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How does plastic wrap work, and why does it cling to some surfaces well but not others?
The ideal plastic wrap adheres to all sorts of containers, including glass, metal, and hard plastic. The trick for manufacturers is to engineer the plastic so that it attaches well to what the consumer wants it to attach to.
Clair Hicks, professor of food science at the University of Kentucky, says that “back in the late ’80s and ’90s plastic wrap was so clingy that you first had to work hard to find the edge on the roll. Then when you successfully ripped off a piece it would immediately fold back on itself, so it was really hard to work with.” Eventually, consumers dictated the evolution of plastic wraps, using their dollars to purchase those that had less aggressive cling, and manufacturers developed formulas that made their products easier to handle.
Plastic wraps are generally made from a vinyl or polyvinylchloride molecular configuration, which gives the material its “clingy” characteristic. Plasticizers add stretchiness. The level of clinginess depends on a mix of factors, for example the electrical charge the wrap carries, plus the charge the container carries.
“Glass, as well as some plastics, has a net negative charge on its surface, so a wrap that has an opposite charge is going to cling quite well to these surfaces,” says Hicks, though of course it’s unlikely that you would know what charge your container carries. A plastic wrap that carries the same charge as the container will not adhere as well.
Plastic films can also be hydrophobic (meaning they repel water) or hydrophilic (they attract water). Hydrophobic wrap is better at stretching across the tops of bowls and wrapping deli meats.
Hicks thinks that Saran wrap is your best bet for cling. It’s also one of the most expensive brands on the market, probably in large part due to the barrier film included in its formula, according to Hicks. Barrier film keeps the smells from leaking out of a wrapped product.
CHOW’s Nagging Question column appears every Friday.
yes i get the idea that opposite changes will cling but why does it cling to itself?
For those who really like PVC wrap, there is something to read about from The Green Guide (owned by National Geographic). Not all plastic are created the same and PVC is one plastic that may affect your health.
PVC Cling Wrap: Too Close for Comfort
by Pamela Lundquist
http://www.thegreenguide.com/doc/88-89/lundquist2
The Reynolds 200ft, Costco 3000ft, Stretch-Tite 500ft are made of PVC...+READ
For those who really like PVC wrap, there is something to read about from The Green Guide (owned by National Geographic). Not all plastic are created the same and PVC is one plastic that may affect your health.
PVC Cling Wrap: Too Close for Comfort
by Pamela Lundquist
http://www.thegreenguide.com/doc/88-89/lundquist2
The Reynolds 200ft, Costco 3000ft, Stretch-Tite 500ft are made of PVC with plasticizer.
Commercial kitchen has a very high turn over rate on their meat consumption. The PVC wrap may just warp a piece of meat for an hour or two before it will be cook and consumed. The supermarket wrap a meat for display and expect to sell it within a day.
In household kitchen, consumer may wrap a piece of meat for days (or weeks) of storage. This longer storage time allows a higher amount of chemicala being transfered into the meat, that eventually be consumed by human.
Almost all Food Storage Bags, under all brands names, are made of LDPE. No Food Storage Bag, Cup, Plate, Bowl of any brand that I can recall, are made of PVC.-COLLAPSE
Good Sense 200ft retailed at $1.60 at Biglots works great. It has the right balance of cling and tensile strength. That translate into 0.8 cent/ft.
Harris Teeters, CVP and Food Hold also offers a great house brand plastic wrap at a competitive price.
The film cling water tight with glass and ceramic. All you need to do is stretch the film out a little (less than an inch) and apply to the glass...+READ
Good Sense 200ft retailed at $1.60 at Biglots works great. It has the right balance of cling and tensile strength. That translate into 0.8 cent/ft.
Harris Teeters, CVP and Food Hold also offers a great house brand plastic wrap at a competitive price.
The film cling water tight with glass and ceramic. All you need to do is stretch the film out a little (less than an inch) and apply to the glass surface. The counter elastic movement will seal the glass bowl and not even a drop of water will lead out. These PE cling film are so much more elastic than the tradition brands like Saran wrap.
You will also notice the high transparency on the film. Very beautiful.-COLLAPSE
Side note -- can I just lament the almost complete disappearance of a perfectly good word -- namely "tenacity" -- which has been supplanted by the clumsy term "stick-to-it-ive-ness."
UGH!
Stretch-Tite is the way to go. My husband was always a Saran Wrap, but after working in the food industry, I wanted to find something that was close to the commercial grade plastic wrap. Stretch-Tite is the best-- it's a bit stretchier, sticks to everything, and has the best dispenser.
