Lead Oxide: Exploring the difference between glass and crystal

In light of our visit to ColleVilca where we learned about the chemistry of glass and glass blowing methods, I began to question what makes crystal more valuable than glass. From my understanding, what differentiates the two is based primarily on lead oxide content, crystals ranging from 24-27%. Anything slightly under this amount would be considered lead glass while anything higher could be potentially poisonous for us to use. What is intriguing though is that this small range in chemical composition is enough to make the difference between a prized item and one that is overlooked. If glass and crystal and virtually identical to the untrained eye then there must be some reason why crystal is so much more desired and expensive. So, I asked our guide what it was about crystals that made them so different from glass and why it is more valuable. I was hoping for some magical property or characteristic unique to crystals but, much to my dismay, she referred back to lead oxide content. She said lead oxide is very expensive to use so the more you have in your product, the more valuable it is.  A little research, however, and I find there is a lot more to lead content than I thought.

Crystals are a type of glass, meaning all crystals are glass but not all glasses are crystals. The concentration of lead necessary to constitute something as a “crystal” varies from region to region. In the United States, having 1% lead oxide incorporated into production of glass is enough to give a product the “crystal” name. In Europe, there is a standard for making glass/crystals but the range is much larger than the one set by ColleVilca. Here is a breakdown of lead content and what this means in terms of defining glass in Europe.

glass ware=  4-10% lead content

lead-glass= 8-10% lead content

crystals=  10-30% lead content

lead crystal= >30%

The presence of lead oxide in important because it hardens the glass, making it easier for artisans to exquisitely cut and engrave it. More importantly, lead has intrinsic properties that make objects sparkle. Glasses with more lead oxide content have more sparkle, meaning they can diffract light better. Regular glass with little to no lead content cannot diffract light, whereas fine crystals are capable of casting “color spectrums though a whole room” in the presence of light. Certified Vilca crystals, which are guaranteed to have over 24% lead content, are made with a very high refractive index of over 1.56. The presence of lead adds more weight to the final product, making crystals heavier than regular glass. This is not to say that, however, they are sturdier. Incorporating “lead into glass reduces the ‘give’ in the glass,” actually making it more fragile and brittle. In regard to atomic structure, crystals are arranged in a highly ordered and repetitive manner whereas arrangement in glass is random. This is why the sound produced when you flick a crystal produces a much more dainty and long-standing "ding". 

Below is an image highlighting the structural difference between glass and crystal:

So, like I had thought, there is more to lead oxide than it’s price. The presence of lead gives crystal physical properties that make it more desirable than glass. Higher levels of lead oxides means better cuts, more intricate design, more sparkle, more weight, and of course, more delicacy. The art of glass-blowing at ColleVilca was indeed a sweaty and arduous process but the result? Priceless.

Sources:

http://www.grandinetti.org/resources/Research/Applications/OxideGlassStudies/GlassStructure.gif

http://www.ehow.com/list_6299129_differences-between-glass-crystal-glassware.html

http://vspages.com/glass-vs-crystal-23591/

http://www.luckyglass.cz/en/crystal_glass.html

http://www.differencebetween.net/object/difference-between-crystal-and-glass/

http://www.vilca.it/en/tips-for-crystal

http://www.kinsalecrystal.ie/history.htm

To inhale or not to inhale

Anahita Sattari

Among the things I have noticed during my stay in Italy, like how the people emit an air of elegance and grace, is how it almost always seems to be in the midst of a puff of smoke that encircles the crowd. Smoking seems to be a fashion trend that never goes out of style. It’s as if the cigarette in the hand is an accessory much like the high heels and designer sunglasses everyone is adorned with. Smoking doesn’t discriminate in Italy. The adolescent, elderly, female, and male populations smoke alike. What’s more, the effects of smoking are not specific to smokers as non-smokers are exposed to 250 harmful chemicals, 69 of which cause cancer according to the National Cancer Institute.  Secondhand smoke is composed of smoke given off by a tobacco product and the smoke exhaled from a smoker. It is almost impossible to avoid any exposure to secondhand smoke when roaming the Vias in Italia.  This is a problem as lung cancer is a result of inhaling secondhand smoke.  

