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Posted on Feb 11, 2008 in Bento, Equipment, Meat, Pasta or Noodles, Recipe, Review, Tips | 61 comments

Glass bento boxes & microwaving

Glass bento boxes & microwaving


A common concern with microwaving (or even packing) lunches in plastic containers is the potential of carcinogens or hormones from the plastic to leach into the food. I’m not here to lecture anyone on the relative danger or safety of plastics and the microwave, but I did come across some interesting material when reading up on the subject.

Some say not to worry: the FDA says microwaving in plastic is fine, Snopes says a viral e-mail about the dangers of microwaving or freezing in plastic is an urban legend, and the FSDA has info on cooking safely in the microwave. The Natural Scientist blog has a couple of interesting science-oriented entries on the safety of microwaving plastic wrap with respect to dioxins and phthalates. On the more conservative side, Green Living at Care2 has a clear list of good and bad plastics here; combine that with the chart of plastics symbols on Reusable Bags’ FAQ on lunch gear health and safety issues and you’ve got a way to identify what kinds of plastics you have in your home and act on your own conclusions. I’m coming up short on authoritative material about the dangers; if you know a reputable article or source please post the URL in comments. For lunch packers, I’ve written previously about metal bento boxes, but their downside is that they can’t go into the microwave. (Click to read the full post with a sample preschooler lunch…)

Tempered glass bento box (open)

No matter what your take-away on the plastics issue is, you may occasionally want to microwave your bento lunches, and one look at my nasty old Tupperware tells me that you can stain or damage plastic containers by microwaving foods high in fat, sugar or staining ingredients such as tomato or turmeric (stain-removing ideas here). Some plastic bento boxes are made of special stain-resistant materials, which helps with staining but not with other concerns.

Another solution is to use shallow tempered glass boxes, which are heavy but will not leach chemicals into the food inside or absorb food odors. They’re not ideal everyday containers for young children as they’re heavy and can break if dropped. They may be worth it, however, if you’re really concerned about the plastic issue or plan to do a lot of microwaving.


  • If you plan to microwave your lunch, pack only food to be warmed in the tempered glass container, and bring a separate side dish container with fresh fruits, cheeses, or anything else you want cold. That, or put cold food in a removable subcontainer that can be easily taken out before warming.
  • To avoid breakage, pack tempered glass boxes in insulated lunch bags with a bit of padding to cushion any unintentional falls. You may want to pull out your cloth napkin and practice those furoshiki ties to protect them further if you’re packing multiple glass containers in the same lunch bag.

Tempered glass bento box (closed)

There are a number of companies out there that sell tempered glass containers with secure, watertight lids similar to Lock & Lock’s, one of my favorite brands in food storage (U.S. online store here). These locking-type lids provide more security against spills than standard push-on lids (think Tupperware), which might come open if handled roughly in transit. Evidently a number of companies have been selling these kinds of containers under the “GlassLock” name (SnapWare, Sam Kwang, Lock & Lock, Wellbeing, etc.) and have been fighting it out in court, but they’re all similar in function.

REVIEW: I bought a 400ml (14oz.) Wellbeing GlassLock tempered glass box for US$4.50 from Kamei in San Francisco to test for Bug’s lunches (product #GL-03, see the SF Bay Area bento gear shopping guide for store details — Kukje also stocks these). Wellbeing has a line of tempered glass containers that come in sizes that can be used as bento boxes or side dish containers. I was pleased with the watertight lids, which are easy to open and close, and are better than the SnapWare lids I’ve tested out. Safe for the dishwasher and microwave, they’re pretty indestructible — just be sure to open the lid to vent when microwaving, and don’t put them in the oven. I’m tempted to get another size to store small amounts of leftover kimchi in the fridge without staining or smelling up my plastic containers. Their 710ml version (product #G-17) looks like the right size for an adult bento, and they have a number of approx. 150ml versions that would work fine as a side dish containers.

