JUDGING THE QUALITY OF VINTAGE GLASSWARE©

If you prefer to begin with THE STORY OF GLASSWARE, click on https://dearfriend.buzz/category/glassware/?order=asc

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 A  fiasco I could have avoided — had  I used my fingers:

In a well-established flea market in an old barn in Connecticut,
I chose six wine glasses with hand engraved birds in flight.
Although the light was dim, each glass appeared perfect until I
washed them at home.  The rim of every glass was rough: they
were probably stored up-side down on a rough surface!

I examined them visually in the barn’s dim light but didn’t run
my finger around the top of each glass.  When I had the rims filed
and polished, each glass shattered.

Venues for resale glass products can be daunting and you’re on your own in flea market, thrift shop, estate sale or charity bazaar.  Be sure to carry a magnifying glass to better read labels and examine each product for flaws. (I didn’t bring one to the Connecticut flea market). Selections are limited, prices erratic, original labeling is probably gone and other information is probably a ‘guesstimate’ of the seller.

How old is the glassware?
Age has no impact on glass quality so have no concern about the age of glass unless you’re buying it for antique value. All glass is vitreous and if there are no cracks, glass cannot hold bacteria. Room temperature glass can be washed in hot, soapy water.

Did you get an honest answer about the age of the glassware?
This is impossible to know unless the manufacturer and style is from a particular period.

How long does glassware last?
Glass vessels from 1,500 B.C. are on display in international museums, so it’s safe to say, until glassware is broken, it has no expiration date.

What kind of glass is it?  soda-glass?  lead crystal?
This is important to establish. Lead crystal is much more expensive than soda-glass unless the soda-glass has historical value. (A manufacturer’s name or brand or logo is sometimes etched on the bottom of glassware.)  Whether free —or mouth blown into a wood mold is not easily discerned—but if the item is expensive, check the Internet for information about the manufacturer even though they may no  longer be in business.

Mold marks diminish the value of all glassware except Colonial and Depression Glass—where mold marks help establish authenticity.

Never purchase a lead crystal decanter to store wine or liquor.
Lead leaches into standing spirits. 

Where was the glassware made?
Currently, almost every developed country produces good quality glassware and traditions of style and quality have made some international brand-name glassware more valuable. If labels remain on the glassware you’re interested in buying, information about the maker might be available on the Internet.    

Is weight significant?
Very thin and sheer glass, or very heavy glass, is a personal preference—but don’t confuse weight with strength. If glassware looks heavy, it should be heavy; if it looks light, it should be light.  Weight must be balanced and not top or bottom heavy, especially for stemware.

Is the clarity good —and the color uniform?
Examine glassware in good light for clarity and uniformity of color, even if it’s clear glass. Don’t be disturbed by minute bubbles, but inconsistent color, flecks (seeds), obvious bubbles, impurities or stria (variations caused by unequal density of ingredients or variations in furnace temperature) are not a sign of good quality. 

Is the glassware well-polished and finished?
Superior quality glassware has polished rims and also polished foot rims—even for soda-glass. Good quality finishing is done by hand—one-piece at a time—which increases the price of each glass. Even if glassware is not hand polished, all rims must be smooth and bases must not scratch table surfaces. Check with your fingertips as well as your eyes.

Glasses with a safedge (the edge is uniformally thicker than the wall of the glass) are mass-produced and because the rim does not require polishing by hand or machine, should be relatively inexpensive.  Safedge glasses are sturdy for everyday, especially for young children. Connoisseurs prefer not to drink wine from glasses with a safedge—and better restaurants do not use them. 

If glassware is decorated, determine if it’s a decal or hand-painted and heat-sealed.
If hand painted designs –or decals of color or gold –have begun to wear,  assume the glassware was washed in a dishwasher. Pass. Even if the design is heat-sealed, decorations last longer if washed by hand.  

Don’t believe everything a seller tells you about glass products:
Many people confuse pressed glass with cut glass and engraved glass with etched glass. They look similar but their production techniques and market value are very different. 

Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST IS:  THE STORY OF FLATWARE

HOW DO YOU KNOW IF THE QUALITY OF GLASSWARE IS GOOD?©

 

If you prefer to begin with THE STORY OF GLASSWARE, click on https://dearfriend.buzz/category/glassware/?order=asc

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QUALITY DENOMINATORS OF GLASSWARE:

IDENTIFY THE RAW MATERIALS:
Know if the glass is soda-lime, borosilicate or lead crystal (the most expensive).

If it is lead crystal,  check for the lead percentage — which should be on the label or available from the retailer. If answers are unsatisfactory and/or questionable, don’t hesitate to contact the brand manufacturer.

PRODUCTION METHODS:
Mouth or machine? Mouth-blown or free-blown soda-lime or lead crystal glassware does not have mold marks.  Mold marks are a sign of pressed or molded machine-made glass. If not too visible, mold marks are not objectionable — but the price of the glassware should be relatively low because of little or no hand-labor for polishing.

No visible mold marks on machine-made glassware means the manufacturer has ground them away and then polished the surface by hand or machine — which adds to the price.

FINALLY:
Examine each of the following elements of finished glassware and  judge for yourself if standards of production quality have been well executed.

Rims:
Rims must be smooth, polished and of uniform thickness with the walls of the glass. Glass walls may range from very thin to rather heavy depending upon the style. Lead crystal glasses will always feel heavier and be relatively thick.  Choice of weight and wall thickness is personal. Wine connoisseurs prefer a polished, thin rim to better direct the flow of wine and enhance the complexity of a fine wine.desktop safeedge

An exception to uniform thickness of walls and rims are glasses made with a safedge–-made by passing the open cut edge of a glass under a flame until the edge quivers and melts into a rounded, thicker rim.  

Glasses with safedges should be inexpensive because they don’t require polishing. Safedge glasses are more durable for children and everyday use; they’re not preferred for fine glassware.   All glasses should be stored upright to protect their rims.

Bases:
Glasses must sit firmly and feel balanced.  Check the bottoms of all glass products to make sure the ‘sitting’ edge of each will not scratch your table.  Grinding and polishing glass ‘bottoms’ by hand or machine is labor intensive —but expected if purchasing better mouth-blown glasses. Unpolished glass bottoms are acceptable if smooth to your touch–but should cost less.

Clarity:
Minute bubbles signify glassware is free-blown—and they’re acceptable.  But glassware must not have flecks (seeds), obvious bubbles, impurities or stria  (variations in glass caused by unequal density of ingredients or variations in furnace temperature). Better quality manufacturers destroy production having any of these defects.

Moderately priced, heavy,  mouth-blown glassware made in Mexico — from recycled glass —is currently popular. It’s full of tiny bubbles that give it a hand-crafted charm.

Color:
Whether free-blown or machine-made, colored glass must have uniform pigmentation whether transparent, translucent or opaque.  Lack of uniform pigmentation indicates that the silica and other ingredients had not been brought to proper fusion temperature in the glass furnace.

Weight:
Don’t confuse weight with strength. If a glass product looks heavy, it should be heavy. If a glass product looks light, it should be light.  Weight must be balanced and not top or bottom heavy, especially stemware.

Stems:
If you are buying good stemware, be sure all joinings of bowl to stem to base —are invisible.

Care:
1.  Glassware should be *room-temperature when washed in warm, soapy water.

2.  Take special care rims do not touch each other.
3.  Wash cut lead crystal stemware by hand because swishing hot water and dishwasher detergents eventually build-up a milky residue.
4.  Dry with lint-free cloths.
5.  Store glasses right-side-up to protect rims from rough surfaces.

I can’t forget the customer who brought a box of crystal
shards to the Gift Gallery and asked for me. She had
purchased an expensive silver champagne stand with a
heavily-cut lead-crystal ice bucket trimmed with silver.
After her party, she emptied the ice and plunged the *cold,
crystal ice bucket into hot soapy water:—IT EXPLODED!   

There are considerations in caring for all products but the
manufacturer had not provided care instructions for the

crystal ice bucket: it was NOT the customer’s fault!  

Relieved no one had been hurt, I credited her account but
never 
carried the item again.

 Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST: VINTAGE GLASSWARE

DRINKWARE: STEMWARE and TUMBLERS©

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 STEMWARE

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Glasses having a bowl and foot—separated by a stem—are called stemware. Stems can be short, tall, plain, faceted, colored or embellished; some stems are shaped to encase an ornamental tear-drop bubble of air.

Stems are designed for holding—so one’s hand temperature won’t affect the temperature of wine or other beverages to be sipped from the bowl. Therefore, stems must be sturdy.

Stems can be shaped from a separate gather of molten glass and then stuck to the bowl and foot while each part is still hot— or stems can be drawn (or pulled) from the gather of molten glass from which the bowl is shaped — then attached to the foot while all parts are still hot. Stuck or drawn, seamless attachment of stems to both bowl and foot is an indication of good quality.

 STEMWARE SHAPES AND SIZES:

Round, straight or flared bowls of stemware are made to please all preferences. Glass producers usually market suites for each shape in sizes suitable for each beverage. Approximate capacity:
water:               12 to 17 oz
champagne:     6 to   8 oz
brandy:              2 to 25 oz
cocktail:             4 to   9 oz.
cordial:               2 oz.
wine:                   Capacity varies according to each varietal.

WINE GLASSES:

My brother gifted me with wine tasting classes at NYC’s Four Seasons restaurant. Our instructors were well-known, international wine experts. Before our ‘first tasting’—they emphasized how the size and shape of a glass changes one’s taste and perception of different varietals.

To prove this, we were given different sizes and shapes of stemware for tasting different red and white varietals — including sparkling wines. We were quickly convinced of the difference and importance of using correct glasses for ultimate enjoyment of each wine.

Storage for a variety of wine glasses is a problem
for many of us but ‘all-purpose’ wine glasses are
not a solution;  I consider them ‘marketing spin’.

CHARACTERISTICS OF GOOD WINE GLASSES :

  • A sheer transparency to enjoy the color of the wine
  • A fine polished thin lip for aesthetic pleasure
  • A sturdy stem for holding
  • A secure base for proper stability
  • A rounded bowl with thin lips and poured only 1/3 full— to allow the wine to be properly swirled in order to capture the bouquet and examine the ‘legs’ of the wine. Our instructors felt Americans ‘over pour’  wine because they don’t want to appear cheap.

Regarding shapes:
George Riedel of the renowned Austrian glass company writes: 
“Every shape is especially engineered  to shape the flow of the wine into the mouth, delivering it to a precise part of the tongue in order to give specific sensations—the shape not only changes the taste of the wine, it shows different elements of the bouquet.”

There are shapes and sizes of both lead-crystal and soda-glass stemware to please all tastes at all prices. Most manufacturers produce table-setting suites with glasses for water, different varietals of red and white wine and for dessert or fruit. Other popular shapes are usually available in a broad range of sizes.

Despite marketing pressure to buy glasses of the same suite,
water goblets and wine glasses don’t have to match;

In fact, cocktail, martini, and champagne glasses seldom match
table stemware. Mixing stemware shapes and styles —depending
upon each beverage—creates more interesting table settings!

Stemmed glasses with saucer shaped bowls were originally made for champagne. Today, saucer shape is suggested for fruit and ice cream;  flute shaped glasses better contain and maintain champagne bubbles.

2 champagne glasses

Changing all table settings in the Gift Gallery every two weeks was great fun.I was able to choose linens, dishes, glasses, flatware and accessories from our international collections.

When I saw very tall and very purple stemware cased with white in a New York showroom, I envisioned striking table settings— and ordered them in every size.

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The distinguished importer suggested—very politely—that I order the purple glasses for water and dessert only and order all wine sizes of the same shape in clear glass—to better savor the color and clarity of the wine.

Customers loved the purple glasses:
even more, they loved that everything didn’t match!

TUMBLERS

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Glasses without stems are tumblers. It’s suggested the name came from glasses made with a convex base —to force glasses to be emptied before being set on a table—when of course, they’d tumble.