The negative health effects that cigarette smoke yields do not deter smokers from inhaling. So it seems unlikely that they will quit, even when inhaling is at the expense of another’s, aka a non-smoker, health.

Studies to determine to the extent of the effects of smoking on smokers and non-smokers are being continued.

It was found that a polymer is capable yielding superoxide from the reduction of molecular oxygen, which will ultimately convert into hydrogen peroxide and hydroxyl radicals. There are radicals in the tar and gas phase of cigarette smoke. The latter phase consists of oxygen- and carbon-centered radicals which are more reactive than those of the tar-phase. The radicals in the gas phase are produced from the oxidation of NO to NO₂.  

The following are some of the toxic chemicals that are present in secondhand smoke: ammonia, butane, carbon monoxide, chromium, cyanide, formaldehyde, lead, and polonium. It seems unfair that we, the nonsmokers, are put at risk because of the nicotine addictions of the smokers. Furthermore, there is no safe level of secondhand smoke, so any exposure is damaging. It seems that Italy should follow countries like France, Ireland, New Zealand, Norway, and Uruguay, which require places of work including restaurants and bars to be smoke-free.

Too Much Fun in the Sun

            After spending last weekend in Vernazza, a small sunny town in the Cinque Terre, I came back to Siena rather severely sunburned. Parts of my skin glowed painfully red and any movement or touch was excruciating for a few days after. And you may be wondering why I didn’t apply more sunscreen to begin with, instead of trying to find aloe in a nearby farmacia, which entailed explaining my problem with hand gestures and some revealing of my skin. The problem, or one problem rather, was that I didn’t feel or see my sunburn until hours after leaving the seaside. It turns out that this is a normal phenomenon – skin can turn red 2 to 6 hours after the initial burning.

            So some basics: Sunburn is caused by UV radiation from the sun burning the skin. The ultraviolet radiation from the sun is divided into three categories – A, B, and C. While the atmosphere, specifically ozone, filters out almost all of the C subtype along with some A and B, enough UV radiation reach the earth’s surface to cause burns. The burn will develop for up to 72 hours after the initial exposure and pain is generally worst 6 to 48 hours after, followed by peeling skin 3 to 8 days afterwards. Additional symptoms of sunburn can include tenderness, blistering, rash, fever and nausea – these symptoms are caused by the dying cells releasing toxins and when many cells die, they peel off. In extreme cases, hospitalization may be necessary for the treatment of sunburn.

            Although all of the immediate effects of sunburn are extremely unpleasant, the worst problem caused by sunburn is DNA damage. The radiation causes both direct and indirect DNA damage to skin cells, which can lead to skin cancer. The direct DNA photo-damage (or damage caused by light) occurs when the UV light excites the DNA molecule and, within one picosecond, that energy is released. This energy causes the formation of a bond between two thymine bases, as seen in a study by Kohler et. al. In the study, researchers created special strands of DNA with only thymine bases and observed the chemical reaction induced by UV radiation in which the base pairs dimerise when they are in the right conformation. Due to the speed of the reaction, even the rapidly moving DNA molecules appear frozen during the time in which the photo-damage occurs. This damage impairs the replication process - but don’t worry too much, our cells are capable of healing themselves up to a certain point. Problems are more likely to happen when sunburn and DNA damage are frequent; in fact, chronic damage is believed to be a cause of cancer causing mutations.

            A tan, on the other hand, is the body’s protective response to sun exposure. Skin cells produce a substance called melanin, which absorbs solar radiation. There are two types of melanin produced by cells: red pheomelanin and a very dark brown eumelanin. Both types of melanin cause the darkening of skin color after sun exposure. UV-A and UV-B radiation cause two different processes in the development of a tan. First, UV-A radiation causes the oxidation of existing melanin which causes it darken. In addition, stored melanin is released into the cell. This mechanism does not increase the amount of melanin in the skin so there is also no increase in protection against sunburn. The second process, initiated by UV-B radiation, causes an increased production of melanin, through the process of melanogenesis. This is a reaction to direct photo-damage, as discussed previously, and is protective against future UV exposure.

So the major lesson learned: even if you don’t feel the sunburn happening, wear sunscreen because you’ll probably start turning a lovely red within the next 6 hours.