Sources: If you have a good Korean market or Asian housewares store near you, try there first to avoid shipping fees. An eBay search on “GlassLock” turns up a seller in Korea with a good selection and international shipping. U.S.-based has a number of GlassLock products in their Kitchenware section, and has several Snapware versions in 3-cup, 2.1-cup, and 1.7-cup sizes (use this handy conversion tool to figure out equivalent volume in ml). (EDIT: Ichiban Kan’s online store now stocks the Wellbeing GlassLock boxes; check back later if they’re out of stock. See my review of their online store for other bento-friendly links.) I have no commercial affiliations with these sellers.

* * * * *

Sausage & broccoli rabe pasta lunch for preschooler

Contents of preschooler bento lunch: Italian sausage and broccoli rabe with whole wheat pasta, roasted mushroom caps (recipe below), Moro blood orange slices, and cheese cubes. In a fit of healthiness, I picked up a huge package of whole wheat pasta from Costco, only to discover that I’m not a big fan of the texture…

Morning prep time: 12 minutes, using leftover pasta. In the morning I popped the mushroom caps in the convection toaster oven to roast while I microwaved the pasta to restore texture, and sliced the orange.

Cooking: To roast the mushroom caps, I lightly brushed the surface of the clean mushrooms with olive oil, and seasoned with salt and pepper. They cooked for 6-7 minutes in the toaster oven at 400 degrees F (375 deg. F in the convection toaster oven), then turned it upside down on a cooling rack to cool and drain the juices that accumulated during roasting. These are then ready for any number of fillings. In another lunch I filled them with a mixture of chevre, sauteed broccoli rabe and pancetta, garlic and a little butter, and ran them under the broiler in the toaster oven to brown. That filling got a thumbs down from three-year-old Bug, though, who likes his mushrooms plain.

Packing: I cut a longer plastic disposable food divider by a third to make it fit across the box. I stacked two roasted mushrooms on top of each other, and plugged the gap with cheese cubes to stabilize the lunch for transit. Bug’s preschool doesn’t warm the children’s bentos; if I were packing a lunch for the microwave I would want to either pack the oranges and cheese in a side dish container or put them in a removable subcontainer for easy removal before heating.

Verdict: Bug ate the cheese cubes and most of the pasta at preschool, but left the oranges and mushrooms until after school. He was enthusiastic about eating those in the car, though, and thanked me for not putting any filling in his mushrooms. I guess an old dog can learn new tricks! ;-)



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  1. Yum! And thanks for the info on the glass containers. I may look around for those just for storing leftovers.

    Don’t give up on whole wheat pasta too quickly. There are some brands I love and some I hate. It took a while to find one I really love all the time. Gia Russo is my favorite - nutty and flavorful, but not gummy and weird hard/soft at the the same time. I also found that shapes are better than long pastas. Strange, but true.

    Good luck, and keep up the great posting!

  2. I’ve been experimenting with whole wheat pasta myself. The texture does take some getting used to, but it’s particularly good with a tomato based sauce. I tend to use less of it than I would with regular pasta, and then I go extra heavy on the veggies.

  3. I’ve got a 600 ml square glasslock and love it.
    For SF South Bay locals: I got mine at Marina Supermarket in Cupertino and they have a variety of sizes. Mine was $5. I’ve also seen them at Walmart for more ($8 for the same size).

  4. What about pyrex storage dishes instead of purpose-made bento gear? I love mine for leftovers, and the lids are secure enough for the travel I’ve done with them. I’m sure they’d work well in a bento bag.

  5. Happy Chinese New Year!

  6. I tried several brands of whole wheat pasta and found huge differences in taste. The hands down best is Bionaturae, sold in Whole Foods (among other places-that’s where I get it). It’s SO much better than brands I have tried from Trader Joes and Costco. Two points: cook it a little longer than directed, and cook in well-salted water. Al dente is NOT what you are after.

  7. Personally, I dream of owning one of those traditional wooden/bamboo (not sure which they are) bento boxes. Do you have any experience with those? Although, they’re probably not suitable for young children to use…

  8. A recent statement made of one of the morning programs was that it is being recommended that we should not reheat any of our foods in plastic. I think, in the end, it is up to the consumer, what chances we are willing to take. According to the Japanese lady at the Japanese store, many of the dangerous chemicals used in some contries for stabalizers in plastics are not used in Japan manufacturing.