Capacity of basic tumblers:
Hi-ball or water :                12 to 18 oz.
Old-fashioned or juice :     7 to 12 oz.
Double old -fashioned:     12 to 16 oz.
Pilsners:                                17 oz.

From aperitifs to cordials, glasses for red wine, white wine, rose‘, champagne, sherry, martinis, manhattans,  whiskey sours,  margaritas,  cosmopolitans, piña coladas, Campari, Kir, ouzo, et cetera are designed to enhance the pleasure of each of these traditional, international wines, spirits and mixed drinks. However, specific shapes and sizes of glasses for serving specific drinks may differ from country to country—restaurant to restaurant.

Brandy drinkers sniff  brandy and snifters come in all sizes. Some beer drinkers like to drink from the bottle but beer mugs and pilsner glasses turn beer into a special occasion. The tradition of green stemmed glasses for Rhine wine prevails centuries after they were made to detract from a ‘greenish wine’ due to incorrect mixing of grapes; but why not use their unique size and shape for cocktails?  

Before drinking, we raise our glass and offer cheers!
au votre santé! bottoms’ up!, tchin tchin!,  Prosit!,
Skål!, Salute!;  then—‘clink’ our filled glasses in
fellowship.

Glasses for specific drinks are available from molded soda-glass to mouth-blown soda-glass and mouth-blown lead crystal, which cost the most and ‘clink’  the clearest.  Paper and plastic glasses don’t ‘clink’.

WHICH DO YOU BUY?
There’s plenty of tradition: no rules.

  1. Are you likely to entertain formally or informally?
  2. How important is it for you to have the ‘correct’ glass for each drink?
  3. Assess your storage space.
  4. Plan what you can spend and choose two to four ‘drinks’ you commonly serve (e.g. red wine, white wine, beer, champagne).  Select glasses you like and can easily replace.
  5. Want more?   Try stemware with wiggly stems—in funky colors—and start a trend!

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 Have fun.

 Pat Breen: EYEWITNESS TO QUALITY

My next post: JUDGING THE QUALITY OF GLASSWARE 

CHANGING THE SURFACE OF GLASSWARE © 

 

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HAND-CUT LEAD CRYSTAL

CUTTING LEADED CRYSTAL
Hand-cutting showcases the art of artisan glassmakers who guide and press lead crystal blanks against carborundum and sandstone wheels to grind grooves and/or facets in cooled lead crystal to create a design.

Water constantly trickles over cutting wheels to prevent them
from becoming hot enough to break the crystal.  Without lead
content, the cutting wheels would probably shatter the glass
.

Waterford biscuit and 007

Producers of better quality hand-cut lead crystal hand-polish cuts by guiding each cut against wheels of increasing fineness: stone, then lead, wood and cork and finally a mixture of water and fine powder.

Producers of lesser quality lead crystal polish cuts by dipping cut crystal into acid. Side-by-side, the difference is significant.

ENGRAVING

Glass engraving originated as artisan hand work and is not as invasive as hand-cutting.  Both lead crystal and soda-glass can be engraved by guiding blank glass against revolving copper wheels that grind fine wheel marks into the glass, leaving a soft grey design.

Engraving is still done by hand but more commonly by machine.  Machine engraved monograms on glassware is both popular and affordable.

ETCHING

Acid, applied by hand or by stencil for mass-production, bites or ‘etches’ into glass leaving a frosted design deliberately left unpolished. Etching resembles engraving but leaves no wheel marks on the glass.

SANDBLASTING

A stenciled design is placed on glass to protect areas to remain untouched — and expose areas to be blasted away by a force of sand— leaving a textured design.

 METALLIC TRIM

venice 14 (2)Gold, silver or nickel metallic oxides are applied to glass by hand or machine and must be fixed in an annealing oven—-and always washed by hand.

MERCURY GLASS

A film of mercury is poured between double walls of glass to look like brilliant silver.

 PAINTED GLASS:  

more pics for book 033Enameled glass is painted with oxides mixed with finely powdered glass suspended in oil. The design is permanently fixed in a low temperature muffle kiln. If paint pigments are not fixed with heat, they’re considered ‘cold colors’, which eventually wear off.

