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At Forest Fundamentals™ we have been long users of the old British forces Millbank bags. However, these surplus bags are becoming increasingly harder to find. Most of the ones we did find, had seen years of use, and had most likely been used to filter oil and other nasty chemicals. So we decided to start hand-marking own!
The bag uses mostly the same dimensions as the original Millbank bags. However, we decided to go with a slightly thicker and denser 12oz canvas for better filtering capability. The bag is handmade using 12oz unbleached canvas. Unbleached canvas is not flawless but is more natural, safer for us and the environment.
For additional strength and durability, we have used V69 3ply Bonded Polyester Thread, the same thread used in tents and backpacks. Overlock double stitching has also been used on all of the seams of the bag for added strength and to avoid any raw edges. The overlock seams also provide another layer of filtering.
The Forest Fundamentals Millbank Bag is slightly larger than other bags on the market, making it easier to purify larger amounts of water at once. How-to instructions are also printed on the front of the bag. The printing uses non-toxic, food-grade, ink to make sure not to contaminate the filtered water. The instructions are also waterproof.
The bag comes with a large 550 ‘survival-cord’ lanyard. The cord includes strands of copper wire, fishing line, waxed jute, and parachute cord. All invaluable materials in the field, the cord can be used for repairing shoelaces, fishing, snares, shelter building, etc. The long lanyard avoids spillage caused by the bag swaying in strong winds and saves you time searching for a low-hanging branch!
We’ve also included a 210D Nylon waterproof carrying bag and a detailed instruction card. The bag makes it possible to quickly pack and transport the bag after use without soaking the inside of your pack!
• Handmade Millbank Bag
• Materials: 12oz unbleached Cotton canvas, 550 ‘survival-cord’, V69 3ply Bonded Polyester Thread, 210D Nylon
What is a Millbank Bag?
A Millbank Bag is a water filtration device that filters detritus. This detritus include sand, mud, silt, or other suspended particulate matter.
Removing all of the detritus before further sanitation is extremely important. Even if there are no waterborne diseases present, turbid water will irritate and cause damage to your digestive system.
In addition, turbidity can reduce the effectiveness and lifespan of other water sanitation systems including the popular Life Straw, for example.
However, a Millbank bag will not filter out pathogenic organisms, unless those organisms are attached to the detritus that is filtered. This is why additional forms of sanitation are required, including chemical or heat sterilisation. If your water source is already clear and has no detritus present then there is little advantage to using the Millbank bag. Although, few of us are lucky to find such water sources out in the wilderness!
How do you use a Millbank Bag?
1) Start by thoroughly soaking and massaging the bag underwater. This process will help saturate and loosen the bag's fibres. Otherwise, it can take hours for the water to filter through the bag.
2) Fill the bag to the brim, hang the bag up using the lanyard, and let the water drain out till the water is level to the black-white transition line (do not collect this water). This step ensures that you are only collecting the water that has drained through the bag (not excess water on the outside of the bag) from the saturation process.
3) Then, when the water level meets the transition line start to collect the water that is draining through.
In my experience, filtering a 1L bottle takes around 20mins, although sometimes it is a little faster. If boiling, it makes sense to collect the water straight into a metal pan or cup.
4) After the bag is empty, wash and dry the bag to avoid it going mouldy. Fold it up and tuck it neatly away! The bag will need cleaning from time to time. This is because the build-up of detritus can cause the filtration process to slow as it blocks the passage of water through the bag.
5) Sterilise! Remember, the Millbank bag is designed to aid further sterilisation, not to purify water completely.