Press-n-seal is GLAD's domestic answer for Parafilm. (I'm currently a chemist and I love Parafilm.) Parafilm...+READ
Stretch-Tite is the way to go. My husband was always a Saran Wrap, but after working in the food industry, I wanted to find something that was close to the commercial grade plastic wrap. Stretch-Tite is the best-- it's a bit stretchier, sticks to everything, and has the best dispenser.
Press-n-seal is GLAD's domestic answer for Parafilm. (I'm currently a chemist and I love Parafilm.) Parafilm sticks to anything once stretched over it, but it's prohibitively expensive. I think it's because of its thickness and the way it has to be packaged: there must be a separate wax paper placed in between the sheets because of its self-adhesion qualities. And because it's more difficult to dispense, cut, and separate from it's paper, I find it a lesser material to use for food. Stretch-tite is by far the winner, the company also makes commercial grade plastic wrap.
Strangely enough, Stretch-tite is really affordable compared to Saran Wrap and the Press-n-Seal material. At 1.5 ct/ft, it's a lot cheaper than Saran Wrap at 2.7ct/ft or Press-N-Seal at 5.2ct/ft. It's awesome on every level.-COLLAPSE
I am in the industry of making LDPE plastic wrap. So I know a thing or two about it. However I am not a chemisty major nor speaking on behalf of my company. I am just sharing with you what I learn from my job. Please do not hold me with any legal liability.
There are two kind of plastic wrap, PVC (yellowish) and LDPE (natural transparent color). There is no regulations in US that plastic wrap...+READ
I am in the industry of making LDPE plastic wrap. So I know a thing or two about it. However I am not a chemisty major nor speaking on behalf of my company. I am just sharing with you what I learn from my job. Please do not hold me with any legal liability.
There are two kind of plastic wrap, PVC (yellowish) and LDPE (natural transparent color). There is no regulations in US that plastic wrap suppliers need to inform consumer if the product is made of PVC or LDPE. However some countries already have restrictions on using PVC to make drinking bottle or infant toys as to avoid chemical migrate into human body. The chemical attack may affect our reproductive organ, apply to both male and female. Because of body size by weight, the affect will be more significant on small children than adults.
Let's start:
The good thing about PVC wrap is the physical properties. It is very elastic and it cling well with glass, ceramic, stainless steel. Reynolds, Kirland, Stretchtite are all PVC.
There is one catch. PVC material has to mix with a plasticizer to create such a cling and elastic property. This plasticizer will always migrate into the meat with fat content, such as salmon, beef, chicken leg, pasta and cheese. The chemical migration rate may speed up when reheating inside microwave.
You may want to read more about PVC plastic wrap under www.thegreenguide.com or just Google PVC plastic wrap. TheGreenGuide is owned by National Geographic, has a suggesting shopping list, in which, it suggests to avoid PVC plastic wrap. In addition, PVC is probably one of the worst plastic when it comes down to environmental impacts. You will get toxic gas during heating or burning PVC and it is very hard to recycle any PVC products.
I heard (once again could be wrong) some company such as Wal-mart has a time table that all products sold there, should be PVC free by a certain date.
It is still hard to proof how much plasticizer you have to consume daily before it causes you cancer on your reproductive organ. But why take the risk when you don't have to. Nobody can denial this chemical mirgration from PVC plastic wrap. The supplier can only argue you would not be consuming enough to give you cancer. So they said it is safe to use it, assuming you know how to use it probably and correctly.
Look closely the warning at the back of the Kirland 2,000ft PVC plastic wrap. I recall I have seen (one time) the box said in small font that user should leave an inch of space between the plastic wrap and fatty food but the warning did not explain why. I don't know if the warning is still there so please check yourself.
Next time if you visit a Japanese supermarket, you may check their sushi tray on the shelf. The sushi are being wrapped by PVC plastic wrap, but the staff will make sure the fatty fish is sitting on the tray while there is some space between the fish and the PVC wrap. No direct contact is allowed between the fatty fish and the PVC wrap.
About Saran wrap, if you love this brand you may notice that SC Johnson has changed the formular from PVC to LDPE a few years ago. Goto Saran Wrap website and see. They used to have a full page explaination telling consumer why they move into LDPE. The article is very cleverly done and I beleive it is written by their corporate lawyer. Once again, you can imagine why the major brand leader switch out of PVC.
Back to LDPE plastic wrap. The advantage is NO CHEMICAL migration and the material is the safe choice. Unlike PVC plastic wrap that mix PVC with plasticizer (about 30% or more), LDPE plastic wrap is +99% pure LDPE.