 DECALCOMANIA

Decals are designs printed on film-coated paper with special paint which may be colorful and/or metallic. The paper designs are applied to the glass and fixed with heat in a process similar to ironing a decal on a t-shirt.  Decals are commonly used to decorate barware and colorful glassware for children. 

TRANSFER PRINTING

This technique requires a design to be first engraved on a copper plate which is inked. The ink is then transferred to paper and applied to the glass while the ink is wet.  The same copper plate is used for duplication. All transferred designs on glass must be fixed with heat.

Even if fixed with heat, all glassware with applied ornamentation that is: metallic, painted, decals or transfer, should be washed by hand.

 Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST:  DRINK-WARE: STEMWARE & TUMBLERS

 

 

COLORED AND CASED GLASSWARE©

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Venice travel

 All glassware pictured in this post was hand/mouth blown in Murano.

Glassware shaped by mouth or mold can be transparent, translucent or opaque and made in every color of an artist’s palette — and a variety of techniques combine colors in wondrous ways.

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COLORED GLASS

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Colored glass is made by mixing non-metallic elements as sulphur and selenium and metallic oxides as copper, antimony, manganese, iron, nickel, cobalt and gold into batches of glass ingredients prior to fusion in a glass furnace.

Cobalt and ruby red are more expensive to make than other colors because oxides to make these colors are more costly.

CASED GLASS

venice for blog 9.MHT
Colors of hot molten glass,
layered over each other during shaping,
are cased glass.

Overlays of color may be transparent, translucent or opaque and of different thicknesses. If the top layer of glass is transparent, or if portions of the top layer are cut away, lower layers of color are revealed.

PATTERNS MADE FROM GLASS THREADS:

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Threads of varying thickness are fused into multi-colored canes, sliced and embedded under clear molten glass.  Artisan glassware made from glass rods are a Murano specialty.

FILLIGRANA

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Lace-like patterns are made by combining and twisting glass rods so thin,
they’re called ‘threads’.

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This paper weight design is millefiori, (1,000 flowers)– a classic design  made from slices of colored canes made from glass threads embedded under clear glass.

From the 1870s through the 1920s,  extraordinary contributions in the design and execution of glassware were made by  Louis Comfort Tiffany, an American master of decorative arts who achieved glass colors and textures still unsurpassed. His stained glass windows, lamps, mosaics and Favrille glass are featured in the American Wing of the Metropolitan Museum of Art.

Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST:  THE SURFACE OF GLASSWARE

SHAPING HOLLOW GLASS©

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 ANCIENT GLASS SHAPING TECHNIQUES:

Egyptians poured hot liquid glass around a core of clay or sand to create hollow vessels to hold precious oils and perfumes as early as 1,500 B.C.  All glass was translucent or opaque. Clear glass was not developed until the 1,500’s A.D.

Blowing air through a pipe to inflate molten glass originated in Syria in the first Century B.C. Making hollow glass vessels began to flourish throughout the Roman Empire. 

SHAPING GLASS TODAY:

At glass factories, silica and other glass ingredients are sieved and mixed with scrap glass called cullet.  Cullet comprises 1/4 to 1/2 of a new batch of glass because it helps ingredients fuse faster and is used as a starter to save fuel. This ancient technique of using scrap glass is an example of true recycling.

All ingredients are mixed in large pots and placed in furnaces in the afternoon to achieve proper temperature and fusion for the next morning’s production. Fusion takes place at 2,700-3,000º Fahrenheit.  In Murano, workers begin their work day at 6:00 A.M because factories get very hot in the afternoon. The first glass furnaces heated with wood, (the reason glass factories were near forests): oil replaced wood,  then methane, natural gas and electricity.

glass furnaces

Over 400 large glass-melting furnaces in the U.S currently employ an energy-saving technology of oxy-fuel firing.

FREE BLOWN:

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The gaffer (master glass blower/artisan) blows air through the blow-pipe into the molten-metal and presses simple iron paddles and calipers against the billowing taffy-like glass to define a shape. The blow-pipe is constantly rotated to prevent sagging due to gravity.

