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5 ounce thermos
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Daniel Collins
(Diablo-V) - M

Locale: Orlando FL
5 ounce thermos on 09/21/2013 00:06:51 MDT Print View

I saw a thermos for food slow cooking made from a used peanut butter plastic jar wrapped with reflectix.
As far as I know those jars are made from Polycarbonate. (Edit: They are PET plastic)
Mine will be made from 1/2 inch walmart blue sleeping pad around the jar, which is where I got the 5 ounces weight.
I love the taste of thermos cooked cereals and grains, but before I waste my time - does anyone know whether the Polycarbonate is safe with boiling liquids from the toxicity aspect ?

Edited by Diablo-V on 09/21/2013 21:50:39 MDT.

John S.
(jshann) - F
Re: 5 ounce thermos on 09/21/2013 06:16:03 MDT Print View

"Plastic #1: This is polyethylene terephtalate, also known as PETE or PET. Most disposable soda and water bottles are made of #1 plastic, and it’s usually clear. This plastic is considered generally safe. However, it is known to have a porous surface that allows bacteria and flavor to accumulate, so it is best not to keep reusing these bottles as makeshift containers. This plastic is picked up by most curbside recycling programs."

Edited by jshann on 09/21/2013 11:48:37 MDT.

Daniel Collins
(Diablo-V) - M

Locale: Orlando FL
PET Plastic on 09/21/2013 07:23:13 MDT Print View

Thank you john.
I guess only the big 5 gallon water jugs are Polycarbonate, not these.
I did some reading after reading your post and found, among other things, that the first plastic (PET) drink bottle was patented by the brother of a famous American painter:

"The first PET bottle was patented years later in 1973. At that time, Nathaniel Wyeth created the first official PET bottle under this patent. Wyeth was the brother of a well-known American painter named Andrew Wyeth."

Those clear plastic microwave meal trays are made from it and it is generally considered safe although indeed it can leach out chemicals if re-used.
Most disturbing is a warning about re-using those water bottles for, say, backpacking water containers:

"Recent studies have shown that reusing bottles made of PET can in fact be dangerous. PET was found to break down over time and leach into the beverage when the bottles were reused. The toxin DEHA also appeared in the water sample from reused water bottles. DEHA has been shown to cause liver problems, other possible reproductive difficulties, and is suspected to cause cancer in humans. Therefore, it's best to recycle these bottles without reusing them." (edit: this could also be urban legend rather than science. See comments further down in the thread.)

I also found out that Mylar is PETE plastic.

Edited by Diablo-V on 09/21/2013 21:52:48 MDT.

Colin Krusor
(ckrusor) - M

Locale: Northwest US
Polypropylene on 09/21/2013 10:32:00 MDT Print View

Daniel, have you considered a polypropylene container? Polypropylene is lighter and more impact resistant than the PET family of plastics, and polypropylene is very inert. It doesn't leach anything, no matter how many times you use it. Also, I know from first-hand experience that putting boiling water into a PET peanut butter jar will cause it to slowly shrink and deform. Polypropylene, in contrast, is unaffected by boiling water temperatures.

Just search on google or ebay for "polypropylene wide mouth bottle" or "polypropylene wide mouth jar". You'll find a range of prices from reasonable to outlandish, and some suppliers will only sell them in boxes of 6 or 12, but I would expect to find one for under $15 with some searching. There are many varieties, but the kind I had in mind look like this:


Jesse Reeves
(JesseR.) - M

Locale: Reno, NV
Ziploc on 09/21/2013 12:10:22 MDT Print View

I like the idea of a reusable insulated "thermos" to cook things in over the freezer bag insulated sleeve type thing. I wonder if you could find a size of ziploc bag that would sit inside the thermos to line it so that you wouldn't have to wash the thermos out after each use?
My initial thought is that the Ziploc round food storage containers with screw top lids would be a perfect start for your system... They're light, food safe, and cheap. Also available in a few sizes.
Ziploc Storage Containers

Colin Krusor
(ckrusor) - M

Locale: Northwest US
Ziploc Twist n Loc on 09/21/2013 14:20:08 MDT Print View

I think Jesse's suggestion is a good one. I took one of those Ziploc Twist n Loc containers on a two week trip on the California coast and it worked beautifully. The lid seal isn't quite water tight, but almost, and it will hold boiling water without deforming. They are made of polyethylene, which, like polypropylene, is very inert and won't leach anything. Those will be much cheaper and easier to find than a polypropylene wide-mouth jar.

Daniel Collins
(Diablo-V) - M

Locale: Orlando FL
refinement on 09/21/2013 14:29:51 MDT Print View

I like the polypro idea but what am I gonna do with that jar of skippy now ?

I HATE that stuff, just bought it for the jar.
I will start looking for a 28 oz polypro jar. I think aluminum would work too, but have not seen a wide mouth version yet.

I use those HDPE "Glad"and "Ziplock" screw top containers around the house, have been doing so for years. They have a bad habit of absorbing food odors, stains, due to the nature of the type of plastic. But then again it's just for backpacking so perhaps it might work. I will have to check up on any drawbacks as far as heat soaking the plastic is concerned.