    My family uses a mix to of glass and plastic, but we are using less plastics than ever before.

  9. I switched to using glass containers to store leftovers.I bought the corning ware variety you find at walmart for less than 54 each.They have a plastic lid and work great for leftover. I used to use plastic containers all the time and microwave in it,but the stained containers and the fact that its plastic got to me.

  10. oh btw here are some glass containers i foudn at container store

  11. Thanks for the info on glass containers. Between worries that I’ll stain/damage my pretty (and hard to get) bento boxes and worries about microwaving in plastic, I’ve been eating cold lunches or packing my hot food in silicone cups. A glass box might be just what I need.

    About the whole wheat pasta - I also want to say “don’t give up!” I didn’t switch brands (there’s only one kind easily available here) but I did discover that it takes a lot more cooking than regular pasta to get a good texture. Once I cooked it longer (and I think it was a lot longer- nearly ten minutes), it had nearly the same texture as my regular stuff.

  12. I agree on the “don’t give up” - I’m sure you know the health benefits. I LOVE wheat pasta, all of it. It has so much more flavor than your ordinary noodles.
    Have you ever tried those Yam noodles sold in water packs? They’re called Shirataki, I think? They say they have little calories, no fat….but many sites say they smell so I’m fearful of them.

  13. Thanks for all of the information on this post, as well as your blog in general, it’s a great read and v. informative as well!

    I noticed you had mentioned the Lock & Lock brand on here quite a few times, and then came across a 20-piece set at Linens n Things for 29.99. I’m really excited to use it for my kitchen and for my work lunches!

  14. I want to chime in with the whole wheat pasta. It’s all we buy and having just started packing bentos last week, I’ve found it takes a special knack to cook it right and then cool it immediately so the texture is good to eat cold. I mixed some last night in a sauce pan with sauteed onions and yellow squash with a splash of red wine vinegar and packed it cold today. It was really good.

  15. Thank you so much for the link to the Lock&Lock site - they are by far my favorite containers for almost everything. I never managed to find the U.S. online store though, so Thank You!!!

    Really - our whole kitchen (and a good chunk of our apartment & pet food) is pretty much packed in lock&lock and we use them for our lunches everyday - they hold up really well, even to being abused and banged around.

  16. This Pyrex container is divided but a tad shallow and may work for some items.

  17. Thank you so much for posting this. I don’t microwave plastic so I transfer from my bento to a glass bowl. I’m going to look for those. About the whole wheat pasta- Eden Organics makes GREAT udon noodles they aren’t as “cylinder” as most udon noodles but they are yummy!

  18. Here is an article on microwaving by Dr Mercola:

  19. And the 2nd part:

  20. + 1 on the whole wheat noodles. My Man, who is a notorious hater of all kinds of noodles will lick the plate clean if I make them with Pistachio and Basil Pesto. Ever since, I have found that whole wheat noodles go better with sauces with a lot of personality, so that the sauce does not overpower the base.

    love your site, btw.

  21. @1 from Jessica: Yes, I’m thinking that’s what I’ll probably use this box for — leftovers. It’s a little heavy for Bug and at 400ml, too small for me. But it looks perfect for storing/microwaving leftovers, and if I’m ever packing a microwave lunch for Bug I’ll pull it out again.

    Thanks for the advice and encouragement on the wheat pasta — because of all the feedback here I won’t give up on it yet!

  22. @2 from Miriam: When you say you use less of it than with regular pasta, do you mean less sauce or less pasta? I’ll try again…

  23. @3 from freecia: Thanks for the South Bay Glasslock source, freecia!

  24. @4 from eudyptes: No reason Pyrex wouldn’t work, but I really prefer the stability of the locking lids — that’s why I left Pyrex out. If you’re careful with your bento in transit, though, Pyrex would be a fine alternative.