Sources:

http://www.chemistrydaily.com/chemistry/Sun_burn

http://researchnews.osu.edu/archive/dnaburn.htm

http://en.wikipedia.org/wiki/Sun_tanning

http://homeremedieshealth.com/home-remedies-for-sunburn/

It's About Time...

In commemoration of one month of successful living in Italy (and so we can fully live our last few days here), I thought I'd post some useful Italian words and phrases.

This isn't the most chemistry-oriented blog post (I'll make it up with my next one, don't worry!) but I figured we can try integrating the language in our everyday interactions with our fellow neighbors, students and gelaterians. And I can stop trying to speak Spitalian (Spanish+Italian) with them!

First off: Pronunciation

C
=”K” before a, o, u and consonants

=”CH” before e and i

Ex. Ciao!

G

=”GAH” like in “good” before a, o, and uand consonants
Ex. in Good

=”JAH” like “general” before e and i

 

H is silent.

For other letters, it's generally safe to read it as it sounds.

 

Numbers are infinitely helpful, I’ve realized.

1	uno	11	undici	21	ventuno	31	trentuno
2	due	12	dodici	22	ventidue	32	trentadue
3	tre	13	tredici	23	ventitré	33	trentatré
4	quattro	14	quattordici	24	ventiquattro	40	quaranta
5	cinque	15	quindici	25	venticinque	50	cinquanta
6	sei	16	sedici	26	ventisei	60	sessanta
7	sette	17	diciassette	27	ventisette	70	settanta
8	otto	18	diciotto	28	ventotto	80	ottanta
9	nove	19	diciannove	29	ventinove	90	novanta
10	dieci	20	venti	30	trenta	100	cento

Oh, what about those greeeetings?

Ciao: casual, “hello”
Buongiorno: “good day”, formal, use in morning and early afternoon
Buono sera: “good evening”, formal, use in evening into the night
Arrivederci: “goodbye”

Ooo, I’m doing well. And you…?

Come stai? How are you?
Come va? How are things?

If we're talking to more than one person we say…

Come state? How are you?
 

Respond with…

Bene, grazie. E lei? Good, thank you. And you?
Benissimo. E lei? I’m very well, and you?
Non ce male. Not bad.

My name is…

Mi chiamo . . . My name is…
Come ti chiami? What’s your name?
Piacere - pleased to meet you

For nationality, you can use “Sono”

Ex.
Sono italiano/italiana
 

I would like a… (At a restaurant)

Caffé: a small and mighty shot of espresso
Latte Macchiato: milk with very little coffee
Cappuccino: cappuccino

Prendo un cappuccino - I'll have a cappuccino.

Il conto, per favore. The bill please.

“Quante”or “Quanto costa?” How much is it?

FACT: Italy consumes 220,000 tons of Gelati a year.

 Cono o coppetta? Cone or a tub?

Interesting toppings on La Pizza, Italy's favourite fast food.

melanzane aubergines
acciughe anchovies
capperi capers

The all important meats:

la carne	meat
il manzo	beef
il vitello	calf
il maiale	pork
la pecora	sheep
l'agnello	lamb
il pollo	chicken
il coniglio	rabbit
la gallina	hen

Oh, and most importantly! Questions to ask when you meet a sweaty armpit…

Quanti anni hai? How old are you?
Hai fratelli? Do you have brothers or sisters?
Hai bambini? Do you have children?
Che lavoro fa? What do you do for a living?
Lei è sposato? Are you married?
Lei è fidanzato? Are you engaged?
 

You know when to walk away when he says something like mia ragazza or fidanzata or donna. This means he’s talking about his girlfriend, sadly.

Common words

Dove Where
Molto very
ex. Molto grazie! Thank you very much

moglie wife

figlia daughter
figlio son
bambini children
piccolo small
più more
Olio oil
Aceto vinegar
A sinistra To the left
A destra To the right
Accanto all’albergo Next to the Hotel
Notti night
per stasera tonight

And lastly…

Andiamo, which means “Let’s go!”

Resources:

http://www.bbc.co.uk/languages/italian/talk/transcripts/
http://www.tantarobina.com/2008/3/23/pollo
http://italian.about.com/cs/pronunciation/ht/pronounceconson.htm