My intent with this pursuit is to thermos cook my breakfasts - fresh grains such as oats and millet taste so much better when they are cooked this way. The plan would be to boil my water at dinner time, dump a pre-measured grain concoction into the thermos along with whatever dried fruits are in the mix, pour the boiling water in, cap it and shake it once, then wake up to a great warm breakfast. Having the plastic leech chemicals or aftertaste would definitely spoil the experience.

David Thomas
(DavidinKenai) - MLife

Locale: North Woods. Far North.
Plastics on 09/21/2013 15:11:09 MDT Print View

>"I guess only the big 5 gallon water jugs are Polycarbonate"

Most plastic 5-gallon water and all fuel containers I see are high-density polyethylene (HDPE). HDPE is very chemically resistant and takes extremes of temperatures, way past boiling, down below -40F (I could check, but I've personally used HDPE to those limits).

When I put plastic peanut-butter containers in the dishwasher, they get soft and warped. I would NOT plan to put boiling water in them.

James Couch

Locale: Cascade Mountains
Polycarbonate on 09/21/2013 16:16:48 MDT Print View

It would depend on the particular polycarbonate. Polycarbonate is a particular class of plastics and involves many formulas. The Nalgene bottles that were blamed for the original BPA scare were manufactured from polycarbonate plastic.

Doug I.
(idester) - MLife

Locale: PNW
Re: refinement on 09/21/2013 16:29:49 MDT Print View

"I HATE that stuff, just bought it for the jar."

If you haven't opened it, give it to your local food bank.

Christopher *

Locale: US East Coast
Re: PET Plastic on 09/21/2013 18:23:11 MDT Print View

"Recent studies have shown that reusing bottles made of PET can in fact be dangerous. PET was found to break down over time and leach into the beverage when the bottles were reused. The toxin DEHA also appeared in the water sample from reused water bottles. DEHA has been shown to cause liver problems, other possible reproductive difficulties, and is suspected to cause cancer in humans. Therefore, it's best to recycle these bottles without reusing them."

I have been looking into my use of plastics in the outdoors recently, including a few inquiries here on BPL. I am NO EXPERT and I am still pretty fuzzy on what exactly is fact vs. fiction in the plastic-is-poison debate, but ... and please I'm not looking to start a flame war ... I am fairly certain the above statement is unsubstantiated.

Apparently it stems from a student masters thesis paper that was not subjected to peer review, but ran through the media as a "scare-of-the-week". You will find that EXACT verbiage copied and repeated a thousand times in a thousand places across the web, dating back past 2011.

The hazards of a Wiki-world.

Edited by cfrey.0 on 09/21/2013 18:26:48 MDT.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: PET Plastic on 09/21/2013 18:34:02 MDT Print View

I use re-used PET water bottles

After a year or so they get cloudy or cracked so I replace them

I wonder if they leach chemicals

I backpack a fairly small percent of the time so probably doesn't matter

Colin Krusor
(ckrusor) - M

Locale: Northwest US
Insulation on 09/21/2013 19:03:16 MDT Print View

Daniel, Do you plan to keep the reflectix-wrapped container bundled up in a jacket overnight? I would be very surprised if a water filled container that size was still warm in the morning with only reflectix for insulation.

David Scheidt
(dscheidt) - F
Re: Re: refinement on 09/21/2013 19:55:10 MDT Print View

If you have opened the jar, use it for bating mouse traps....

Daniel Collins
(Diablo-V) - M

Locale: Orlando FL
clarification on 09/21/2013 21:49:28 MDT Print View

Clarifications, corrections,answers, responses - in no particular order:

The Polycarbonate large 5 gal I was referring to are those water dispenser clear blue jugs.

Correction: Gladware etc containers are not HDPE as I stated earlier, They are indeed Polypropylene. That'll teach me to not try to ID a plastic by its resemblance to a 6 pack band ... which is LDPE or plain old polyethylene. I have always grouped all things that feel like a ziplock or garbage bag or roto-molded kayaks into one thing and called it Polyethylene. I was wrong and from hereon a changed man. I will from now on refer to them all as "those things that no glue on earth will stick to".

My thermos - if I can settle on a material for its' reservoir - will NOT be wrapped with reflectrix. I saw one made with reflectrix that a guy used for camping which gave me the idea to make my own. As stated earlier mine will use 1/2 inch blue foam from Walmart sleeping mat material. As far as I'm concerned Reflectrix is just fancy bubble wrap and I don't think the foil (reflective) component therein has any benefit where liquids are concerned, but I'm open to someone showing me that it does if there's science behind it.
The blue foam will give me a solid insulator. It will be wrapped in Mylar packing tape on the outside as an outer barrier. If I could wrap it (outer layer)in 3 mil neoprene I would, but then the weight creeps up to well beyond 5 ounces.

On the PET water bottle scare- whether true or not I will not abandon my Smartwater 1 litre bottles for backpacking. They are just way too nice compared to drinking from a floppy platypus bag .....