LDPE is just pure Carbon and Hydrogen molecules. It is clean to make and easy to dispose. You only get Carbon Dioxide and Water when heating up or burning LDPE. All the food storage bags are made of LDPE for a good reason. LDPE is also a strong barrier of mositure so your meat won't dry out in the fridge.
The catch is, controlling cling is a very difficult process with LDPE. Factory usually can either make it overly cling or not enough cling. It is because they are using a similar process that make pallet wrap, the film that wrap around cargo and stop it from falling during transportation. This pallet wrap process emphasis on self cling, the cling between plastic film to another layer of plastic film. That is all this cling additive does.
The target property of a household LDPE plastic wrap are as follow:
- Control cling. Very strong cling with glass and ceramic but no cling on plastic (itself). This way, the cling film is very easy to dispense. For the cling, it ris equired to be strong enough to hold water in a testing baker and shake +40 times up-side-down with no water leaking.
- High clarity. This give consumer a general sense of hygenic feeling. There is an ASTM testing procedure and require cling film to be at least +90% light transparency.
- High tensile strength. This mean the film itself is strong and it can't be tear aparted by average household's hand. With such a strong cling with glass, if the bowl turned side-way, you want the cling wrap to hold the chicken inside the bowl. At the same time, the plastic film is required to be elastic as the meat is a 3-dimensional surface.
- Easy cutting. This could be tricky but is a critcal factor on user experience. The catch is designing a non-aggressive cutter that can cut the film very well yet it won't cut any fingers. Please remember the plastic wrap is high in tensile strength, that is designed for strong hold.
As demanding as it sound, such a LDPE plastic wrap does exist. It is not a miracle product but at least make the user experience much more friendly and enjoyable.-COLLAPSE
"Please let me know if any household wrap works as well, as Parafilm is expensive."
See post Number One in this thread.
http://www.cooksillustrated.com/testing.asp?testingid=222&bdc=2664&extcode=L7JN4BL00
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Parafilm M. It's used widely within laboratories, but rare outside (it's used by some hobbyists and gardeners). I purchase mine from science supply vendors. It is a wax-like film, stretches easily and seals incredibly well.
Take a glass, fill it halfway with water, stretch a piece of Parafilm over the mouth and press around the edges to seal. Turn the glass upside down and shake it with...+READ
Parafilm M. It's used widely within laboratories, but rare outside (it's used by some hobbyists and gardeners). I purchase mine from science supply vendors. It is a wax-like film, stretches easily and seals incredibly well.
Take a glass, fill it halfway with water, stretch a piece of Parafilm over the mouth and press around the edges to seal. Turn the glass upside down and shake it with moderate force for a minute. It won't leak, though the parafilm may stretch a bit. Please let me know if any household wrap works as well, as Parafilm is expensive.-COLLAPSE
I also have a drawer set aside for just wrap. The press and seal is the best IMHO, but then I haven't used the commercial plastic wrap, just the cheapo glad wrap-now I understand why it doesn't work!!
I've become a big fan of the press and seal wrap. I have several Costco sized rolls of genuine Saran Wrap taking up space in my wrap drawer (why, yes, I do have a whole drawer for wrap) but I don't imagine they'll ever get used.
i cannot tolerate using any supermarket plastic wrap after using the professional stuff. if you can pick up a box (usually 2000 ft) of culinary film from a restaurant supply, get it! it'll last you a year and is *hugely* superior to any store brand. the box is a little bulky in a home kitchen and you'll want to watch the wicked edge if you have kids in the household, but there are tradeoffs to...+READ
i cannot tolerate using any supermarket plastic wrap after using the professional stuff. if you can pick up a box (usually 2000 ft) of culinary film from a restaurant supply, get it! it'll last you a year and is *hugely* superior to any store brand. the box is a little bulky in a home kitchen and you'll want to watch the wicked edge if you have kids in the household, but there are tradeoffs to everything. i always feel badly for the top chef contestants wrestling with the crappy glad film-- they always have big bunches at the edges of whatever they are wrapping, because they are used to the real stuff. nimma even blamed her failed flan on the glad film, and the comment made it through editing.-COLLAPSE
Joe Blowe beat me to it--give me Stretch-Tite or give me death.
I loved the Reynolds EZ Slide (with the cutter) and wrote a few lines about it back in 2006.
Here is the link http://www.sergetheconcierge.com/2006/02/reynolds_plasti.html
I get comments almost daily lamenting the fact that it was discontinued.
Will mention your story on 'Serge the Concierge'
Bon Week-end
Serge
If you keep the plastic wrap roll in the fridge, it won't fight you getting a piece off. No idea why, but it works. I use Saran, don't know if it's different with other brands.
I think Stretch-Tite puts Saran-brand wrap to shame...
http://www.stretchtite.com/
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