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As molten glass is shaped, it’s reheated frequently to maintain a workable temperature which the artisan team  judges only by color.  Finished shapes are cooled slowly to prevent crystallization.

shattering glass

Watching a team spend more than 30 minutes developing a large mouth-blown shape, the gaffer shattered it because it was not up to his standard of excellence. The blown shape probably had large bubbles or striations  (visible streaking). Minute bubbles in mouth-blown glass are quite acceptable, large bubbles are not.

 MOLD BLOWN:

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Molds are used to create uniform shapes and sizes for soda glass, lead crystal or borosilicate glass. Any of these molten glass formula can be mouth blown or machine blown into molds for mass-production.

Metropolitan Museum glasses

Products shaped in cast-iron molds usually have mold marks whether mouth or machine blown. Mold marks lessen the quality and value of glassware. Manufacturers of better soda-glass products usually grind mold marks away;an acceptable practice.

mold blown glasses

Soaked wooden molds are used to shape better quality glasses because hot molten glass in soaked wood creates steam—and steam prevents mold marks from developing.

SAFEDGE:

SAFEDGE

Mouth-blown tumblers can be mass-produced by mouth-blowing molten metal into iron molds, used to shape tumblers one-at-a-time.  Where a tumbler is attached to the blowpipe, the closed end is cut open by machine, leaving a very sharp edge. 

As glasses pass beneath an intense flame with the cut edge face-up, the sharp-edge quivers, melts and thickens to become a smooth ‘safedge’.  Glasses with a safedge are inexpensive; they require no polishing by hand or machine.

PRESSED GLASS:

Pressed glass was patented in 1825 by John Bakewell, an American, who developed a way to make pressed glass knobs for furniture.  Mechanical glass pressing machines soon led to the global mass-production of inexpensive decorative glassware.

Gathers of molten-glass are plunged into molds to form the outside shape or bottom of a product. Before the molten-glass solidifies, a second mold presses down to shape the inside or topside of the glass shape. This process allows for mass-production because it requires little or no hand labor for production or finishing—and making it affordable.

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Molds impart texture to help offset inevitable mold marks.  Pressed glass replicates the texture of ‘cut glass’ but has its own charm— even with mold marks—although some manufacturers grind the mold marks away (adding to the cost).

Antique Colonial and Depression pressed glassware is highly valued by collectors but mold markings are essential for authenticity. Mold marks are retained in replicas of Colonial and Depression glassware but labels must state that they’re reproductions.

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A soda-glass cake plate is being mass-produced as calibrated amounts of molten glass drop onto a rapidly rotating mold.  A top mold is pressed down to control the shape and texture of each plate. A conveyor belt carries each hot plate through an annealing oven where it cools slowly to prevent cracking.

Texture eliminates any need for polishing and the plates can be immediately boxed for shipping.  Costly technology is offset by minimum hand-labor and volume sales;  an example of economies of scale .

Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST :  COLORED AND CASED GLASS

KINDS OF GLASSWARE©

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GLASS IS A PARADOX

This vitreous matter can be
transparent, translucent  or opaque,
delicate or strong and
functional or decorative.

Throughout glass history, diverse glass formulae enabled artisan glass blowers, cutters and engravers as well as mass-producers of glasswares to enrich our lives.

Decorative and functional glass shapes are created by
hand/mouth,
mold or machine
and embellished with cutting, etching and engraving
by hand or machine in broad price ranges.

HOW DO WE KNOW IF GLASS WARES ARE GOOD?

Glass wares are as good as the raw materials
and production methods used to produce them.

Sand is fused with specific ingredients to become soda-glass, lead crystal or borosilicate glass (used in laboratories or as cookware).  We cannot assess the quality of artisan or mass-produced glass without transparency of raw materials and production methods on all labels.

SODA GLASS:

Non-leaded glass (most of our everyday drinkware) is made of various compositions of soda glass. Venetian soda-glass was ‘greenish’ until the middle of the 15th Century when a method of purifying soda ash was developed. The result was glass so clear and colorless it was called cristallo because it resembled rock crystal. Even though many bridal registries refer to all stemware as crystal—the word implies lack of color, it is not a formula of glass.

