JCB81 wrote:So for example product A is filled with X number of grams of 500 fill power and product B is filled with X number of grams of 800 fill power. So how many more grams of down would product A need to be the same warmth as product B?
wayno wrote:some down is chemically treated to resist moisture and will retain more loft when damp and dry out a lot faster..
it will be in the details about the item if it has this sort of down. and it won't be cheap
Orion wrote:wayno wrote:some down is chemically treated to resist moisture and will retain more loft when damp and dry out a lot faster..
it will be in the details about the item if it has this sort of down. and it won't be cheap
Premium down is expensive whether treated or not.
900 fill white goose down - $13.33 USD per ounce
850 fill HyperDRY goose down - $12.67 USD per ounce
andrewa wrote:As per Mark F, but be aware of proportion of quil to feather in down. A down with more quil will weigh marginally more than one without, and also be bulkier
I spoke at length with IDFL yesterday about down testing.
None of their tests stimulate real world testing. 900 fp in a test is going to be a pipe dream in the field, because they steam wash and dry the down to nearly zero humidity before doing the test. Ironically, this most recent iteration of test methods was designed to determine the maximum possible fill power for down rather than what it will look like in the field.
Interestingly as a side note, we did some 900 fp testing of down a few years ago on two manufacturer's 900 bags. We cut the bags open and sent them to IDFL. Neither made the claimed 900 spec (they tested 830-870 using the steam method). What was more dramatic was that when each down (which clearly came from different sources as evidenced by visual inspection) was subjected to 50% humidity, the differences were pretty dramatic. One bag tested at 770 fp, the other at 680 fp. It seems that at least these two sources of 900 down had feathers in it that were not resilient in response to humidity.
The kicker is that we ran the same test next to down taken from a manufacturer's 750 fp bag. at 50% humidity, the fp was 720. Why? It had more feathers that were stiff enough to preserve the loft in moist conditions.
simonm wrote:I haven't seen testing done on various fill powers response to moisture but anecdotally lower fill powers are less susceptible to loft collapse when exposed to moisture.
Edit: This is a quote from BPL;I spoke at length with IDFL yesterday about down testing.
None of their tests stimulate real world testing. 900 fp in a test is going to be a pipe dream in the field, because they steam wash and dry the down to nearly zero humidity before doing the test. Ironically, this most recent iteration of test methods was designed to determine the maximum possible fill power for down rather than what it will look like in the field.
Interestingly as a side note, we did some 900 fp testing of down a few years ago on two manufacturer's 900 bags. We cut the bags open and sent them to IDFL. Neither made the claimed 900 spec (they tested 830-870 using the steam method). What was more dramatic was that when each down (which clearly came from different sources as evidenced by visual inspection) was subjected to 50% humidity, the differences were pretty dramatic. One bag tested at 770 fp, the other at 680 fp. It seems that at least these two sources of 900 down had feathers in it that were not resilient in response to humidity.
The kicker is that we ran the same test next to down taken from a manufacturer's 750 fp bag. at 50% humidity, the fp was 720. Why? It had more feathers that were stiff enough to preserve the loft in moist conditions.
Moondog55 wrote:Another way to look at it
Fill weight Vs absorbed water weight
If all down absorbs the same percentage of water won't the higher FP down simply absorb a lower mass of water because there is less of it?
A wet bag is a wet bag and to be avoided but if it happened would you be better off in a bag using the higher lofting down?
Moondog55 wrote:What assumptions have you made re sizing when writing this program>
There being a huge difference between an XXS for the tadpole and an XXXL to fit me
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