I'm wondering about the jars. How nice that they're so lightweight but when they heat up what about the the bad effects on food from heated plastic?
391778
Heated plastic in microwavable safe containers is currently under significant scrutiny these days. Although the "vote" is not in yet. Bisphenol-A, the chemical that supposedly leaches into food as a threshold is reached when plastic containers are heated to said threshold, is the chemical under scrutiny. Originally initiated when mothers were concerned for their babies when heating bottles of milk in microwaves; there is still NO definitive evidence that there is anything afoul occurring. Your safest approach would be less time in microwave or use the good 'ole stove.
391779
http://www.blendtec.com/blog/blendtec-introduces-new-bpa-free-blending-jar/
298213
Yes...I have put these in the microwave multiple times for no more than 1 min at a time and it has not done any damage to them. They don't get too hot and have not melted at all. I have heard that microwaving food in plastic is not safe because of chemicals that are released during the microwave process, but that is a seperat issue.
1935621
Just like anything plastic use caution when heating in a microwave. I have used them in the microwave many times. Again use caution as plastic weakens when heated and could melt if in too long.
424552
I have used quart jars many times in the canner and have never had this problem. I use only Ball or Kerr jars. If you are trying to use mayonnaise jars or some other kind of jar other than those specifically used to can, that may be the problem. I use the canner to heat the jars and also to can them in it. I've just made several juices in quart jars, canned pickled asparagus in quarts, etc. Have you been paying attention to when the book says to use the "grid" in the bottom and not use the grid? in the heating and canning process? It can also be caused by the jar being too cold when the hot stuff is put in it. Or, it can be cold stuff being put into a hot jar. Keep in mind that everything has to be either hot when it is being canned in the canner.
2059440
The jar is made out of thin plastic, although it might still break if dropped onto a hard surface, especially if you purchase the 5 lb container. The lids from my past couple of purchases seem to seal pretty tight so you shouldn't have to worry as much about evaporation.
1815106
If you didn't reseal the package in something air-tight ( like a jar) then they are probably bad. You can test if you fill a jar with something simple ( rice, beans, etc) and put one or more in, seal the jar, and see if the lid "pops" down via vacuum pressure- That would indicate the rest are still probably good. However, I also found with mine that a lot of them were not good from the get-go, even after keeping them in an airtight jar.
573260
this is a good point which I would like to know as I want to get one of these but not if an unhealthy chemical is leaching into the water from heating of the plastic. If anyone knows about this I would love to know. thanks
1609081
The handle, lid knob and feet on bottom are plastic ... I've had no problem with with too hot to handle or melting. The stoneware, glass lid and metal outside skin all get very hot on high, but we use weekly and have never had a bad burn. hope this helps some. John
1961312
The risk would be to the glass lids at higher temps. I have used them without incident up to 375 degrees.
1347754
I already replied however wanted to add that it is important not to over heat these heat packs You need to play around with the timing in each microwave., depending upon the wattage. If they are heated too much the contents will burn and smell like burnt popcorn (but not in a good way),
1206331
Good question, I haven't tested them in those conditions yet. However, because they are sealed foil pouches I would think they would do better than plastic bottles under those conditions. Heat is no friend to any perishable in car temperatures, but I would expect these would be better than nothing to have in your trunk JIC.
1885872
Mine has been microwaved a few times a fast for several months with no problem. I'm more careful with the lid though.
227133
100% safe. Here's a good place to start: http://www.nomiku.com/support/faq/is-it-safe-to-cook-in-plastic/
1928178
I've reheated mine when they were not completely cool, but I reduced the heating time in the microwave. A few years ago, I over heated one of mine (I put one in the microwave one early morning while I was bleary eyed.) I accidently hit 14 minutes instead of 7 or 8. When I came back in the kitchen, the outside plastic had melted allowing the inside liquid to leak out. It was gooey and stunk to high heaven. As long as you use the recommended heating times, and don't go overboard like I did, you will be fine. I've been using these for years with no problems, other than the one I caused.
1237118
I keep mine in canning jars -- you know, mason jars and the like. and those I keep in a dark cool place. With taht approach you can literally keep them for quite a few years. Personally, I'd avoid zip-loc's -- they're plastic and do drop volatiles, albeit at a very slow, non-dangerous rate, but even so -- and the jars even look cooler! :}
1471000
Haven't experienced any problems with heat. The containers are great for holding moisture. I haven't had to water my front porch plants as often since switching to these.
793322
I don't know what the manufacturer says, but I would not. Even if they said it was okay, I like it for its perfect use as a salad/cold cutup veggies use. Microwaving shortens the life of plastic in general and I recommend using either a Rubbermaid product or the Ziploc reusable but disposable containers for items that need microwaving. An added suggestion for microwave items is that my husband has me put such items in a plastic baggie (very cheap) then he has a large mug that he reheats food in. If you have that option, it's great because especially tomato products and enchilada sauce ruins plastic. I don't know what the manufacturer says, but I would not. Even if they said it was okay, I like it for its perfect use as a salad/cold cutup veggies use. Microwaving shortens the life of plastic in general and I recommend using either a Rubbermaid product or the Ziploc reusable but disposable containers for items that need microwaving. An added suggestion for microwave items is that my husband has me put such items in a plastic baggie (very cheap) then he has a large mug that he reheats food in. If you have that option, it's great because especially tomato products and enchilada sauce ruins... » Read More I don't know what the manufacturer says, but I would not. Even if they said it was okay, I like it for its perfect use as a salad/cold cutup veggies use. Microwaving shortens the life of plastic in general and I recommend using either a Rubbermaid product or the Ziploc reusable but disposable containers for items that need microwaving. An added suggestion for microwave items is that my husband has me put such items in a plastic baggie (very cheap) then he has a large mug that he reheats food in. If you have that option, it's great because especially tomato products and enchilada sauce ruins plastic. « Show Less