2.Tear. Similar to a check, but opened up. A tear will not break
when tapped, a check will.
3.Washboard. A wavy condition of horizontal lines in the body of
the bottle.
4.Hard Blister. A deeply embedded blister that is not easily
broken.
5.Dirt. Scaly or granular nonglass material.
6.Heel Tap. A manufacturing defect where excess glass has been
distributed into the heel
7.Mark. A brush mark is composed of fine vertical laps, e.g. oil
marks from moulds.
8.Wavy bottle. A wavy surface on the inside of the bottle.
9.Seeds. Small bubbles in the glass
10.Neck ring seam. A bulge at the parting line between the neck
and the body.


TOLERANCE

Tolerances as per GLASS PACKAGING INSTITUTE

CAPACITY 1% for large bottles and

upto 15% for small bottles

WEIGHT generally 5%

HEIGHT 0.5 to 0.8% overall HEIGHT

DIAMETER 1.5% for 200mm & 3% for 25mm


TOLERANCE
The following are examples of some permitted tolerances:
Vertical load control values

Glass bottle Vertical load
Refillable 6000N
Non-refillable 4000N


CAPACITY

Nominal Tolerances Nominal Tolerances
Capacity (ml) (ml) capacity (ml) (ml)
up to and ± up to and ±
including including
100 2.7 450 5.7
125 3.0 500 6.0
150 3.3 600 6.5
175 3.5 700 7.1
200 3.8 800 7.6
250 4.2 900 8.0
300 4.6 1000 8.4
350 5.0 1250 12.5
400 5.3 1500 15.0


BODY AND HEIGHT DIMENSIONS
Height Tolerances
Body/Diameter

Tolerances
D (mm) up to and TD (mm) H (mm) up to and TH (mm)
including ± including ±

25.0 0.8 25 0.7
36.5 0.9 50 0.8
50.0 1.1 75 0.9
62.5 1.2 100 1.0
75.0 1.4 125 1.1
87.5 1.5 150 1.2
100.0 1.7 175 1.3
112.5 1.8 200 1.4
125.0 2.0 225 1.5
137.5 2.1 250 1.6
150.0 2.3 275 1.7
300 1.8


VERTICALITY CONTROL VALUES FOR VERTICALITY

Height H (mm) Tv (mm)
up to and ±
including
120 2.2
150 2.7
175 3.1
200 3.4
225 3.9
250 4.2


MINIMUM GLASS THICKNESS VALUES
Body overall
Diameter (mm) Minimum glass thickness (mm)
Non-refillable Refillable bottles Surface protected
bottles non-refillable bottles

Up to 60 1.1 1.5 0.8

>61 to 71 1.4 1.8 0.9

>71 to 81 1.5 1.9 1.0

>81 to 96 1.7 2.0 1.1

>96 to 110 1.8 2.2 1.3


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