Melting pure silica requires temperatures higher than commercially practical. Alkalis, soluble salts as soda and potash may be added to reduce the fusion temperature of silica.

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Ingredients commonly added to silica:

SODA:    an alkali of sodium carbonate (usually ashes of dried and burned marine plants) which serve as a flux to reduce the fusion point of silica.
LIME:     makes glass more stable, lighter, cheaper and cool faster.
POTASH:  burned beech wood, oak or fern is substituted for soda to make glass harder, more brilliant and capable of being cut and/or engraved (not to be confused with lead crystal).

LEAD CRYSTAL:

In 1676, English glassmakers introduced lead oxide as a flux in potash-lime glass to create glass with exceptional clarity and brilliance: marketed as lead crystal. Lead crystal is heavy, colorless, brilliant, and refracts and reflects light. It has a distinctive musical tone when the edge is flicked with a finger or struck with a pencil.

Lead oxides makes glass ‘softer’ — which makes it easier to cut and engrave but easier to shatter.

Producers of lead crystal usually list the percentage of lead oxide although exact formulae are guarded secrets.

To qualify as lead crystal, international guidelines require a minimum of 10% lead oxide. Steuben Glass (no longer made: still revered) used a platinum lined melting tank and stirring rod because platinum resists corrosive effects of molten lead crystal and imparts no impurities to the lead crystal formula. 

Lead Crystal Quality Designations:
Half-lead  requires a minimum of 24% lead oxide.

Full-lead  requires a minimum of 30% lead oxide. (cristal superior)

CAVEAT:
Never store wines and spirits in lead crystal decanters.
Lead increasingly leaches from lead crystal into wine or spirits.

BOROSILICATE GLASS: 

Made with boric acid, borosilicate glass, invented in the 1880s by German scientist Otto Schott, was used for heat resistant laboratory and cooking glass.  It does not expand with heat or cold but cannot pass from freezer to oven.  Silica content is usually from 55 to 80%.

In 1915, Corning  introduced a clear,  low-thermal-expansion borosilicate glass for laboratory glass and kitchenware; trademarked PYREX; (each letter is uppercase).

Spun off from Corning in 1998, World Kitchen, LLC,  licensed the name Pyrex (not upper case) for kitchen products.  Pyrex is not borosilicate glass. 

World Kitchen’s Pyrex is *tempered soda-lime glass .
It is cheaper to make than borosilicate glass, not as
heat resistant and can break from heat stress.

*tempered glass is a safety glass of increased strength / as compared to normal glass.

N.B.  Confirm HEAT–RESISTANT PROPERTIES for all borosilicate glass.

WE KNOW WHAT WE LIKE:  HOW DO WE KNOW IF IT’S GOOD?

Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST:   SHAPING HOLLOW GLASS.

 

THE STORY OF GLASSWARE©

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Read how glassware originated
and how glass wares are still artisan and mass-produced
—from raw materials to finished products.

Standards of quality from
international experts at renowned glass factories will help you
JUDGE FOR YOURSELF! 

Brands change, styles change, prices change.
TIMELESS, UNBIASED,  GENERIC STANDARDS OF QUALITY
FOR EVERYDAY PRODUCTS DO NOT  CHANGE.

 EVERYDAY HOME PRODUCTS explains my mission  ABOUT is about me.

Glassware is ubiquitous and glassware breaks,
yet we all love glassware and stand in awe of
man’s magical transmutation of glass from sand!

Our lives are enriched by the function and beauty of glassware in our homes but today’s choices are confusing. Many styles and shapes of glassware are similar to each other and the price range is very broad.

It’s almost impossible to buy inferior glassware although we may not like the color, shape, weight and size of some products. We have no money to throw away but many of us don’t know how to identify and differentiate qualities that make some glasses superior to other glasses.

We”ll explore timeless, generic principles of quality from designers and technical experts at international artisan and mass-production glass factories. Diverse formulae provide diverse glasswares for drinking and cooking but each product is only as good as the specific raw materials and production methods used to make it. It’s impossible to assess artisan or mass-produced glass without judging these elements.