  25. @5 from Cindy: Gung hay fat choy!!!

  26. @6 from Arb: Thanks for the Bionaturae recommendation and whole wheat pasta cooking tips, Arb — I’ll play around with what I’ve got and keep an eye out for your brand…

  27. @7 from Miyuki Mouse: I haven’t actually used the wooden or bamboo boxes at home, although they’re definitely beautiful and photograph nicely. One of these days I’ll pony up for one, it’s just harder to justify as I don’t really need it and the upkeep is more demanding than the dishwasher…

  28. @8 from Jen: I agree that we all need to determine our own comfort level with plastics and microwave — I’m not interested in ranting about it one way or the other.

  29. @9 from sowhatsnewtoday: Great tip on the cheap Corningware at Walmart! What do you think of the security of the lids? That’s my main hesitation there…

  30. @11 from R. M. Koske: Thanks for the tips on the whole wheat pasta, RM — I’ll bear them in mind as I experiment with it some more. With all of this feedback and encouragement, I’m now determined to perfect my technique!

  31. @12 from Monica: I use shirataki noodles (and Malony noodles) in Japanese nabe hotpot dishes because you can simmer the heck out of them and they don’t fall apart. They also take on the flavor of the broth you cook them in, so I haven’t noticed any smell issue (but then again I’m not eating them plain or sauced like pasta).

  32. @13 from mom2twins: I just spent some time poking around the Pottery Barn site, but couldn’t find those glass containers you’re talking about. Would you happen to have a link we could check out? I did find their lunch bags, though, which look attractive.

  33. Re: the pasta question . . . use less pasta, more veggies. Chunky tomato sauce or grape tomatoes and garlic do well with it.

  34. @14 from K: Wow, great tip on the cheap Lock & Lock set at Linens & Things! Thank you for the heads up! I’m looking to replace my decrepit Tupperware soon at my husband’s request, and Lock & Lock is definitely on the agenda. I may go for their Premium line (stain-resistant), a stackable L&L, or the Glasslock. Haven’t decided yet…

  35. @15 from vampyra1: Good sourcing tip on Kmart, vampyra! I’ve got a number of different bags for Bug’s lunches. He doesn’t do well with furoshiki as he complains they’re too hard to untie/open, so for now I’m sticking with drawstring kinchaku lunchbags (Cars & Anpanman) and zippered insulated lunchbags (Shinkansen, Lock & Lock bag, and the navy blue rabbit bag from his thermal bento set). Photos are in my Lunch Tools set on Flickr.

  36. @16 from Jody: What’s your technique to cooling the whole wheat pasta so it’s good to eat cold? A rinse with cold water?

  37. @17 from Shana: I stumbled on the Lock & Lock online store the other day when I was trying to figure out the whole “Glasslock” conundrum — I can’t believe they haven’t linked it more prominently from their main site! Like you, I’m a L&L convert & fan because of the amount of abuse it takes — the lids do great in the dishwasher, no warping. :-) I’m going to be replacing the nasty old Tupperware in our kitchen soon, and the only question for me is which line of Lock & Lock to buy…

  38. @18 from rainee: Hmm, the divided Pyrex container is 5.5 cups, not 2 — that’s 1320ml (SO BIG!!). Was there a divided 2-cup container? If anyone’s tried these out, I’d love to hear feedback on the security of the lids…

  39. @19 from Kelley: I think I tried the Eden Organics buckwheat noodles back in our nine-month gluten-free phase in 2005 as they had some without wheat flour. Took a little getting used to, but we were happy to be eating somewhat normal noodles despite the (mistaken) celiac disease diagnosis.

  40. @35 from Miriam: Ah, thanks for the answer. I’ll try that out then.

  41. @20/21 from Saffron: Thanks for the links on the dangers of microwaving food, Saffron!

