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Adventure School: The Lowdown on Sleeping Bags with Mountain Designs

The Low Down on Down Sleeping Bags – Zach Bostock

With the Australian summer bearing down, many adventurers will have started gathering their equipment, researching remote settings and preparing to get out into the great wide open.

Whether it’s an overnight hike, a weekend away by the campfire or an unmapped climb, one of the basic and most essential items on any gear list is the sleeping bag.

But with so many options on offer these days and with ever-increasing advancements in technology, determining which bag is best for your adventure can be a bit confusing at times.

One way of making the call is choosing a down sleeping bag – of which the benefits are many – over a synthetic.

But why is down the better option? To answer that, we spoke with Mountain Designs industrial designer Zach Bostock to get down to the basics.

Types of Down: Duck V Goose

To start with, Zach explained that down generally comes in four types – grey duck down, white duck down, grey goose down and white goose down.

“White down is generally more sort after so that the down is not seen through the fabric but the fact is both colours of duck down with the same loft (and we’ll talk about loft in a moment) will perform the same,” Zach said.

“Also, any discolouration through face fabrics is usually just grey down and not some horrible mould that has infiltrated your bag.

“In terms of duck versus goose, a good quality duck down can perform just as well, if not better, than goose down due to improved sorting methods.”

Loft Explained

Loft, as Zach continues, is also known as ‘Fill Power’ and is basically the technical way of talking about the expansion and fluffiness of the down, and the volume of the down clusters.

Loft values are measured from 450 to as high as 1200, generally across increments of 50, with the higher ratings meaning more air can be trapped within the clusters.

“What this means is greater insulation of your body heat,” Zach said.

“In addition, using a higher loft will also mean a better warmth to weight ratio as less down fill is needed in the bag itself.

“The loft rating can reduce over time, however it can be restored through care and maintenance.

“One trick is to tumble dry your bag on low or no heat with three tennis balls to break up the down clumps.”

Zach also explained that loft ratings of 1000 and higher are generally achieved using chemical treatments, therefore meaning the down is not a completely natural fibre any more.

Checking The Down Ratio

“A common misconception is that down sleeping bags are filled entirely with down but that’s not quite true; they tend to use a combination of down and feathers due to feathers sneaking in during the sorting process,” Zach said.

“As such, sorting methods vary in terms of efficiency.

“But irrespective, the higher the down to feather ratio is, the better loft rating that batch of down will achieve.

“Conversely, a low ratio of down to feathers will be very cheap, so when selecting a sleeping bag, check for the ratio and don’t be fooled by hang tags that simply call out the use of down.

“One of our primary focuses within the Mountain Designs product design team is quality so we generally use a minimum ratio rating of 80:20.”

Fortunately, Australian law requires the down ratio to be included on the care label so this is an easy specification to look out for when you’re in the shops selecting a product.

Hydrophobic Down…Say What?

A little help here Zach?

“Down can be treated with different coatings to improve its water-repelling qualities,” he explains.

“But it’s important to note that coating the down not make it waterproof, it only reduces the risk of down easily getting soaked.

“This is a great quality though if taking on the wilder elements while you adventure is your thing.

“Many brands will have their own version of hydrophobic down, for example at Mountain Designs we use Downtek™ in our Ultra Tek range.”

RDS Certification

According to Zach, the Responsible Down Standard is an independent, voluntary global standard to ensure animal welfare is considered.

“There is no legislation requirement to use this standard however any brand that adheres to it is recognised as adopting best practises in animal care,” he said.

“RDS certified down is traceable back to the original source where inspections have taken place to make sure the birds are looked after and that force feeding and live plucking are prohibited.


Like any product, there are some cons attached to using down.

“The biggest one is that down does not insulate when it is wet, but like I mentioned, there are treatments that can enhance that quality,” Zach said.

“Down is also a more expensive insulation but as is the case with most retail products, you get what you pay for.

“The fact is down has a greater warmth to weight ratio than synthetic, has good breathability and compressibility for packing, and is lightweight.”

Mountain Designs has recently released its 2017/18 summer range which includes the Ultra Tek 470 and Ultra Tek 900 down sleeping bags, designed specifically for multi-day hiking and alpine conditions for the wilder adventurer.

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