Historian Jacques Barzun wrote;
“Without a sense of history,
the feeling is given that the whole system  drowns  down ready-made from the skies.” 

And so, we begin our story of glass.

Obsidian is natural glass formed when a thick volcanic lava flow, rich in silica, cools into a brown-black, vitrified material.  More than 11,000 years ago, prehistoric people quarried obsidian from a cliff near Mammoth Hot Springs, Wyoming and fashioned it into tools and weapons.

We don’t know how man-made glass came to be but we marvel
that early man made glass from sand more than 4,000 years ago.
The essential ingredient of man-made glass is silica (found in
nature as sand) and melted at extremely high temperatures and
shaped and cooled to a vitreous (non-porous) state. Historians
question if a very hot cooking fire on a beach might have fused
sand with soda?

We may not know how man-made glass came to be but we do
know glassware history chronicles man’s history. Early glass
wares were made using solid core, mold-casting and carving
techniques. Solid glass beads were made in 2,500 B.C. and
Egyptians poured hot liquid glass around a core of clay or sand
as early as 1,500 B.C to make vessels for precious oils and perfumes.

Blowing air through a pipe to inflate and shape a glob of molten glass attached to the opposite end is believed to have originated in Syria, 1st Century B.C.   The production of hollow glass vessels flourished throughout the Roman Empire until its’ decline, circa 476 A.D. All glass was translucent or opaque: clear glass had not yet been developed.

Venice for blog 1.MHT (2)

Venice, an independent state on the Adriatic, became a crossroad of sea trade. Inspired by glass wares originating in the Middle East, 13th Century Venice became a center of glass-making. The Venetians crushed quartz river pebbles for pure silica which they combined with soda ash from Mediterranean coastal plants. Danger to wooden buildings from glass furnace-fire forced the glass industry to move to the nearby islands of Murano and where it remains.

In the early 1600’s, the heavily forested Virginia colonies provided wood for the intense furnace heat required to fuse ingredients for making glass and glass-making became America’s first industry. By the 1950’s, glass-making was still a regional industry but unemployment, especially in West Virginia, was very high.

During his presidential campaign, Jack Kennedy pledged to create jobs in this area. Mrs. Kennedy honored his pledge by ordering stemware for the White House from West Virginia:  the very glasses we sold in Berger’s Gift Gallery.

Buying trips to Murano always put me in an eight century time-warp; factory showroom windows provided sights even more magical than the glass wares!

venice port (2)

Glass ingredients were batched in pots each afternoon and placed in special furnaces to achieve a high temperature for proper fusion for the next day’s production.  The result was a fused hot mass called ‘molten metal’ —shaped and cooled slowly to become glass.

I never dreamed I’d return to Murano as an FIT professor and revisit world-renowned glass factories to interview management and artisans whose very breath creates the beauty of glass.  Artisan production hadn’t changed.

I later visited several mass-production glass factories in other locations in Italy. Furnace technology was similar; some had modifications and even the iron paddles and calipers were similar to ancient tools.

Glassware production is currently global—although competition from low wage countries and rising costs of raw material and labor have forced many international manufacturers out of business. Mergers, bankruptcy, buy-outs and reorganizations chronicle their struggle to survive. My sorriest example: NYC.’s 5th Avenue isn’t the same without Steuben Glass.

I never cease to marvel at the vitreous material that protects us from the elements, enhances beverages and helps us explore our world via test tube, microscope and telescope.

The next time you put on eyeglasses,
look in a mirror—or sip champagne,
imagine your world without glass.

Pat Breen: EYEWITNESS TO QUALITY

MY NEXT POST IS:  KINDS OF GLASSWARE

GLASSWARE POSTS—FROM FIRST TO LAST:
The Story of Glassware©
Kinds of Glassware©
Shaping Hollow Glass©
Colored and Cased Glass©
Changing the Surface of Glass©
Drinkware: Stemware and Tumblers©
How do you know if Glassware is good?©
Judging the Quality of Vintage Glassware©