The recent post re: Blizzard Bags resulted in the US distributors kindly sending one for examination. Longtime members will recall the group input on condoms for emergency canteen. A series of posts resulted in a remarkable document. I thought we would use this method again. I will post preliminary information so we all have the same vocabulary. If I make any mistakes forum members can point them out. We will first discuss the mechanisms of heat loss and generation, a history of the space blanket, and finally ( hopefully on what I can assemble) a review of the Blizzard Bag and any market competitors in term of materials etc. There are a few known and not so well known products that may be usefull additions to an emergency system we can discuss. Finally a appraisal of performance and specific use and value. I will also be invitng the makers to answer any questions.

Cody's book title says it all. We like this very thin microclimate of a wet 98.6 around us. We eat. Dieticians call this caloric intake; French toast,eggs,bacon and coffee, or a Mainstay bar spiced with tobasco sauce and Earl Grey Tea,in extremis Dead seagulls, ants and filtered water, Yum Yum The second method is external; a fire, radiated heat from rocks storing solar energy, chemical heat packs. The third option is kinetic energy, creating heat through exercise, aka flapping your arms while walking in circles, hopefully until you stumble upon a camp with a fire cookinig French Toast.

There is quite a good informative document about sleeping bag performance at

www.mammut.ch/mammut/uploadedFiles/Sleep%20Well_Pt1_E.pdf

It is quite a good introduction into the subject.

We have 5 mechanical processes, CCRRE- something I start to utter when I'm cold. Convection is air ( wind) on the skin speeding up evaporation beyond the optimal exchange to maintain that 98.6 Cody explains. Conduction is the loss of heat through contact with a colder surface. Think of the girl who turned you down for your first dance. Radiation is normal heat loss from the body. Think of it as a gas tank slowly emptied with normal driving and we know needs refilling ( french toast.) Respiration is heat loss through breathing. This is why people from cold climates have different noses from people in hot, at least until we all started dating pretty girls from all over and the irish great grandmother got hot and cold. Evaporation, a scientific term for perspiration AKA sweat: The normal cooling of our body to maintain, once more 98.9 degrees. Speed it up or slow it down and we are in trouble.

"Clothes make the man. Naked people have little or no effect on society."- Mark Twain. Everyone knows the 3 basic layers of clothing,right? We have an evaporative layer next to the skin to move perspiration off our body and avoid overheating and chilling. Next is insulation, materials that trap warm air. Finally we have a barrier layer to prevent rain and/or wind from further chilling and to keep that warm air and optional moisture in. All garments and shelter assemblies can be categorised into these three layers.

In 1964 Nasa developed a thin ( @ .20 Micron) plastic sheeting coated with powdered aluminum. We don't know if it was the same team that developed the Magnesium bar. The first use was in space suits with @ 27 layers.The material will reflect 80-90% ( depending on the source) of radiant body heat. Remember, these suits had external heating units in a closed and regulated environment. The 'Space Blanket' entered the civilian market as a lightwieght emergency item in an open and very unregulated environment called Mother Nature. It's that very compactness and wieght that make it an attractive option. But is it a blanket? A 6 point Hudson's Bay blanket is THICK. It has lots of air pockets ( loft)in all that wool to hold warm air.A single unit of space 'blanket' has none. Coupled with the fragile, almost single use material, space blankets are more properly space sheets. They make a good outer barrier to ward off wind and rain, or would if designed as an enclosed unit ( what Blizzard bags and a few others have done.)They have found some favour as PART of improvised shelters to improve campfire efficiency. The danger lies in their promotion as a convenient placebo. A person not interested in personal safety is going to think this handy, $3 item in the glove compartment is a Hudson's Bay Blanket. There's a anecdote about a cowboy caught in a Blizzard in the 1880s with only his thin 'fish' rain slicker for protection. He barely rode back to his ranch. His bunkmates asked him if the fish helped any? " If I had two of the blankety-blank things on I would have freezed to death." Is there a valid role and place for this material? We will try to find out with testing.

As for suggestions, I'd like to see it compared against a couple of benchmarks:

1) No bag.
2) A 'traditional' single walled bag as a control.

-john

I would second that suggestion but add a 3rd control,

3) A Rab Quantum Top Special bag at 300 gms and a Pacific Outdoor Equipment Insul Mat Uber Lite at 250 gms.

What would really be interesting would be test Army Ranger Ricks Mylar Blanket and 9 hr Candle method.

The bag arrived today. The unit is nicely vacuume packed in a durable, double layer of thick plastic bagging. I was about to cut it open with my knife and recalled the canadian crash where lack of knives kept needed gear inaccessable. I noticed a small slit in the packaging material highlighted in red. My nieghbor, a senior with arthritis was able to tear open the outer, and tougher bag with effort. I opened the second with a good tug. Then I read the instructions, brief but always helpfull to read first and it says " TEAR AT RED LINES TO OPEN." As an aside, if you are carefull and don't destroy the outer packaging a very tough water container can be fabricated by carefully resealing the top over fire. The bag itself is very generously sized lengthwise and my 6'2" frame will fit with full head coverage. The three layer laminate is sealed into a tube, the bottom gathered into a taper, glued and locked with a zip tie. It's not going anywhere and is very secure.Topside, there is a nice toggled drawstring of braided cord positioned on the lengthwise seal. The seal may cause a loss in insulation, not dissimilar to sleeping bags with the zipper covered by a flap. The instructions next tell you to CAREFULLY expand the bag by stretching it sideways. Well, mea culpa I again had my nieghbor help and her clenched fist tore off a palm sized layer of the outer laminate with a finger size hole fully tearing through the second and third. This did give a 'window' to constuction and revealed the horizontal, thread sized elastic and the two thick cellular construction. Next I'll climb inside.

As it happens, I won one of these in a competition when they first came out. Interesting idea that will help to keep you warm provided that you do everthing you can to help. Like get out of the *&^%$ wind! And put some insulation underneath you.


Space blankets do have their uses. Just so long as you treat them as a cheap expendable. They are above all things a vapour barrier. Weatherproof a shelter, cut up and use to line that hole you are going to hot rock boil some water or melt some snow in. Radar corner. Signal kit? Reflective layer for your desert survival shelter to help reflect the sun. Take four branches, one mylar blanket and some duct tape and hey presto! One Bloody Big Signal Mirror. One thing that they are is tough. Need to patch that hole in the hull? Double or triple a blanket over the hole and tape it down. You could even use one or two as a sail in a pinch. It might not last long, but so long as it does the job for just long enough, who cares? Use your imagination.

There seems to be an ethos on the forum of refusing to use something because its not exactly stellar at it's advertised purpose. I can live with loosing a nights sleep because they are not exactly quiet. Can't say the same thing about hypothermia.