Best method of laundering down filled pillows, is the one follwed by housewives on both sides of the pond for ages; removing the filling from the casing, launder each on their own, then put the filling back into the casing.
Rationale behind this was simple: down and feathers are made of protien and as they break down from use, make dust. It is this dust many people are allergic to, not the down by the way. Also since pillows cradle our heads as we sleep, they are subject to all and sundry sort of substances. From skin and hair oils, to cosmetics, to saliva, to blood, to god only knows what else. While a good ticking keeps much of this muck on the outside, depending upon how often pillow slips are laundered, stuff builds up and eventually gets inside.
The movement of our heads and fluffing up of the pillow also contribute to breaking down of the filling by mechanical wear.
Laundering a pillow by immersing the entire article in water, or washing machine does not allow the muck,dust, dust mites, and every thing else to come out of the pillow. Indeed since down by nature is water repellent, often it takes much effort to even get the filling wet. Another problem is rinsing, for even if one gets the detergent and water solution inside the pillow, rinsing clean is a bit of a problem
Down and feather filled pillows have been around for ages, to launder them the old fashioned way is simple:
First cut open or open a seam on one end of the pillow enough to take out the filling. Next place the pillow inside a large mesh bag or clean pillow case at least twice as large as the pillow. Carefully baste the pillow case to the pillow (you want to prevent an I Love Lucy moment where down goes flying all over, however if one can move the filling out of the pillow and still keep the pillow case from moving basting is not required), and turning the pillow upside down, shake/move the filling into the pillow case/mesh bag.
With the pillow ticking empty, one can wash it to death in hot water using a good enzyme detergent if required. Take the pillow slip/mesh bag full of down and either wash it in a large wash tub or bath tub using either a down wash product, or even a clean rinsing shampoo in warm water, rinse well and spin dry. You can then put the pillow case filled with down into the dryer and dry on low until it is dry. Because the down is in a large bag/case, much larger than the pillow, down as room to move and fluff up. As with down duvets, adding tennis balls, or those down fluffing things into the dryer will help deal with clumps. Either way, take the thing out and beat it/fluff every now and then, returning it to the dryer until dry.
When both the casing and down are dry, reverse the above to put the down back into the casing. Sew casing closed and viola! You have a totally clean and dust free down filled pillow. Before closing the pillow, one can add more down/feathers to make it more puffy.
Commercial dry cleaners,laundries that offer "pillow cleaning" service use pretty much the same method, however it is done by a machine and instead of water air and ozone are used. Bascially down is sucked out of a pillow case (or dumped), where it goes into a chamber that is like a dryer on air fluff. There the down is exposed to air and ozone to clean and fluff up the down. Once the cycle is completed the down is air blown into the empty pillow ticking.
L.