  42. @22 from sweetie: Thanks for the saucing tips for whole wheat pasta, sweetie! Time to experiment with cooking techniques and sauce combinations…

  43. Reply to 38:

    I know it’s horrible for your fridge as far as keeping the tempature consistent, etc. But what I did was cook the wheat pasta just slightly less than it called for (which is longer than ‘normal’ pasta’) Put it in a strainer and then stuck it in the fridge while it was still steamin- yikes, I know. BUT- I found that it keeps it texture and looses some of the ‘squishy-ness’ I think most people don’t like with whole wheat. Once it was cooled enough to touch but still warmish, I bagged in individual serving sizes making sure the seal on the ziplock was tight and all air was out, then put the bags in a freezer container and into the freezer they went. Then, I just pull out a bag when I’m packing. I usually just let it defrost on its own while I’m doing the rest of the prep- it really doesn’t take much at all since I just freeze pasta by itself. Once it’s thawed, I toss it with whatever I want- veggies, light sauce, cheese, etc.

    Much longer comment then I meant it to be- sorry.

    Oh, and I’d echo the part on using shaped pasta over spagetti or other straight ones. I use rottini. It holds the good texture much better. Plus, it holds the light ‘sauces’ I use better- red wine vinegar, lime or lemon juice, italian dressing.

  44. Yet another whole wheat fan here, though my opinions are probably redundant by this point. I think I also agree that shaped pasta is best-I am addicted to whole wheat rotini, the brand escapes me at the moment but mmmm. Love that nutty flavor.

    Also, just wanted to say those mushrooms look fantastic. I’ll have to try that next time we go shopping..

  45. Biggie, There was a two cup one that Amazon had a while ago. I can’t find it anymore on Amazon and have never seen in in the local store but Ebay has it. I use the regular undivided containers that I can find at my local Target/Walmart and they work well for rice and such but are leaky for liquids. Here are links to both.

    Pyrex Rectangular Dish on Amazon
    2-cup divided Pyrex dish with lid on eBay

  46. @45 from Miyuki Mouse: Interesting on mixing whole wheat and regular pastas. I guess you’d have to cook them separately, though, because of different cook times?

  47. @47 from Rachel: I’ll keep an eye out for the whole wheat rotini, thanks!

  48. @48 from rainee: Thanks for the links, rainee.

  49. You can also get these pretty cheap in a small home store in Oakland in the Pusan Plaza.

  50. @53 from tc: Thanks for the Oakland shopping tip, tc!

  51. Thanks for the L&L at Linens & Things tip. I bought a set last weekend - even better if you can find a 20% off coupon!

    Question on the divided Lock and Lock’s (like the one in Biggie’s lunch set): do the dividers extend all the way to the top? Any leakage across compartments?

  52. @56 from Owen’s mom: The dividers on the divided Lock & Lock containers come all the way to the top, but they’re not 100% watertight. Enough to handle moist dishes shaken around, but not for a soup or liquid.

  53. Thanks for highlighting these great items. All you wrote above essentially matches the reason we decided to carry them.

    Keep up the great work.

  54. For those looking for these containers at a reasonable price, my wife bought a 9 container pack of the Glasslock brand at Costco on the cheap.

  55. @62 from ctyankee: I’ve seen the plastic Snaplock containers at Costco before, but never Glasslock. I wonder when they started stocking the glass ones?

  56. Can I just say I love you and what you’re doing!! The wealth of info you put up here is so great. I am just starting to consider bentos for my daughter. She goes to preschool 3 days a week. I know she would love one of those cute hello kitty lunch boxes. But I am afraid of where they are manufactured and what they may contain. This is perfect


  57. There has been a lot of research on BPA in the scientific literature but most of this hasn’t shown up on the web. Wikipedia actually has a good selection of recent research.

  58. I have found the GlassLock containers at TJMaxx and Marshall’s for 1/2 the regular price. I also picked one up on clearance there. If anyone lives near these stores, it would be worth checking out.

  59. Anyone know if GlassLock is made from Soda lime or borosilicate glass?

  60. Thanks for asking that Tracey. We carry them, and I didn’t know the answer. So we called and found out.

    They are made from soda lime.

  61. Hi, I am trying to find where I can buy replacement lids for the Wellbeing Glasslock containers. Does anyone know where I can purchase them.